US20060192221A1 - Methods, apparatus, and systems with semiconductor laser packaging for high modulation bandwidth - Google Patents
Methods, apparatus, and systems with semiconductor laser packaging for high modulation bandwidth Download PDFInfo
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- US20060192221A1 US20060192221A1 US11/409,938 US40993806A US2006192221A1 US 20060192221 A1 US20060192221 A1 US 20060192221A1 US 40993806 A US40993806 A US 40993806A US 2006192221 A1 US2006192221 A1 US 2006192221A1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/02—Structural details or components not essential to laser action
- H01S5/022—Mountings; Housings
- H01S5/0225—Out-coupling of light
- H01S5/02257—Out-coupling of light using windows, e.g. specially adapted for back-reflecting light to a detector inside the housing
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
- H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
- H01L2224/42—Wire connectors; Manufacturing methods related thereto
- H01L2224/47—Structure, shape, material or disposition of the wire connectors after the connecting process
- H01L2224/48—Structure, shape, material or disposition of the wire connectors after the connecting process of an individual wire connector
- H01L2224/481—Disposition
- H01L2224/48135—Connecting between different semiconductor or solid-state bodies, i.e. chip-to-chip
- H01L2224/48137—Connecting between different semiconductor or solid-state bodies, i.e. chip-to-chip the bodies being arranged next to each other, e.g. on a common substrate
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/30—Technical effects
- H01L2924/301—Electrical effects
- H01L2924/30107—Inductance
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/30—Technical effects
- H01L2924/301—Electrical effects
- H01L2924/3011—Impedance
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/30—Technical effects
- H01L2924/301—Electrical effects
- H01L2924/3025—Electromagnetic shielding
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/02—Structural details or components not essential to laser action
- H01S5/022—Mountings; Housings
- H01S5/02208—Mountings; Housings characterised by the shape of the housings
- H01S5/02212—Can-type, e.g. TO-CAN housings with emission along or parallel to symmetry axis
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/02—Structural details or components not essential to laser action
- H01S5/022—Mountings; Housings
- H01S5/0225—Out-coupling of light
- H01S5/02251—Out-coupling of light using optical fibres
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
- H01S5/068—Stabilisation of laser output parameters
- H01S5/0683—Stabilisation of laser output parameters by monitoring the optical output parameters
Definitions
- the invention relates generally to the field of optoelectronic device packaging. Particularly, the invention relates to semiconductor laser packaging.
- FIG. 1 is a block diagram of a typical optical data link.
- FIG. 2 is a functional block diagram illustrating the impedances around a packaged semiconductor laser including the impedance controlled circuit.
- FIGS. 3A-3D are magnified views of an embodiment of a packaged semiconductor laser including the impedance controlled circuit.
- FIG. 4A is a magnified cross-sectional side view of an alternate embodiment of the packaged semiconductor laser including the impedance controlled circuit.
- FIGS. 4B-4C are magnified views of another alternate embodiment of the packaged semiconductor laser including the impedance controlled circuit.
- FIGS. 5A-5B are magnified views of the impedance controlled circuit.
- FIGS. 6A-6B are magnified perspective views of a pair of different bond wires to further reduce impedance.
- FIGS. 7A-7C are magnified views of a dielectric feedthrough to provide a nominal input impedance at the pin.
- FIG. 8A is an exploded view of a semiconductor laser package without the can lid to illustrate the assembly of the pin and feedthrough into the header.
- FIG. 8B is a magnified cross-sectional side view of an assembled pin and feedthrough in the header.
- FIG. 9 is a bottom view of the packaged semiconductor laser having standard pin spacing.
- FIG. 10A is a magnified top view of a first alternate header with a first altered pin spacing for another embodiment of the packaged semiconductor laser.
- FIG. 10B is a bottom view of the packaged semiconductor laser having the first altered pin spacing of FIG. 10A .
- FIG. 11A is a magnified top view of a second alternate header with a second altered pin spacing and a first submount modified thereto for another embodiment of the packaged semiconductor laser.
- FIG. 11B is a bottom view of the packaged semiconductor laser having the second altered pin spacing of FIG. 11A .
- FIG. 12A is a magnified top view of the second alternate header with the second altered pin spacing and a photodiode and a second submount modified thereto for another embodiment of the packaged semiconductor laser.
- FIG. 12B is a magnified top view of the second alternate header with the second altered pin spacing and a third submount modified thereto separate and apart from the photodiode for another embodiment of the packaged semiconductor laser.
- FIGS. 13A-13B illustrate an alternate thin outline package including an alternate header and variable dimensions related thereto.
- FIG. 14A is a block and ray diagram illustration of automatic power control of a surface emitting semiconductor laser and in response to power monitoring by a photodiode.
- FIGS. 14B-14C illustrate alternate embodiments of the material layers of the window of the slanted can or cap.
- FIG. 15A is an exploded view of an first exemplary fiber optic module including an optical block to illustrate a higher order assembly of the packaged semiconductor laser.
- FIG. 15B is a cutaway side view of the packaged semiconductor laser mechanically coupled to the optical block illustrated in FIG. 15A .
- FIG. 16A is an exploded view of a second exemplary fiber optic module including a fiber optic plug with a lens to illustrate a higher order assembly of the packaged semiconductor laser.
- FIG. 16B is a cutaway side view of the packaged semiconductor laser mechanically coupled to the fiber optic plug including a lens as illustrated in FIG. 16A .
- a high-performance, yet low-cost packaging scheme for 10 gigabit per second (Gbps) vertical cavity surface emitting lasers (VCSEL) is disclosed.
- the semiconductor laser is packaged in a thin outline (TO) based package with added features for high-speed performance and laser power monitoring for automatic power control (APC).
- the packaged semiconductor laser may be incorporated into an optical transceiver or fiber optic module of an optical data link or an optical communication system.
- An optical data link includes an optical transceiver 100 A, an optical transceiver 100 B, and at least one fiber optic cable 102 .
- Each of the optical transceivers 100 A and 100 B are bi-directional optical transceivers to interface to the at least one optical fiber 102 .
- the elements of each optical transceivers 100 A and 100 B may be substantially similar.
- the at least one optical fiber 102 includes a first plug 104 A and a second plug 104 B.
- the typical block functional elements of the optical transceiver 100 A includes a nose or fiber optic receptacle 110 , an optical block 112 , optical electronics 114 , transmit and receive electronics 116 , and pins, terminals, pads, or connectors 118 .
- the nose or fiber optic receptacle 110 receives the fiber optic plug 104 A of the at least one optical fiber 102 .
- the nose mechanically couples to the optical fiber 102 .
- the nose may have an opening to receive various types of fiber optic plugs including simplex and duplex type plugs.
- the fiber optical receptacle 110 holds the plug 104 A in alignment with the optical block.
- the optical transceiver 100 A may couple to a host system 106 .
- the host system 106 may include poles, terminals, pads, or connectors 120 to couple to the pins, terminals, pads, or connectors 118 respectfully of the optical transceivers 100 A.
- the pins, terminals, pads, or connectors 118 of the optical transceiver 100 A is for coupling to the host system 106 .
- the optical block 112 is for coupling light between the optical electronics 114 and the optical fiber 102 .
- the optical block 112 may include one or more lenses or light bending elements to couple light between the optical fiber 102 and the packaged optoelectronic components 114 .
- the packaged optoelectronic components 114 may transduce between electrical signals and optical signals.
- the packaged optoelectronic components 114 may include a packaged semiconductor laser, a packaged semiconductor detector, or both.
- the transmit and receive electronics 116 appropriately controls the packaged optoelectronic components 114 to generate lights signals or receive light signals as well as electrical signals at the pins, terminals, pads, or connectors 118 .
- a thin outline (TO) based package In packaging a semiconductor laser, a thin outline (TO) based package has been used for two and one half Gbps or lower data-rate lasers in the various telecommunication and data-communication applications in the past few years.
- a VCSEL die is mounted in the center of the TO header, with its electrical connection directly on a header's posts.
- the length of the wire bond in this case typically ranges from one and one-half millimeters (mm) to two and one-half mm or longer. This results in a critical electrical path which is long, and therefore has a relatively large inductance.
- a VCSEL packaged in this manner may typically have a modulation bandwidth of about two to four gigaHertz (GHz). In some cases, five to seven GHz may be achieved, depending on the arrangement of the wire bonding. However, the current TO structure and wire bonding scheme limits performance below ten Gbps performance.
- the packaged semiconductor device can include an impedance-controlled circuit is combined with the design and selection of the dimensions and materials of the package along with the position and electrical connections to provide impedance matching in a number of embodiments.
- the dimensions and materials of the package may be designed and selected to provide impedance matching along with the positioning and electrical connections made to the optoelectronic device in the package without the impedance controlled circuit.
- the impedance-controlled circuit 202 is coupled between the semiconductor laser 200 (such as a VCSEL) and the TO-header post 204 .
- the impedance-controlled circuit 202 functions to reduce impedance in the ordinary interconnect to the semiconductor laser when a standard package is used.
- the Minimized interconnections 201 and 203 between impedance-controlled circuit 202 and the semiconductor laser 200 and TO header post 204 are formed respectively with reduced impedances.
- the impedances Z 1 and Z 2 of impedance controlled circuit 202 are impedance matched to the impedance Z L of semiconductor laser 200 and the feedthrough impedance Z F as seen at the TO header post 204 or pin 205 , respectively.
- the impedances Z 1 and Z 2 of the impedance controlled circuit 202 are equal to each other and to the impedance Z L Of semiconductor laser 200 and the feedthrough impedance Z F .
- a nominal impedance for the semiconductor laser 200 at a given frequency or frequency range is fifty ohms.
- the design of the TO package is slightly adjusted so that the nominal feedthrough impedance Z F matches the nominal impedance of the semiconductor laser 200 .
- Z F is also fifty ohms at the given frequency or frequency range.
- the design of the impedance controlled circuit 202 provides nominal impedances for Z 1 and Z 2 which are the same to match that of the semiconductor laser 200 .
- Z 1 and Z 2 which are equal are also fifty ohms at the given frequency or frequency range.
- the impedance-controlled circuit 202 may additionally be used to compensates for what otherwise might be a slight mismatch between the impedances of the TO-header post and the semiconductor laser including the interconnect there-between and the pin 205 .
- Z 1 and Z 2 may be unequal or equal at the nominal frequency, but provide compensation at other frequencies.
- the impedance-controlled circuit 202 may compensate for resistance, inductance, and capacitance.
- the packaged semiconductor laser may also be referred to herein as a packaged transmitter because they are used in communication systems to transmit data signals using light signals.
- the packaged semiconductor laser 300 includes a slanted window can or cap 312 , a header 314 , and pins or leads 316 of a device package.
- the device package is a thin outline (TO) type of device package and the slanted window can or cap 312 is a slanted window TO can or cap and the header 314 is a TO header.
- the header 314 generally provides mechanical support and electrical connections to one or more pins.
- the slanted window can or cap 312 generally provides a hermetic seal to the header 314 to enclose a device, allows a portion of laser light to pass out through a window and from the package, and reflects a portion of the laser light back to a photodetector 330 for power monitoring and automatic power control of the semiconductor laser. That is, the window of the slanted window can is partially transparent and partially reflective to the laser beam emitted from the semiconductor laser. The reflected light on the photodetector generates a monitor current for control of the output power from the semiconductor laser.
- the slanted window can 312 includes a lip 313 , a slant lid or angled top 317 , a glass window 318 , and a window opening 319 as shown and illustrated.
- the lip 313 of the slanted window can 312 is for sealing to a surface of the header 314 .
- the glass window 318 allows a portion of the laser beam to pass through it.
- the window opening 319 allows the portion of the laser beam to exit out from the package 300 into space or into a fiber optic cable or other optical transmission media.
- the slanted window can 312 may further include a can tab that mates with a slot in the header 314 for proper alignment of the slant lid 317 and the slant window can 312 with the header 314 .
- a can tab and slot are described below and illustrated in other Figures herein.
- the glass window 318 is hermetically sealed to the inside surface of the slanted window can 312 . More particularly, the glass window 318 is hermetically sealed to the inside surface of the slant lid 317 of the slanted window can 312 .
- the glass window 318 may have a circular shape and a diameter to cover over the window opening 319 of the slant lid 317 to seal out dust and dirt.
- the hermetic seal between the glass window 318 and the slanted window can 312 further prevents moisture from seeping inside into the packaged semiconductor laser.
- a semiconductor photodiode or photodetector 330 Inside the packaged semiconductor laser 300 is a semiconductor photodiode or photodetector 330 , a semiconductor laser 332 such as a vertical cavity surface emitting laser (VCSEL), and the impedance controlled circuit 202 .
- the photodiode is a PIN type of photodiode.
- the photodiode 330 and the impedance controlled circuit 202 are attached to a surface of a header flange 334 of the header 314 .
- the impedance controlled circuit 202 couples to a header post 204 of one of the pins 316 which extends above the header.
- the impedance controlled circuit 202 further couples to the semiconductor laser 332 .
- the photodiode 330 has a submount portion 331 (better illustrated in FIGS. 3C and 3D ).
- the semiconductor laser 332 is attached to a top surface of the submount portion 331 of the photodiode 330 .
- the submount portion 331 of the photodiode 330 may include vias to electrically couple between the header flange 334 and a substrate surface of the VCSEL 332 .
- the submount portion 331 may be a submount separate and apart from the photodiode 330 .
- FIG. 3C a perspective view of the packaged semiconductor laser 300 without the slanted window can 312 and bond wire interconnects is illustrated.
- the semiconductor laser 332 is attached to a top surface of the submount portion 331 of the photodiode 330 .
- the submount portion 331 of the photodetector 330 locates the semiconductor laser die 332 in position within the package in x, y and z coordinates.
- the semiconductor laser 332 includes a surface emitting area 342 and an active region (not shown) formed of one or more quantum well structures.
- the photodiode 330 For transducing light or photons into an electrical signal or electrons, the photodiode 330 includes a light detection area 340 opposite the submount portion 331 .
- the light detecting area 340 (acting as a photodetector) is a monitoring photodetector to detect and monitor the output power of the semiconductor laser 332 .
- FIG. 3D is a magnified top view of an embodiment of the packaged semiconductor laser 300 without the slanted window can 312 assembled thereto.
- bond wire interconnects generally referred to as 360
- bond wires are illustrated forming electrical connections between elements of the packaged semiconductor laser 300 .
- the impedance-controlled circuit 202 is located between the semiconductor laser 332 and the TO-header post 204 B.
- the impedance-controlled circuit 202 includes at least one impedance-control line 370 fabricated on top of a printed circuit board 372 .
- one end of the at least one impedance control line 370 (i.e., a transmission line) of the impedance controlled circuit 202 will be wire-bonded to the TO-header post 204 B to receive a driving current for the semiconductor laser 332 from the pin 316 B.
- An opposite end of the at least one impedance control line 370 (i.e., a transmission line) of the impedance controlled circuit 202 will be wire-bonded to the semiconductor laser die 332 to provide the drive current thereto.
- a wire bond 360 A couples to the header post 204 B at one end and the at least one impedance control line 370 at an opposite end.
- a wire bond 360 B couples to a bonding pad of the semiconductor laser 332 at one end and the at least one impedance control line 370 at an opposite end.
- a wire bond 360 C couples to a bonding pad of the semiconductor photodetector 330 at one end and the header post 204 A at an opposite end.
- the submount 331 may include a large bonding pad 343 to which multiple wire bonds may be coupled.
- wire bonds 360 D 1 and 360 D 2 couple to the header flange 334 at one end and the bonding pad 343 at an opposite end.
- Wire bonds 360 E 1 and 360 E 2 couple to a pair of pads of the semiconductor laser 332 at one end and the bonding pad 343 at an opposite end.
- the header flange 334 is coupled to at least one of the pins 316 . Typically the header flange is grounded to a source of ground or a low level voltage supply.
- Each of the wire bonds 360 has an impedance associated with it.
- the impedance of a bond wire is mostly inductance.
- the resistance in the bond wires are usually negligible but for the case of high currents.
- the shorter the length of the bond wire the less inductance and resistance there is in the bond wire.
- the larger the diameter of the bond wire the less inductance and resistance there is associated with it.
- Coupling two bond wires in parallel together, such as bond wires 360 D 1 and 360 D 2 for example lower the resistance and inductance of the overall connection between two points because the resistance and inductance of each are placed in parallel.
- the positioning of the semiconductor laser 332 , the impedance controlled circuit 202 , and the header post 204 B are such to minimize the lengths of the bond wires 360 A and 360 B and their associated impedances with respect to the at least one control line 370 .
- the impedance controlled circuit 202 is die attached onto a top surface of the header flange 334 relatively close to the header post 204 B to minimize the length of bond wire 360 A.
- the submount 331 i.e.
- photodetector 330 including submount portion 331 is die attached onto a top surface of the header flange 334 relatively close to the impedance controlled circuit 202 and the semiconductor die 332 is die-attached onto a top surface of the submount 331 and located next to an edge thereof closest to the impedance controlled circuit 202 to minimize the length of bond wire 360 A.
- the heights relative to the header flange 334 of the top surface of the semiconductor laser 332 and the top surface of the at least one control line 370 to which wire bond 360 B is formed is substantially equal to further minimize the length of the bond wire 360 B.
- the heights relative to the header flange 334 of the top surface of the header post 204 B and the top surface of the at least one control line 370 to which wire bond 360 A is formed is substantially equal to further minimize the length of the bond wire 360 A.
- one contact point of the at least one control line 370 is made as close as possible to the header post 204 B and another contact point of the at least one control line 370 is made as close as possible to a wire bond pad on the semiconductor laser 332 .
- the elements are placed so that the at least one impedance control line 370 is made as close as possible to the header post 204 B and the semiconductor laser 332 so that the bond wires are kept as short as possible.
- a thicker bond wire can be used as the bond wires 360 as is discussed further below.
- extra wire bonding may be used to reduce inductance when added in parallel and in the case larger currents are expected.
- extra bond wires 360 D 1 and 360 D 2 are used to couple the contact 331 to the header flange 334 and couple large currents to ground. In these cases, the length of the wire bonding is greatly reduced to minimize inductance introduced by the bond wire without any impedance matching provided by the impedance control circuit 202 .
- FIG. 4A a magnified cross sectional right side view of an another embodiment is illustrated.
- FIG. 4A illustrates a submount 331 ′, a semiconductor laser 332 ′, and the impedance controlled circuit.
- the submount 331 ′ has one or more vias 402 to electrically connect a top large bonding pad or surface contact area 343 ′ to a bottom surface contact area 406 of the submount.
- the bottom surface contact area 406 is die attached to the header flange 334 using a conductive epoxy to mechanically and electrically couple the bottom surface contact area 406 to a top surface of the header flange 334 .
- the impedance controlled circuit 202 includes a ground plane 470 which is also die attached to the header flange 334 using a conductive epoxy to mechanically and electrically couple thereto.
- a bottom surface of the semiconductor laser 332 ′ in this case has bottom contacts 414 .
- the bottom contacts 414 of the semiconductor laser 332 ′ couple to the surface contact area 343 ′ of the submount 331 and electrically connect through the vias 402 to the header flange 334 .
- Optional vias 412 in the semiconductor laser 332 ′ may be used to route an upper connection to the bottom contacts 414 in order to make such a connection.
- This embodiment eliminates the wire bonds 360 D 1 , 360 D 2 , 360 E 1 and 360 E 2 illustrated in FIG. 3D to further reduce inductance in the connections to the semiconductor laser 332 .
- FIG. 4A also illustrates how the submounts described herein elevate and mechanically support the semiconductor laser die above the header flange at a level near the top of the header posts. Thus being at the same height, wire bonds may be made between the semiconductor laser die and the top of the header posts with minimal lengths.
- FIG. 4B a magnified top view of yet another embodiment for the packaged semiconductor laser is illustrated.
- FIG. 4B illustrates a top view of a submount 331 ′′ of a photodetector 330 ′′, the semiconductor laser 332 ′, the impedance controlled circuit 202 and a conductive block 422 .
- the wire bonds 360 E 1 and 360 E 2 illustrated in FIG. 3D have been eliminated by using the optional vias 412 in the semiconductor laser 332 ′.
- the bottom contact 414 of the semiconductor laser 332 ′ couples to the large bonding pad or surface contact 343 ′′ of the submount 331 ′′.
- wire bonds 360 D 1 , and 360 D 2 illustrated in FIG. 3D have been eliminated by conductively epoxying a top surface of the conductive block 422 to the surface contact 343 ′′ of the submount 331 ′′ and a bottom surface of the conductive block 422 to the header flange 334 .
- the conductive block 422 is formed out of a conductive material such as metal, an alloy, or other conductive material.
- the conductive block 422 may be rectangularly shaped as illustrated, cylindrically shaped, or take on another shape so that the conductive block 422 has a top surface 423 to which a conductive epoxy could adhere and form an electrical connection thereto.
- a conductive epoxy 444 electrically couples the top surface 423 of the conductive block 422 to the surface contact 343 ′′.
- an edge of the surface contact 343 ′′ extends out to substantially meet an edge of the submount portion 331 ′′ of the photodetector 330 ′′ and the height of the conductive block 422 is substantially similar to the height of the submount portion 331 ′′.
- the conductive block 422 is approximately level with the surface contact 343 ′′.
- the conductive epoxy 444 electrically couples to the surface contact 343 ′′ at the extended edge of the surface contact 343 ′′.
- FIG. 4C a magnified cross-sectional front side view of the embodiment of FIG. 4B is illustrated.
- the photodetector 330 ′′ and the conductive block 422 are die attached to the header flange 334 as close as possible to each other leaving only a small gap 448 .
- a bottom surface 424 of the conductive block 422 is epoxied using the conductive epoxy 444 to the header flange 334 . This mechanically and electrically couples the conductive block 422 to the header flange 334 .
- a bottom contact 406 ′ of the photodetector 330 ′′ may also be conductively epoxied to the header flange 334 .
- the conductive block 422 When mounted to the header flange 334 , the conductive block 422 is approximately level with the surface contact 343 ′′ of the submount portion 331 ′′ of the photodetector 330 ′ as is illustrated.
- a strip of conductive epoxy 444 is poured onto both the top surface 423 of the conductive block 422 and the surface contact 343 ′′ of the submount 331 ′′ across the gap 448 .
- the conductive epoxy effectively provides a bridge connection across the gap 448 .
- the conductive epoxy 444 electrically couples to the surface contact 343 ′′ at the extended edge of the surface contact 343 ′′.
- the width of the conductive epoxy 444 along the edge of the surface contact 343 ′′ may be adjusted to vary the impedance of the connection made.
- a wider strip of conductive epoxy further reduces the impedance of the bridge connection over the gap 448 .
- the semiconductor laser 332 ′ is shown illustrated in the embodiment of FIGS. 4B-4C using a bottom connection 414 and possibly an optional via 402 if necessary. However, the semiconductor laser 312 with top bonding pads and bond wires 360 E 1 and 360 E 2 as illustrated in FIG. 3D may be used to couple the laser to the surface contact 343 ′′.
- FIGS. 5A and 5B magnified views of the impedance controlled circuit 202 are illustrated.
- FIG. 5A illustrates a top magnified view of the impedance-controlled circuit 202 .
- FIG. 5B illustrates a side magnified view of the impedance controlled circuit 202 .
- the at least one impedance control line 370 is formed on a top surface of the printed circuit board 372 .
- the printed circuit board 372 of the impedance-controlled circuit 202 includes a ground plane 470 having a surface which is die attached by a conductive epoxy 502 to a top surface of the header flange 334 .
- the header flange 334 electrically couples to the ground plane 470 .
- the printed circuit board 372 is a dielectric and depending upon its selection may have different dielectric constants.
- the ground plane is for the at least one impedance-control line 370 .
- the at least one impedance control line 370 may be formed using microstrip line or transmission line techniques. In either case, the impedance control line 370 is a wave guide to the signal that propagates across it.
- the impedance control line 370 may include circuit element equivalents formed using microstrip line techniques or transmission line techniques.
- the at least one impedance control line 370 may generally be considered to have a length L, a width W, and a thickness T. Variations in width, length, and thickness of the least one control line 370 may occur from one end to another in order to achieve a desired impedance effect.
- a plurality of impedance control lines 370 may be coupled together in different ways to achieve desired impedances in the impedance controlled circuit 202 .
- other discreet components may be coupled to the printed circuit board 373 to provide impedance compensation.
- the discreet components may be chip resistors, chip capacitors, or chip inductors.
- the printed circuit board 372 may be a laminate of material layers of a standard laminate grade (e.g., Rogers FR-xx, G-xx, and GPO-.xx) or a solid material such as ceramic. Pairs of the material layers for the printed circuit board 372 may be paper/phenolic, paper/epoxy, glass/epoxy, glass/phenolic, glass/melamine, glass/polyester, and teflon fiberglass.
- the material layers establish an associated dielectric constant for the printed circuit board and a thickness which effects the impedance of the at least one impedance control line 370 .
- the at least one impedance control line 370 is formed of a conductive material, such as a metal, and has dimensions of a length, a width, and a thickness. These dimensions may also be a factor in the impedance of the at least one impedance control line 370 .
- the type of conductive material may also be a factor in the impedance of the at least one impedance control line 370 .
- the conductive material may be a metal such as gold, copper, silver, titanium, and aluminum, an alloy thereof, or another conductive element such as silicon, germanium, or carbon.
- the signal wavelength in free space i.e., ) which is a function of the signal frequency is also a factor to consider in designing the impedance of the at least one impedance control line 370 .
- the length dimension of the at least one impedance control line 370 is often proportional to a fraction of the wavelength of the signal in free space.
- the impedance controlled circuit 202 provides a nominal impedance at a given frequency or over an average frequency range.
- the nominal impedance of the impedance control circuit 202 is fifty ohms at ten gigaHertz (i.e., ten Gbps) in a preferred embodiment. It is desirable that the nominal impedance of the impedance controlled circuit 202 ; the feedthrough 345 B and/or feedthroughs 345 A- 345 B; and the semiconductor laser 332 match.
- FIGS. 6A and 6B perspective views of different types of bond wires are illustrated.
- a standard circular cylindrical bond wire 360 is illustrated.
- the diameter of the circular cross section of the bond wire 360 is d.
- the diameter d is typically twenty-five microns wide.
- the inductance and impedance of the bond wire 360 may be reduced by using a larger diameter bond wire where d is greater than thirty microns for example.
- the diameter d may be from thirty to one hundred fifty microns or more for example to reduce the induction and impedance therein.
- the dimensions of the bonding pads of the devices may need to be increased accordingly.
- the ribbon bind wire 360 ′ is a rectangular cylindrical bond wire.
- the rectangular cross section of the ribbon bond wire 360 ′ has dimensions of a height h and a width w.
- the width w of the ribbon bond wire 360 ′ is significantly greater than the height h in order to reduce the inductance and impedance of the bond wire. Assume for example that the height h may be the same as the standard diameter of the circular bond wire, twenty-five microns.
- the width w of the ribbon bond wire 360 ′ is significantly greater than the height h, such as a multiple or four or five times the dimension of the height h for example.
- the width w of the ribbon bond wire 360 ′ may be on the order of one-hundred to one-hundred-twenty-five microns.
- the dimensions of the bonding pads of the devices may need to be increased accordingly.
- the ribbon bond wire 360 ′ may replace one or more of the bond wires 360 illustrated in the Figures (e.g., bond wires 360 A- 360 E 2 illustrated in FIG. 3D ).
- Feedthrough 345 used for at least feedthrough 345 B are illustrated.
- Feedthrough 345 referred to herein generally represents feedthroughs 345 A and 345 B.
- Feedthrough 345 as illustrated in a magnified top view of FIG. 7A is shaped similar to a hollow circular cylinder with a thickness th.
- the feedthrough 345 has a radius R 1 which is in the inner radius of the hollow cylinder and a radius R 2 which is the outer radius of the hollow cylinder.
- the empty solid cylinder 701 of radius R 1 is where a portion of the pin 316 would otherwise fill.
- the radius R 1 may be considered to be substantially equal to the radius of the pin.
- the radius R 2 conforms to a solid cylinder that fills a cylindrical opening in the header 314 .
- the feedthrough 345 has a height H FT which corresponds to the depth of a cylindrical opening in the header 314 and header flange 334 .
- the depth of the cylindrical opening is the equivalent of the thickness of the header 314 and the header flange 334 .
- the height H FT of the feedthrough 345 may be altered by varying the thicknesses of the header 314 and the header flange 334 in order to provide a desired nominal feedthrough impedance value Z F .
- the feedthrough impedance value Z F of one or more pins of the TO-header can be designed according to the impedance of the semiconductor laser 332 . It is desirable that the nominal impedance of the feedthrough 345 B match the nominal impedance of the semiconductor laser 332 .
- FIG. 7C illustrates a magnified perspective view of the feedthrough 345 which better illustrates its shape being described as a hollow circular cylinder.
- FIG. 8A an exploded view illustrating the assembly of the pin 316 A, a glass cap 802 , and the feedthrough 345 A to the header 314 is illustrated.
- the pin 316 A may first be inserted into the center of the cylindrical opening 804 in the header 314 and header flange 334 .
- a desired molten dielectric is poured around the pin to fill in the cylindrical opening 804 and form the feedthrough 345 A around the pin 316 A.
- Molten glass is then poured onto the base of the package to cover around the bottom of the feedthrough around the pin and onto a bottom side of the header 314 .
- the molten glass is allowed to cool into a solid state and forms a hermetic seal around the pin and the feedthrough to keep dirt and moisture out of the inside of the package.
- press fitting of solids are used with the glass cap being hermetically sealed at the end.
- the pin 316 A is press fit into the cylindrical opening 701 of a solid feedthrough 345 A.
- 316 A is press fit into the opening 804 in the header 314 and header flange 334 .
- a cylindrical opening 801 in the center of the glass cap 802 is slid over the pin at the outer end opposite the post end 204 .
- a solid glass cap 802 is slid along the pin 316 A to meet the bottom of the header 314 .
- the outer radius of the glass cap is larger than the outer radius R 2 of the feedthrough in order to seal over the opening 804 .
- the inner radius of the glass cap 802 is near the radius of the pin 316 .
- the glass cap 802 can then be heated in a number of ways to hermetically seal around the opening 804 and the pin 316 A.
- FIG. 8B a magnified cross-section view of the final assembly in either case is illustrated.
- the pin 316 A is inserted into the cylinder 701 of the feedthrough 345 A to form the header post 204 A.
- the feedthrough 345 A is inserted into the opening 804 in the header 314 and the header flange 334 .
- the glass cap 802 hermetically seals around opening 801 at the pin 316 A and around the opening 804 and the feedthrough 345 A in the bottom of the header 314 as illustrated.
- the pin 316 A being a metal provides a conductive path to a terminal of a device that may be mounted inside the package.
- the pin 316 A may have an impedance (i.e. resistance, inductance, and capacitance) associated with it.
- the feedthrough 345 A is formed of a dielectric material to insulate the pin from shorting to the header and header flange and to provide impedance matching.
- the dielectric constant of the feedthrough material is important to provide impedance matching.
- the feedthrough impedance Z F is seen as a result of the pin extending through a grounded header 314 and header flange 334 . This is similar to a coaxial cable with a center pin and an outer ground cylindrical shell used in seventy five ohm coaxial cable.
- the feedthrough 345 can be designed in its dimensions (i.e., R 1 and R 2 or th; H FT ) and by the selection of dielectric materials for a given pin to provide a desired nominal feedthrough impedance Z F at a frequency or over a range of frequencies.
- the selection of the pin diameter and conductive material can also be used to alter the feedthrough dimension R 1 and influence the feedthrough impedance.
- the selection of the thickness of the header and header flange can also be used to alter the feedthrough dimension H FT and influence the feedthrough impedance.
- the header's feedthrough impedance Z F should be designed to match the impedance Z L of the semiconductor laser 332 to minimize reflections at high frequencies caused by impedance mismatches.
- the header's feedthrough impedance Z F is the impedance seen as a pin 316 feeds up through the feedthrough 345 into the header 314 and the header flange 334 and extending out into the header post 204 .
- the feedthrough impedance can be designed with proper selection of materials and sizing of the feedthroughs 345 .
- FIG. 9 a bottom view of a pin-out for a three and a four pin header is illustrated.
- Pins 316 A and 316 B feed through into the package to make electrical connections to optoelectronic devices such as the semiconductor laser 332 and the monitoring photodiode 330 .
- In line with the center C of the package and perpendicular to the header is an optical axis of the light output 342 of the semiconductor laser 332 .
- the pins 316 A and 316 B are equally offset from the center C in alignment on a y axis.
- pins 316 C are illustrated. Pins 316 C do not feedthrough past the header and into the inner chamber of the package. Pins 316 C mechanically and electrically couple to the bottom of the header 314 . Pins 316 C are electrically coupled through the header 314 to the header flange 334 . Pins 316 C are usually coupled to ground in order to ground out the header 314 , header flange 334 , and the can or cap 312 .
- feedthrough type pins 316 A and 316 B are discussed without any further discussion of pins 316 C. It being understood that at least one pin 316 C exists that couples to the bottom of the header 314 .
- the header flange 334 of the header 314 may be altered by moving the pins 316 while maintaining the desired dimensions of the feedthroughs 345 for impedance matching purposes.
- the feedthrough type pins are moved closer to center in order to reduce bond wire length and their inductance for better high speed performance without use of an impedance controlled circuit 202 .
- the photodiode and the semiconductor laser are generally mounted within the device package as is discussed previously with reference to FIG. 3D and discussed below with reference to FIGS. 13A-13B .
- the modified header flange 334 ′ has one pin 316 B and feedthrough 345 B offset and moved closer to the semiconductor laser 332 while the other pin 316 A and feedthrough 345 A remain at the same standard position. From a bottom view with the header flange 334 ′ flipped around sideways, the pins 316 appear spaced apart as illustrated in FIG. 10B . Pin 316 B is offset closer to center C than pin 316 A.
- a bond wire 360 F couples at one end to the header post 204 B and at an opposite end to a pad of the semiconductor laser 332 . With the pin 316 B and feedthrough 345 B offset and moved closer to the semiconductor laser 332 , the bond wire 360 F is shorter than it might otherwise be. The reduction in length of the bond wire reduces the inductance there between.
- the feedthrough 345 B is properly designed so that the feedthrough impedance Z F matches the input impedance Z L of the semiconductor laser 332 .
- FIGS. 11A and 11B a modified header flange 334 ′′ of the header 314 ′′ is illustrated.
- the modified header flange 334 ′′ has both pins 316 A and 316 B and both feedthroughs 345 A and 345 B moved closer to the center C of the package as illustrated in FIG. 11B .
- Pins 316 A and 316 B have the same offset from center C along the y axis.
- the bond wire 360 F couples at one end to the header post 204 B and at an opposite end to a pad of the semiconductor laser 332 .
- the reduction in length of the bond wire 360 F reduces its inductance.
- the feedthrough 345 B is properly designed so that the feedthrough impedance Z F matches the input impedance Z L of the semiconductor laser 332 .
- Feedthrough 345 A may be similarly designed to match the input impedance Z L of the semiconductor laser 332 or otherwise designed to match the output impedance of the photodiode. Impedance matching with the photodiode is not as important as it is with the semiconductor laser.
- the devices inside the package can be modified to maintain the center of the laser output 342 .
- the submount area 331 of the photodiode 330 is modified to maintain the center of the laser output 342 .
- a notch 1100 is cut into the submount portion 331 ′′′′ of the photodiode 330 ′′′′ so that it accepts the tighter position of the post 204 A and pin 316 A.
- a bond wire 360 C′ is coupled between the post 204 A and the photodiode 330 ′′′′. The length of bond wire 360 C′ is also reduced and lowers its inductance as a result. Otherwise similar labeled elements are similar to those of FIG. 10A .
- FIGS. 12A-12B alternate embodiments to the submount modification to that of FIG. 11A are illustrated with the same pin and header configuration of the device package.
- a thin submount 331 v and photodiode 330 v are provided to maintain the center of the laser output 342 .
- the light receiving area 340 ′ although thinner is somewhat compensated by extending out the end of the photodiode.
- the submount 331 v includes a wider contact 343 v to which a bond wire 360 E 1 ′ from the semiconductor laser 332 can couple.
- a bond wire 360 C′′ is coupled between the post 204 A and the photodiode 330 v . Otherwise similar labeled elements are similar to those of FIG. 11A .
- the submount 331 v and photodiode 330 v are more readily manufacturable than making the notch 1100 in the submount portion 331 ′′′′ as is illustrated in FIG. 11A .
- the scribe lines along the edge of the submount 331 v and photodiode 330 v are straight and can be scribed readily on a semiconductor wafer.
- a separate thin submount 331 V (i.e., it's narrow) is provided from that of a separate photodiode 330 V ′ to maintain the center of the laser output 342 .
- the light receiving area 340 of the photodiode 330 V ′ remains the same as the original design.
- the submount 331 V ′ includes the wider contact 343 v to which the bond wire 360 E 1 ′ can couple to as previously described.
- a bond wire 360 C′′′ is coupled between the post 204 A and the photodiode 330 V ′. Otherwise similar labeled elements are similar to those of FIG. 11A .
- the submount 331 V ′ and photodiode 330 V ′ are more readily manufacturable than making the notch 1100 in the submount portion 331 ′′′′ as is illustrated in FIG. 11A .
- the scribe lines along the edge of the submount 331 v and photodiode 330 v are now straight and can be scribed readily on a semiconductor wafer.
- the light receiving area 340 of photodiode 330 V ′ needs no compensation in FIG. 12B .
- FIGS. 3A-3D illustrate the device package for the packaged semiconductor laser 300 as being a TO package with a four pin TO-header. It is understood that the number of pins and the header may vary depending upon the application and whether or not power monitoring is provided. To keep costs low, the header 314 can be a standard conventional header size dimensionally for a TO package.
- the packaged semiconductor laser may also be referred to herein as a packaged transmitter.
- the packaged transmitter 300 ′ includes a slanted window can 1312 , a header 1314 , and three leads 316 .
- the slanted window can 1312 includes a slant lid or angled top 1317 , a glass window 1318 , a window opening 1319 , and a can tab 1320 .
- the can tab 1320 mates with a rectangular slot 1322 in the header 1314 for proper alignment of the slant lid 1317 with the header 1317 .
- the glass window 1318 is hermetically sealed to the inside surface of the slanted window can 1312 . More particularly, the glass window 1318 is hermetically sealed to the inside surface of the slant lid 1317 of the slanted window can 1312 .
- the glass window 1318 has a circular shape and a diameter to cover over the window opening 1319 of the slant lid 1317 to seal out dust and dirt.
- the hermetic seal between the glass window and the slanted window can 1312 further prevents moisture from seeping into the packaged transmitter.
- the photodiode 1330 is attached to a header flange 1334 of the header 1314 .
- the photodiode 1330 has a submount portion.
- the VCSEL 1332 is attached to a top surface of the submount portion of the photodiode 1330 .
- the VCSEL 1332 is not mounted or attached to the header 1314 in order to keep short the wire bond lengths to the header posts.
- headers 314 , 314 ′, and 314 ′′, referenced here by header 1314 have a header diameter H D and a header thickness H TH .
- the header thickness H TH is a function of the header and the header flange. Adjustments in the header diameter H D and a header thickness H TH can vary the feedthrough impedance Z F .
- the header diameter H D and a header thickness H TH may be appropriately selected.
- the header and header flange are conductive and typically formed of a metal or alloy thereof. The type of metal or alloy may also influence the feedthrough impedance Z F such that this material selection may be taken into design consideration as well.
- the packaged semiconductor laser 300 ′ not only includes a semiconductor laser but provides a monitoring photodiode to allow for automatic power control (APC) of the output laser beam.
- the slanted window can or cap with its window is important in the provision of automatic power control (APC).
- FIG. 14A a magnified cut away side view of the packaged transmitter 300 or 300 ′ coupled to a block diagram of laser driving circuitry 1400 is illustrated.
- FIG. 14A illustrates the function of the slanted window can or cap.
- the slanted window can or cap supports the window 1318 on an angle to normal, above and aligned with the semiconductor laser 32 to receive a laser beam output from the semiconductor laser 1332 .
- the window 1318 in the slanted window can or cap functions as a beam splitter to proportionally split the incident laser beam 1460 it receives from the semiconductor laser 1332 .
- a deflected portion 1462 of the incident laser beam 1460 is deflected or reflected by the window 1318 to the photodiode 1330 .
- a non-deflected portion 1462 of the incident laser beam 1460 is transmitted through the window 1318 outside of the packaged laser transmitter 300 or 300 ′.
- the deflected portion 1462 is used to monitor the output power in the non-deflected portion 1462 as they are proportional to each other.
- the laser driver circuitry in response to monitoring the power in the deflected portion 1462 , adjusts the drive current provided to the semiconductor laser and the power of the laser beam 1460 .
- the packaged transmitter 300 or 300 ′ and laser driving circuitry 1450 are assembled together as part of a fiber optic transceiver module.
- the photodiode 1330 is attached to the header flange 1334 using a die attach epoxy 1350 .
- the VCSEL 1332 attaches to the submount portion of the photodiode 1330 using a die attach epoxy as well.
- the die attach epoxy 1350 is a conductor allowing an electrical contact to be made between the VCSEL 1332 and a first contact pad of the submount portion of the photodiode 1330 .
- the die attach epoxy 1350 allows an electrical contact to be made between the photodiode 1330 and the header flange 1334 .
- the slanted window can 1312 is coupled to the header 1314 by a weld seal 1352 .
- the glass window 1318 is attached to a back surface of the slant lid 1317 by the hermetic seal 1370 .
- the three leads 316 are separately labeled 316 A, 316 B, and 316 C in FIG. 14A to describe the electrical connections between the packaged transmitter 300 OR 300 ′ and the laser driving circuitry 1450 .
- Lead 316 C couples to ground at one end and the header flange 1334 at an opposite end.
- One of the bond wires couples between a first contact pad of the submount portion of the photodiode 1330 and the header flange 1334 .
- One of two terminals of the VCSEL 1332 electrically couples to the header flange 1334 .
- Lead 316 A couples to a terminal of the photodiode 1330 at one end and a monitoring input of the laser driving circuitry 1450 at another end.
- a photo current 1454 of the photodiode 1330 couples to the laser driving circuitry 1450 through lead 316 A.
- Lead 316 B is coupled to the output of the laser driving circuitry 1450 at one end and a second terminal of the VCSEL 1332 at an opposite end.
- the laser driving circuitry 1450 provides a laser drive current 1456 to the VCSEL 1332 to turn it on and off through lead 316 B.
- the laser driving circuitry 1450 receives a data input 1452 in order to modulate data onto an optical output of the packaged transmitter 300 or 300 ′.
- the VCSEL 1332 and photodiode 1330 can be powered up and be actively operating.
- the VCSEL 1332 generates a laser beam 1460 which is coupled into the glass window 1318 .
- the glass window 1318 acts as a beam splitter and reflects a portion of the power of the laser beam 1460 towards the photodiode 1330 as indicated by the reflected beam 1462 .
- the remaining power of the laser beam 1460 propagates through the glass window 1318 becoming the output beam 1464 of the packaged transmitter 300 or 300 ′.
- the power of the output beam 1464 is reduced from the power of the laser beam 1460 generated by the VCSEL 1332 by the amount of power in the reflected beam 1462 .
- the laser driving circuitry 1450 monitors the photo current 1450 of the photodiode 1330 in order to generate an appropriate laser drive current 1456 to automatically maintain a relatively constant power output in the output beam 1464 when the VCSEL 1332 is in an on state.
- FIG. 14B illustrates a magnified cross-sectional view of a portion of an embodiment of the window 1318 .
- the window includes a substrate material 1470 , such as glass, quartz, or plastic.
- the substrate material 1470 may have a first material layer 1472 and/or a second material layer 1474 on either side or both sides of the substrate material 1470 . That is, the window 1318 illustrated in FIG. 14B may include the substrate 1470 and the material layer 1472 , the substrate 1470 and the material layer 1474 , or the substrate 1470 and the materials layers 1472 and 1474 .
- Each of the material layers 1472 and/or 1474 may be formed of a thickness proportional to the wavelengths of the light that desire reflecting and/or transmission.
- the material layers 1472 and/or 1474 may be standard dielectric coating materials to allow transmission and deflection of light in one direction while reflecting light in another direction. That is, material layer 1472 in conjunction with the substrate layer 1470 and the material layer 1474 may provide beam splitting to light in a laser beam exiting from the semiconductor laser. The material layer 1474 may have an antireflection coating to keep light outside the package from entering into the package.
- the material layer 1472 and or the material layer 1474 provides reflection of an incoming light beam 1466 into the reflected output light beam 1466 ′.
- the material layer 1472 and or the material layer 1474 allow a portion of the light beam 1460 from the semiconductor laser to pass through the window 1318 as the output light beam 1464 . That is, the material layer 1472 and or the material layer 1474 allow the light beam 1460 from the semiconductor laser to be power split into a transmission portion 1464 and a deflection portion 1462 as illustrated.
- FIG. 14C illustrates a magnified cross-sectional view of a portion of another embodiment of the window, window 1318 ′.
- the window 1318 ′ includes the substrate material 1470 , such as glass, plastic quartz or other optical material.
- the window 1318 ′ further includes a plurality of layers on one or both sides of the substrate 1470 .
- a first plurality of layers may be alternating pairs of material layers 1472 a - 1472 n on an outer side of the substrate 1470 .
- a second plurality of layers may be alternating pairs of material layers 1474 a - 1474 n on an inner side the substrate material 1470 .
- the first plurality and the second plurality need not be alternating pairs of material layers but multiple layers. That is, the window 1318 ′ illustrated in FIG.
- the 14C may include the substrate 1470 and the first plurality of pairs of alternating material layers 1472 a - 1472 n , the substrate 1470 and the plurality of alternating pairs of material layers 1474 a - 1474 n , or the substrate 1470 and the plurality of alternating pairs of material layers 1472 a - 1472 n and 1474 a - 1474 n on each respective side of the substrate.
- Each of the plurality of material layers 1472 a - 1472 n and/or 1474 a - 1474 n may be formed of a thickness proportional to the wavelengths of the light that desire beam splitting.
- the alternating pairs of material layers 1472 a - 1472 n and/or 1474 a - 1474 n may be standard dielectric coating materials to allow beam splitting.
- the plurality of material layers 1472 a - 1472 n and/or the plurality of material layers 1474 a - 1474 n provide reflection for the incoming light beam 1466 into the reflected light beam 1466 ′.
- the plurality of alternating pairs of material layers 1472 a - 1472 n and or the plurality of alternating pairs of material layers 1474 a - 1474 n allow the light beam 1460 from the semiconductor laser to be power split into a transmission portion 1464 ′ and a deflection portion 1462 ′ as illustrated.
- FIG. 15A an exploded view of a Fiber Optic Transceiver Module 1500 is illustrated.
- FIGS. 15A-15B illustrates how a packaged semiconductor laser or transmitter 1510 is assembled into an optical block 1502 .
- the packaged semiconductor laser or transmitter 1510 is the packaged semiconductor lasers 300 or 300 ′ and their embodiments previously described.
- the Fiber optic module 1500 includes an optical block 1502 , a transmit printed circuit board (PCB) 1506 , a receive printed circuit board PCB 1508 , an optional internal shield 1509 , a packaged transmitter 1510 , a packaged receiver 1511 , a cover 1519 , an alignment plate 1551 , a nose receptacle 1552 , a nose shield 1553 , and a base 1555 .
- the alignment plate 1551 provides alignment between the optical block 1502 and a fiber optic cable plugged into the nose receptacle 1552 .
- the nose receptacle 1552 includes an optical fiber opening 1572 to receive an optical fiber connector and hold the optical fiber substantially fixed and aligned in place.
- the nose shield 1553 includes an opening 1574 for insertion over the nose receptacle 1552 and is conductive to reduce EMI.
- the packaged transmitter 1510 and packaged receiver 1511 are optoelectronic devices.
- An optoelectronic device is a device which can convert or transduce light or photons into an electrical signal or an electrical signal into light or photons.
- the packaged transmitter 1510 includes a vertical cavity surface emitting laser (VCSEL) 1590 that converts an electrical signal into light or photons.
- the packaged receiver 1511 is a packaged photodetector, including a photodetector 1592 that detects or receives light or photons and converts them into an electrical signal and is also preferably package in a TO can.
- the packaged transmitter 1510 is inserted into an opening 1564 in the optical block 1502 and epoxied thereto.
- the packaged receiver 1511 is inserted into an opening 1563 in optical block 1502 and epoxied thereto.
- the packaged transmitter 1510 has terminals 1560 to couple to through-holes of the transmit PCB 1506 .
- the terminals 1560 are soldered to make an electrical connection to the transmit PCB 1506 .
- the transmit PCB 1506 includes electrical components 1512 such as the laser driver circuitry and pins 1513 .
- the electrical components 1512 control the packaged transmitter 1510 and buffer the data signal received from a system through pins 1512 for transmission over an optical fiber.
- the packaged receiver 1511 has terminals 1561 to couple to through-holes of the receive PCB 1508 .
- the terminals 1561 are soldered to make an electrical connection to the receive PCB 1508 .
- the receive PCB 108 includes electrical components 1516 such as a receiver integrated circuit (transimpedance amplifier and post amplifier), and pins 1517 .
- the electrical components 1516 control the packaged receiver 1511 and buffer the data signal received from an optical fiber.
- the optical block 1502 includes lenses 1520 - 1523 and reflectors 1524 - 1525 .
- Lens 1523 is for collimating the light or photons diverging from the packaged transmitter 1510 .
- Lens 1522 is for focussing the collimated light or photons into an optical fiber.
- Lens 1520 is for collimating the light or photons diverging out from the end of an optical fiber into the optical block 1502 .
- Lens 1521 is for focusing the collimated light or photons into the packaged receiver 1511 .
- Reflectors 1524 - 1525 are forty five degree angle facets formed in the optical block 1502 to provide total internal reflection and redirect the light rays between the optical fibers and the optoelectronic devices.
- the facets may be coated with a reflective surface or mirror surface to reflect light or photons off the reflective coated surface or facets having an optical grating surface to reflect photons.
- none of the elements of the optical block 1502 are used to redirect a light beam or ray back into the packaged transmitter 1510 . That is, the lens 1523 , reflector 1525 , lens 1522 associated with the packaged transmitter 1510 , are used to couple light forward into an optical fiber and not to reflect light back into the packaged transmitter 1510 .
- the packaged transmitter 1510 includes a semiconductor laser such as a vertical cavity surface emitting laser 1590 for generation of light or photons in response to electrical signals from the transmit PCB 1506 .
- a semiconductor laser such as a vertical cavity surface emitting laser 1590 for generation of light or photons in response to electrical signals from the transmit PCB 1506 .
- Light or photons emitted by the packaged transmitter 1510 are coupled into lens 1523 and collimated onto the reflector 1525 at an incident angle I 1 (angle with the perpendicular to reflector 1525 surface) of substantially forty five degrees.
- Reflector 1525 reflects the incident light or photons on a refraction angle R 1 (angle with the perpendicular to reflector 1525 surface) equivalent to incident angle I 1 of substantially forty five degrees.
- the reflected light or photons travel perpendicular to the incident light or photons towards the lens 1522 .
- Lens 1522 focuses the light or photons from the packaged transmitter 1510 into an aligned optical fiber through an optical port 1567 in the alignment plate 1551 .
- light or photons coupled or launched into an optical fiber, defining a first optical axis are substantially perpendicular to the light or photons emitted and incident upon lens 1523 from the packaged transmitter 1510 .
- FIGS. 16A-16B illustrate how a packaged semiconductor laser or transmitter 1620 is assembled into an SC fiber optic plug or connector 1650 A.
- the packaged semiconductor laser or transmitter 1620 is the packaged semiconductor lasers 300 or 300 ′ and their embodiments previously described.
- the fiber-optic module 1600 includes a cover 1601 , a module chassis frame 1602 , a printed circuit board (PCB) 1610 , a packaged transmitter 1620 , a packaged receiver 1621 , a pair of shielding collars 1622 A and 1622 B, a pair of SC fiber optic plugs or connectors 1650 A and 1650 B, and a U-Plate 1624 .
- the optical, electrical and opto-electronic components of the fiber-optic module 1600 are assembled into the module chassis frame 1602 and the cover 1601 is then fitted to the module chassis frame 1602 .
- the module chassis frame 1602 includes optical connector receptacles 1603 (including openings 1604 ), and a base 1606 .
- the openings 1604 are SC optical connector openings for a duplex SC optical connection.
- the optical connector openings 1603 are separated by a slot 1638 .
- the packaged transmitter 1620 may include the vertical cavity surface emitting laser (VCSEL) for transmitting optical signals.
- the packaged receiver 1621 includes a photodiode for receiving optical signals.
- Each package of the package transmitter 1620 and the packaged receiver 1621 may be a standard TO package.
- Each of the packaged transmitter 1620 and receiver 1621 have one or more terminals 1619 which couple to the edge traces 1614 ( 1614 T and 1614 B) on each side of the printed circuit board 1610 .
- the printed circuit board 1610 includes one or more PCB signal pins 1612 , edge traces 1614 on each side for mounting the packaged transmitter 1620 and the packaged receiver 1621 , and one or more integrated circuits 1616 for processing signals between the signal pins 1612 and the packaged transmitter 1620 and the packaged receiver 1621 .
- the one or more integrated circuits includes the laser driver circuitry previously discussed.
- the SC fiber optic plugs or connectors 1650 A and 1650 B include a lens 1651 A and 1651 B mounted inside ports 1623 A and 1623 B, respectively.
- the lenses 1651 A and 1651 B are between the fiber ferrules and the TO-cans of the packaged transmitter 1620 and packaged receiver 1621 respectively.
- Each of the SC connectors 1650 A and 1650 B further includes a pair of snap lock clips 1652 each having a retaining protrusion 1653 , ferrule barrels 1654 , support struts 1656 in a front portion.
- Each of the SC connectors 1650 A and 1650 B further includes circular recesses 1657 between each of the headers 1623 A and 1623 B and their respective flanges 1655 in a rear portion. Each of the circular recesses 1657 mates with the U-shaped openings 1627 of the U-plate 1624 .
- the packaged transmitter 1620 is mounted inside the transmitter port 1623 A of the SC fiber optic plug or connector 1650 A to form a Transmitter Optical Subassembly.
- the shielding collar 1622 A is slid over the port 1623 A.
- the terminals 1619 of the packaged transmitter 1620 are then soldered onto the PCB 1610 .
- the packaged receiver 1621 is mounted inside the receiver port 1623 B of the SC fiber optic plug or connector 1650 B to form a Receiver Optical Subassembly.
- the shielding collar 1622 B is slid over the port 1623 B.
- the terminals 1619 of the packaged receiver 1621 are then soldered onto the PCB 1610 .
- the optical, electro-optical, and the electronic components are assembled into the module chassis frame 1602 before the cover 1601 encloses it.
- the front portion of the SC connectors 1650 A and 1650 B are inserted into the openings 1603 in the nose of the module chassis frame 1602 .
- the U-plate 1624 is coupled to the module chassis frame so that its U-openings 1627 fit into the circular recesses 1657 of each respective connector 1650 A and 1650 B.
- the U-plate 1624 holds the subassembly of the optical and electrical components coupled into the module chassis frame 1602 .
- FIG. 16B a cross-sectional view of the SC optical plugs or connectors 1650 A and 1650 B is illustrated assembled in the fiber optic module 1600 .
- the package transmitter 1620 is mounted inside the transmitter port 1623 A of the SC fiber optic plug or connector 1650 A.
- the shielding collar 1622 A is around the port 1623 A.
- the terminals 1619 of the packaged transmitter 1620 are soldered onto the PCB 1610 .
- the packaged receiver 1621 is mounted inside the receiver port 1623 B of the SC fiber optic plug or connector 1650 B.
- the shielding collar 1622 B is around the port 1623 B.
- the terminals 1619 of the packaged receiver 1621 are soldered onto the PCB 1610 .
- the SC fiber optic plugs or connectors 1650 A and 1650 B include the lens 1651 A and the lens 1651 B mounted inside ports 1623 A and 1623 B, respectively.
- the lens 1651 A is between the fiber ferrule 1654 and the packaged transmitter 1620 .
- the lens 1651 B is between the fiber ferrule 1654 and the packaged receiver 1621 .
- the packaged transmitter 1620 includes the vertical cavity surface emitting laser (VCSEL) for generation of light or photons in response to electrical signals from the PCB 1610 .
- VCSEL vertical cavity surface emitting laser
- Light or photons emitted by the packaged transmitter 1620 are coupled into lens 1651 A, collimated and focused into an aligned optical fiber plugged into the SC fiber optic plug 1650 A.
- light or photons from the packaged transmitter 1620 are coupled or launched into an optical fiber through the lens 1651 A.
- None of the elements of the SC fiber optic plug or connector 1650 A are used to redirect a light beam or ray back into the packaged transmitter 1620 . That is, the lens 1651 A associated with the packaged transmitter 1620 , is used to couple light forward into an optical fiber and not to reflect light back into the packaged transmitter 1620 .
- a high-bandwidth TO-header based packaging for VCSEL (2) A packaging scheme to arrange a VCSEL and a PCB circuit on a TO-header; (3) Impedance control of the feedthrough of the pins of the TO-header is, according to the resistance of the VCSEL; (4) An Impedance-controlled circuit as a medium for shortening of wire bonds to reduce the inductance of terminals of the device package; (5) The impedance-controlled circuit can have different impedance to match the resistance of different VCSELs used; (6) Thick wire bond wire (or ribbon wire) for reducing inductance introduced by wire bonding; (7) Packaging scheme for a VCSEL on a submount to provide a short bond wire length; (8) A submount to provide mechanical support to the VCSEL, and including a photodetector to generate a monitor current; (9) Electrical vias in the submount for shorting a ground contact of the VCSEL to the top of the header as
Abstract
Semiconductor packaging methods, systems and apparatus for semiconductor lasers to achieve high modulation bandwidth. Systems, methods and apparatus for minimizing the inductance of wire bond interconnects and impedance matching in a semiconductor laser package. Systems, methods and apparatus for monitoring a photocurrent in order to provide automatic power control (APC) of a semiconductor laser.
Description
- This U.S. Non-Provisional Patent Application claims the benefit of U.S. Provisional Patent Application No. 60/403,998 entitled “SEMICONDUCTOR LASER PACKAGING FOR HIGH MODULATION BANDWIDTH”, filed Aug. 16, 2002 by Michael Zhou et al.
- The invention relates generally to the field of optoelectronic device packaging. Particularly, the invention relates to semiconductor laser packaging.
- The features of the invention will become apparent from the following detailed description of the invention in which:
-
FIG. 1 is a block diagram of a typical optical data link. -
FIG. 2 is a functional block diagram illustrating the impedances around a packaged semiconductor laser including the impedance controlled circuit. -
FIGS. 3A-3D are magnified views of an embodiment of a packaged semiconductor laser including the impedance controlled circuit. -
FIG. 4A is a magnified cross-sectional side view of an alternate embodiment of the packaged semiconductor laser including the impedance controlled circuit. -
FIGS. 4B-4C are magnified views of another alternate embodiment of the packaged semiconductor laser including the impedance controlled circuit. -
FIGS. 5A-5B are magnified views of the impedance controlled circuit. -
FIGS. 6A-6B are magnified perspective views of a pair of different bond wires to further reduce impedance. -
FIGS. 7A-7C are magnified views of a dielectric feedthrough to provide a nominal input impedance at the pin. -
FIG. 8A is an exploded view of a semiconductor laser package without the can lid to illustrate the assembly of the pin and feedthrough into the header. -
FIG. 8B is a magnified cross-sectional side view of an assembled pin and feedthrough in the header. -
FIG. 9 is a bottom view of the packaged semiconductor laser having standard pin spacing. -
FIG. 10A is a magnified top view of a first alternate header with a first altered pin spacing for another embodiment of the packaged semiconductor laser. -
FIG. 10B is a bottom view of the packaged semiconductor laser having the first altered pin spacing ofFIG. 10A . -
FIG. 11A is a magnified top view of a second alternate header with a second altered pin spacing and a first submount modified thereto for another embodiment of the packaged semiconductor laser. -
FIG. 11B is a bottom view of the packaged semiconductor laser having the second altered pin spacing ofFIG. 11A . -
FIG. 12A is a magnified top view of the second alternate header with the second altered pin spacing and a photodiode and a second submount modified thereto for another embodiment of the packaged semiconductor laser. -
FIG. 12B is a magnified top view of the second alternate header with the second altered pin spacing and a third submount modified thereto separate and apart from the photodiode for another embodiment of the packaged semiconductor laser. -
FIGS. 13A-13B illustrate an alternate thin outline package including an alternate header and variable dimensions related thereto. -
FIG. 14A is a block and ray diagram illustration of automatic power control of a surface emitting semiconductor laser and in response to power monitoring by a photodiode. -
FIGS. 14B-14C illustrate alternate embodiments of the material layers of the window of the slanted can or cap. -
FIG. 15A is an exploded view of an first exemplary fiber optic module including an optical block to illustrate a higher order assembly of the packaged semiconductor laser. -
FIG. 15B is a cutaway side view of the packaged semiconductor laser mechanically coupled to the optical block illustrated inFIG. 15A . -
FIG. 16A is an exploded view of a second exemplary fiber optic module including a fiber optic plug with a lens to illustrate a higher order assembly of the packaged semiconductor laser. -
FIG. 16B is a cutaway side view of the packaged semiconductor laser mechanically coupled to the fiber optic plug including a lens as illustrated inFIG. 16A . - The invention is summarized by the claims that follow below.
- In the following detailed description of the invention, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, the invention may be practiced without these specific details. In other instances well known methods, procedures, components, and circuits have not been described in detail so as not to unnecessarily obscure aspects of the invention.
- In recent years there has been an increase in applications for ten gigabit per second (Gbps) optical communication systems. High-speed and low cost laser modules are in great demand. In ten Gbps applications, the semiconductor laser is typically packaged in a Mini-DIL package which is usually very expensive. The Mini-DIL package for a semiconductor laser is difficult to use in many applications where packaging size constraints, power consumption, and/or a high yield process are desirable.
- In an embodiment of the invention a high-performance, yet low-cost packaging scheme for 10 gigabit per second (Gbps) vertical cavity surface emitting lasers (VCSEL) is disclosed. The semiconductor laser is packaged in a thin outline (TO) based package with added features for high-speed performance and laser power monitoring for automatic power control (APC). The packaged semiconductor laser may be incorporated into an optical transceiver or fiber optic module of an optical data link or an optical communication system.
- Referring now to
FIG. 1 , a typical optical data link is illustrated. An optical data link includes anoptical transceiver 100A, anoptical transceiver 100B, and at least onefiber optic cable 102. Each of theoptical transceivers optical fiber 102. The elements of eachoptical transceivers optical fiber 102 includes afirst plug 104A and asecond plug 104B. - The typical block functional elements of the
optical transceiver 100A includes a nose or fiberoptic receptacle 110, anoptical block 112,optical electronics 114, transmit and receive electronics 116, and pins, terminals, pads, orconnectors 118. - The nose or fiber
optic receptacle 110 receives thefiber optic plug 104A of the at least oneoptical fiber 102. The nose mechanically couples to theoptical fiber 102. The nose may have an opening to receive various types of fiber optic plugs including simplex and duplex type plugs. The fiberoptical receptacle 110 holds theplug 104A in alignment with the optical block. - The
optical transceiver 100A may couple to ahost system 106. In order to do so thehost system 106 may include poles, terminals, pads, orconnectors 120 to couple to the pins, terminals, pads, orconnectors 118 respectfully of theoptical transceivers 100A. The pins, terminals, pads, orconnectors 118 of theoptical transceiver 100A is for coupling to thehost system 106. - The
optical block 112 is for coupling light between theoptical electronics 114 and theoptical fiber 102. Theoptical block 112 may include one or more lenses or light bending elements to couple light between theoptical fiber 102 and the packagedoptoelectronic components 114. - The packaged
optoelectronic components 114 may transduce between electrical signals and optical signals. The packagedoptoelectronic components 114 may include a packaged semiconductor laser, a packaged semiconductor detector, or both. - The transmit and receive electronics 116 appropriately controls the packaged
optoelectronic components 114 to generate lights signals or receive light signals as well as electrical signals at the pins, terminals, pads, orconnectors 118. - In packaging a semiconductor laser, a thin outline (TO) based package has been used for two and one half Gbps or lower data-rate lasers in the various telecommunication and data-communication applications in the past few years. Typically, a VCSEL die is mounted in the center of the TO header, with its electrical connection directly on a header's posts. The length of the wire bond in this case typically ranges from one and one-half millimeters (mm) to two and one-half mm or longer. This results in a critical electrical path which is long, and therefore has a relatively large inductance. A VCSEL packaged in this manner may typically have a modulation bandwidth of about two to four gigaHertz (GHz). In some cases, five to seven GHz may be achieved, depending on the arrangement of the wire bonding. However, the current TO structure and wire bonding scheme limits performance below ten Gbps performance.
- In order to improve performance to ten Gbps, the packaged semiconductor device can include an impedance-controlled circuit is combined with the design and selection of the dimensions and materials of the package along with the position and electrical connections to provide impedance matching in a number of embodiments. In other embodiments, the dimensions and materials of the package may be designed and selected to provide impedance matching along with the positioning and electrical connections made to the optoelectronic device in the package without the impedance controlled circuit.
- Referring now to
FIG. 2 , a block diagram of an application of the impedance controlledcircuit 202 is illustrated. The impedance-controlledcircuit 202 is coupled between the semiconductor laser 200 (such as a VCSEL) and the TO-header post 204. The impedance-controlledcircuit 202 functions to reduce impedance in the ordinary interconnect to the semiconductor laser when a standard package is used. The Minimizedinterconnections circuit 202 and thesemiconductor laser 200 and TOheader post 204 are formed respectively with reduced impedances. - To avoid transmission line reflections, the impedances Z1 and Z2 of impedance controlled
circuit 202 are impedance matched to the impedance ZL ofsemiconductor laser 200 and the feedthrough impedance ZF as seen at theTO header post 204 orpin 205, respectively. In a preferred embodiment, the impedances Z1 and Z2 of the impedance controlledcircuit 202 are equal to each other and to the impedance ZL Ofsemiconductor laser 200 and the feedthrough impedance ZF. For example, a nominal impedance for thesemiconductor laser 200 at a given frequency or frequency range is fifty ohms. The design of the TO package is slightly adjusted so that the nominal feedthrough impedance ZF matches the nominal impedance of thesemiconductor laser 200. Thus in the example, ZF is also fifty ohms at the given frequency or frequency range. The design of the impedance controlledcircuit 202 provides nominal impedances for Z1 and Z2 which are the same to match that of thesemiconductor laser 200. Thus in the example, Z1 and Z2 which are equal are also fifty ohms at the given frequency or frequency range. - In other embodiments, the impedance-controlled
circuit 202 may additionally be used to compensates for what otherwise might be a slight mismatch between the impedances of the TO-header post and the semiconductor laser including the interconnect there-between and thepin 205. In which case, Z1 and Z2 may be unequal or equal at the nominal frequency, but provide compensation at other frequencies. The impedance-controlledcircuit 202 may compensate for resistance, inductance, and capacitance. - Referring now to
FIG. 3A , a perspective view of a packagedsemiconductor laser 300 is illustrated. The packaged semiconductor laser may also be referred to herein as a packaged transmitter because they are used in communication systems to transmit data signals using light signals. - The packaged
semiconductor laser 300 includes a slanted window can or cap 312, aheader 314, and pins or leads 316 of a device package. In a preferred embodiment, the device package is a thin outline (TO) type of device package and the slanted window can or cap 312 is a slanted window TO can or cap and theheader 314 is a TO header. Theheader 314 generally provides mechanical support and electrical connections to one or more pins. The slanted window can or cap 312 generally provides a hermetic seal to theheader 314 to enclose a device, allows a portion of laser light to pass out through a window and from the package, and reflects a portion of the laser light back to aphotodetector 330 for power monitoring and automatic power control of the semiconductor laser. That is, the window of the slanted window can is partially transparent and partially reflective to the laser beam emitted from the semiconductor laser. The reflected light on the photodetector generates a monitor current for control of the output power from the semiconductor laser. - The slanted window can 312 includes a
lip 313, a slant lid or angled top 317, aglass window 318, and awindow opening 319 as shown and illustrated. Thelip 313 of the slanted window can 312 is for sealing to a surface of theheader 314. Theglass window 318 allows a portion of the laser beam to pass through it. Thewindow opening 319 allows the portion of the laser beam to exit out from thepackage 300 into space or into a fiber optic cable or other optical transmission media. The slanted window can 312 may further include a can tab that mates with a slot in theheader 314 for proper alignment of theslant lid 317 and the slant window can 312 with theheader 314. A can tab and slot are described below and illustrated in other Figures herein. - Referring now to
FIG. 3B , a cut away side view of the packagedsemiconductor laser 300 is illustrated. Theglass window 318 is hermetically sealed to the inside surface of the slanted window can 312. More particularly, theglass window 318 is hermetically sealed to the inside surface of theslant lid 317 of the slanted window can 312. Theglass window 318 may have a circular shape and a diameter to cover over thewindow opening 319 of theslant lid 317 to seal out dust and dirt. The hermetic seal between theglass window 318 and the slanted window can 312 further prevents moisture from seeping inside into the packaged semiconductor laser. - Inside the packaged
semiconductor laser 300 is a semiconductor photodiode orphotodetector 330, asemiconductor laser 332 such as a vertical cavity surface emitting laser (VCSEL), and the impedance controlledcircuit 202. In a preferred embodiment, the photodiode is a PIN type of photodiode. Thephotodiode 330 and the impedance controlledcircuit 202 are attached to a surface of aheader flange 334 of theheader 314. The impedance controlledcircuit 202 couples to aheader post 204 of one of thepins 316 which extends above the header. The impedance controlledcircuit 202 further couples to thesemiconductor laser 332. - The
photodiode 330 has a submount portion 331 (better illustrated inFIGS. 3C and 3D ). Thesemiconductor laser 332 is attached to a top surface of thesubmount portion 331 of thephotodiode 330. Thesubmount portion 331 of thephotodiode 330 may include vias to electrically couple between theheader flange 334 and a substrate surface of theVCSEL 332. In another embodiment, thesubmount portion 331 may be a submount separate and apart from thephotodiode 330. - Referring now to
FIG. 3C , a perspective view of the packagedsemiconductor laser 300 without the slanted window can 312 and bond wire interconnects is illustrated. As discussed previously, thesemiconductor laser 332 is attached to a top surface of thesubmount portion 331 of thephotodiode 330. Thesubmount portion 331 of thephotodetector 330 locates the semiconductor laser die 332 in position within the package in x, y and z coordinates. - To emit light or photons transduced from an electrical signal or electrons, the
semiconductor laser 332 includes asurface emitting area 342 and an active region (not shown) formed of one or more quantum well structures. - For transducing light or photons into an electrical signal or electrons, the
photodiode 330 includes alight detection area 340 opposite thesubmount portion 331. The light detecting area 340 (acting as a photodetector) is a monitoring photodetector to detect and monitor the output power of thesemiconductor laser 332. -
FIG. 3D is a magnified top view of an embodiment of the packagedsemiconductor laser 300 without the slanted window can 312 assembled thereto. InFIG. 3D , bond wire interconnects (generally referred to as 360) or bond wires are illustrated forming electrical connections between elements of the packagedsemiconductor laser 300. - Referring now to
FIGS. 3C and 3D , the impedance-controlledcircuit 202 is located between thesemiconductor laser 332 and the TO-header post 204B. The impedance-controlledcircuit 202 includes at least one impedance-control line 370 fabricated on top of a printedcircuit board 372. - As illustrated in
FIG. 3D , one end of the at least one impedance control line 370 (i.e., a transmission line) of the impedance controlledcircuit 202 will be wire-bonded to the TO-header post 204B to receive a driving current for thesemiconductor laser 332 from thepin 316B. An opposite end of the at least one impedance control line 370 (i.e., a transmission line) of the impedance controlledcircuit 202 will be wire-bonded to the semiconductor laser die 332 to provide the drive current thereto. - A
wire bond 360A couples to theheader post 204B at one end and the at least oneimpedance control line 370 at an opposite end. Awire bond 360B couples to a bonding pad of thesemiconductor laser 332 at one end and the at least oneimpedance control line 370 at an opposite end. Awire bond 360C couples to a bonding pad of thesemiconductor photodetector 330 at one end and theheader post 204A at an opposite end. - In one embodiment, the
submount 331 may include alarge bonding pad 343 to which multiple wire bonds may be coupled. InFIG. 3D , wire bonds 360D1 and 360D2 couple to theheader flange 334 at one end and thebonding pad 343 at an opposite end. Wire bonds 360E1 and 360E2 couple to a pair of pads of thesemiconductor laser 332 at one end and thebonding pad 343 at an opposite end. Theheader flange 334 is coupled to at least one of thepins 316. Typically the header flange is grounded to a source of ground or a low level voltage supply. - Each of the
wire bonds 360 has an impedance associated with it. Typically the impedance of a bond wire is mostly inductance. The resistance in the bond wires are usually negligible but for the case of high currents. The shorter the length of the bond wire the less inductance and resistance there is in the bond wire. The larger the diameter of the bond wire, the less inductance and resistance there is associated with it. Coupling two bond wires in parallel together, such as bond wires 360D1 and 360D2 for example, lower the resistance and inductance of the overall connection between two points because the resistance and inductance of each are placed in parallel. - As illustrated in
FIGS. 3C and 3D , the positioning of thesemiconductor laser 332, the impedance controlledcircuit 202, and theheader post 204B are such to minimize the lengths of thebond wires control line 370. The impedance controlledcircuit 202 is die attached onto a top surface of theheader flange 334 relatively close to theheader post 204B to minimize the length ofbond wire 360A. The submount 331 (i.e. photodetector 330 including submount portion 331) is die attached onto a top surface of theheader flange 334 relatively close to the impedance controlledcircuit 202 and the semiconductor die 332 is die-attached onto a top surface of thesubmount 331 and located next to an edge thereof closest to the impedance controlledcircuit 202 to minimize the length ofbond wire 360A. - The heights relative to the
header flange 334 of the top surface of thesemiconductor laser 332 and the top surface of the at least onecontrol line 370 to whichwire bond 360B is formed is substantially equal to further minimize the length of thebond wire 360B. The heights relative to theheader flange 334 of the top surface of theheader post 204B and the top surface of the at least onecontrol line 370 to whichwire bond 360A is formed is substantially equal to further minimize the length of thebond wire 360A. - In other words, one contact point of the at least one
control line 370 is made as close as possible to theheader post 204B and another contact point of the at least onecontrol line 370 is made as close as possible to a wire bond pad on thesemiconductor laser 332. Generally, the elements are placed so that the at least oneimpedance control line 370 is made as close as possible to theheader post 204B and thesemiconductor laser 332 so that the bond wires are kept as short as possible. - To further reduce inductance in the bond wires, a thicker bond wire can be used as the
bond wires 360 as is discussed further below. Furthermore, extra wire bonding may be used to reduce inductance when added in parallel and in the case larger currents are expected. For example, extra bond wires 360D1 and 360D2 are used to couple thecontact 331 to theheader flange 334 and couple large currents to ground. In these cases, the length of the wire bonding is greatly reduced to minimize inductance introduced by the bond wire without any impedance matching provided by theimpedance control circuit 202. - Referring now to
FIG. 4A , a magnified cross sectional right side view of an another embodiment is illustrated.FIG. 4A illustrates asubmount 331′, asemiconductor laser 332′, and the impedance controlled circuit. In order to further reduce inductive coupling to the semiconductor laser, thesubmount 331′ has one ormore vias 402 to electrically connect a top large bonding pad orsurface contact area 343′ to a bottomsurface contact area 406 of the submount. The bottomsurface contact area 406 is die attached to theheader flange 334 using a conductive epoxy to mechanically and electrically couple the bottomsurface contact area 406 to a top surface of theheader flange 334. The impedance controlledcircuit 202 includes aground plane 470 which is also die attached to theheader flange 334 using a conductive epoxy to mechanically and electrically couple thereto. - A bottom surface of the
semiconductor laser 332′ in this case hasbottom contacts 414. Thebottom contacts 414 of thesemiconductor laser 332′ couple to thesurface contact area 343′ of thesubmount 331 and electrically connect through thevias 402 to theheader flange 334. Optional vias 412 in thesemiconductor laser 332′ may be used to route an upper connection to thebottom contacts 414 in order to make such a connection. This embodiment eliminates the wire bonds 360D1, 360D2, 360E1 and 360E2 illustrated inFIG. 3D to further reduce inductance in the connections to thesemiconductor laser 332. -
FIG. 4A also illustrates how the submounts described herein elevate and mechanically support the semiconductor laser die above the header flange at a level near the top of the header posts. Thus being at the same height, wire bonds may be made between the semiconductor laser die and the top of the header posts with minimal lengths. - Referring now to
FIG. 4B , a magnified top view of yet another embodiment for the packaged semiconductor laser is illustrated.FIG. 4B illustrates a top view of asubmount 331″ of aphotodetector 330″, thesemiconductor laser 332′, the impedance controlledcircuit 202 and aconductive block 422. - The wire bonds 360E1 and 360E2 illustrated in
FIG. 3D have been eliminated by using the optional vias 412 in thesemiconductor laser 332′. Thebottom contact 414 of thesemiconductor laser 332′ couples to the large bonding pad orsurface contact 343″ of thesubmount 331″. - The wire bonds 360D1, and 360D2 illustrated in
FIG. 3D have been eliminated by conductively epoxying a top surface of theconductive block 422 to thesurface contact 343″ of thesubmount 331″ and a bottom surface of theconductive block 422 to theheader flange 334. - The
conductive block 422 is formed out of a conductive material such as metal, an alloy, or other conductive material. Theconductive block 422 may be rectangularly shaped as illustrated, cylindrically shaped, or take on another shape so that theconductive block 422 has atop surface 423 to which a conductive epoxy could adhere and form an electrical connection thereto. - A
conductive epoxy 444 electrically couples thetop surface 423 of theconductive block 422 to thesurface contact 343″. In order to do so, an edge of thesurface contact 343″ extends out to substantially meet an edge of thesubmount portion 331″ of thephotodetector 330″ and the height of theconductive block 422 is substantially similar to the height of thesubmount portion 331″. In other words, theconductive block 422 is approximately level with thesurface contact 343″. Theconductive epoxy 444 electrically couples to thesurface contact 343″ at the extended edge of thesurface contact 343″. - Referring now to
FIG. 4C , a magnified cross-sectional front side view of the embodiment ofFIG. 4B is illustrated. Thephotodetector 330″ and theconductive block 422 are die attached to theheader flange 334 as close as possible to each other leaving only asmall gap 448. Abottom surface 424 of theconductive block 422 is epoxied using theconductive epoxy 444 to theheader flange 334. This mechanically and electrically couples theconductive block 422 to theheader flange 334. Abottom contact 406′ of thephotodetector 330″ may also be conductively epoxied to theheader flange 334. - When mounted to the
header flange 334, theconductive block 422 is approximately level with thesurface contact 343″ of thesubmount portion 331″ of thephotodetector 330′ as is illustrated. A strip ofconductive epoxy 444 is poured onto both thetop surface 423 of theconductive block 422 and thesurface contact 343″ of thesubmount 331″ across thegap 448. The conductive epoxy effectively provides a bridge connection across thegap 448. As previously discussed, theconductive epoxy 444 electrically couples to thesurface contact 343″ at the extended edge of thesurface contact 343″. The width of theconductive epoxy 444 along the edge of thesurface contact 343″ may be adjusted to vary the impedance of the connection made. A wider strip of conductive epoxy further reduces the impedance of the bridge connection over thegap 448. - The
semiconductor laser 332′ is shown illustrated in the embodiment ofFIGS. 4B-4C using abottom connection 414 and possibly an optional via 402 if necessary. However, thesemiconductor laser 312 with top bonding pads and bond wires 360E1 and 360E2 as illustrated inFIG. 3D may be used to couple the laser to thesurface contact 343″. - Referring now to
FIGS. 5A and 5B , magnified views of the impedance controlledcircuit 202 are illustrated.FIG. 5A illustrates a top magnified view of the impedance-controlledcircuit 202.FIG. 5B illustrates a side magnified view of the impedance controlledcircuit 202. As discussed previously, the at least oneimpedance control line 370 is formed on a top surface of the printedcircuit board 372. The printedcircuit board 372 of the impedance-controlledcircuit 202 includes aground plane 470 having a surface which is die attached by aconductive epoxy 502 to a top surface of theheader flange 334. Theheader flange 334 electrically couples to theground plane 470. The printedcircuit board 372 is a dielectric and depending upon its selection may have different dielectric constants. The ground plane is for the at least one impedance-control line 370. - The at least one
impedance control line 370 may be formed using microstrip line or transmission line techniques. In either case, theimpedance control line 370 is a wave guide to the signal that propagates across it. Theimpedance control line 370 may include circuit element equivalents formed using microstrip line techniques or transmission line techniques. The at least oneimpedance control line 370 may generally be considered to have a length L, a width W, and a thickness T. Variations in width, length, and thickness of the least onecontrol line 370 may occur from one end to another in order to achieve a desired impedance effect. Additionally, a plurality ofimpedance control lines 370 may be coupled together in different ways to achieve desired impedances in the impedance controlledcircuit 202. Furthermore, other discreet components may be coupled to the printed circuit board 373 to provide impedance compensation. The discreet components may be chip resistors, chip capacitors, or chip inductors. - The printed
circuit board 372 may be a laminate of material layers of a standard laminate grade (e.g., Rogers FR-xx, G-xx, and GPO-.xx) or a solid material such as ceramic. Pairs of the material layers for the printedcircuit board 372 may be paper/phenolic, paper/epoxy, glass/epoxy, glass/phenolic, glass/melamine, glass/polyester, and teflon fiberglass. The material layers establish an associated dielectric constant for the printed circuit board and a thickness which effects the impedance of the at least oneimpedance control line 370. - The at least one
impedance control line 370 is formed of a conductive material, such as a metal, and has dimensions of a length, a width, and a thickness. These dimensions may also be a factor in the impedance of the at least oneimpedance control line 370. The type of conductive material may also be a factor in the impedance of the at least oneimpedance control line 370. The conductive material may be a metal such as gold, copper, silver, titanium, and aluminum, an alloy thereof, or another conductive element such as silicon, germanium, or carbon. The signal wavelength in free space (i.e., ) which is a function of the signal frequency is also a factor to consider in designing the impedance of the at least oneimpedance control line 370. The length dimension of the at least oneimpedance control line 370 is often proportional to a fraction of the wavelength of the signal in free space. - The impedance controlled
circuit 202 provides a nominal impedance at a given frequency or over an average frequency range. For example, the nominal impedance of theimpedance control circuit 202 is fifty ohms at ten gigaHertz (i.e., ten Gbps) in a preferred embodiment. It is desirable that the nominal impedance of the impedance controlledcircuit 202; thefeedthrough 345B and/orfeedthroughs 345A-345B; and thesemiconductor laser 332 match. - Referring now to
FIGS. 6A and 6B , perspective views of different types of bond wires are illustrated. InFIG. 6A , a standard circularcylindrical bond wire 360 is illustrated. The diameter of the circular cross section of thebond wire 360 is d. The diameter d is typically twenty-five microns wide. The inductance and impedance of thebond wire 360 may be reduced by using a larger diameter bond wire where d is greater than thirty microns for example. The diameter d may be from thirty to one hundred fifty microns or more for example to reduce the induction and impedance therein. To accommodate the largerdiameter bond wire 360, the dimensions of the bonding pads of the devices may need to be increased accordingly. - Reduction in impedance in the bond wires may also be obtained by using a “ribbon bond wire” 360′. The
ribbon bind wire 360′ is a rectangular cylindrical bond wire. The rectangular cross section of theribbon bond wire 360′ has dimensions of a height h and a width w. The width w of theribbon bond wire 360′ is significantly greater than the height h in order to reduce the inductance and impedance of the bond wire. Assume for example that the height h may be the same as the standard diameter of the circular bond wire, twenty-five microns. The width w of theribbon bond wire 360′ is significantly greater than the height h, such as a multiple or four or five times the dimension of the height h for example. In the case that the height is twenty five microns, the width w of theribbon bond wire 360′ may be on the order of one-hundred to one-hundred-twenty-five microns. To accommodate the larger dimensions of theribbon bond wire 360′, the dimensions of the bonding pads of the devices may need to be increased accordingly. In which case, theribbon bond wire 360′ may replace one or more of thebond wires 360 illustrated in the Figures (e.g.,bond wires 360A-360E2 illustrated inFIG. 3D ). - Referring now to
FIGS. 7A-7C magnified views of afeedthrough 345 used for at least feedthrough 345B are illustrated.Feedthrough 345 referred to herein generally representsfeedthroughs Feedthrough 345 as illustrated in a magnified top view ofFIG. 7A is shaped similar to a hollow circular cylinder with a thickness th. Thefeedthrough 345 has a radius R1 which is in the inner radius of the hollow cylinder and a radius R2 which is the outer radius of the hollow cylinder. The thickness of thefeedthrough 345 is the difference between R2 and R1 which is given by the equation of th=R2−R1. - The empty
solid cylinder 701 of radius R1 is where a portion of thepin 316 would otherwise fill. The radius R1 may be considered to be substantially equal to the radius of the pin. The radius R2 conforms to a solid cylinder that fills a cylindrical opening in theheader 314. - Referring now to
FIG. 7B , a magnified cross-sectional view, thefeedthrough 345 has a height HFT which corresponds to the depth of a cylindrical opening in theheader 314 andheader flange 334. The depth of the cylindrical opening is the equivalent of the thickness of theheader 314 and theheader flange 334. Thus the height HFT of thefeedthrough 345 may be altered by varying the thicknesses of theheader 314 and theheader flange 334 in order to provide a desired nominal feedthrough impedance value ZF. In this manner, the feedthrough impedance value ZF of one or more pins of the TO-header can be designed according to the impedance of thesemiconductor laser 332. It is desirable that the nominal impedance of the feedthrough 345B match the nominal impedance of thesemiconductor laser 332. -
FIG. 7C illustrates a magnified perspective view of thefeedthrough 345 which better illustrates its shape being described as a hollow circular cylinder. - Referring now to
FIG. 8A , an exploded view illustrating the assembly of thepin 316A, aglass cap 802, and thefeedthrough 345A to theheader 314 is illustrated. - In one embodiment of assembly, the
pin 316A may first be inserted into the center of thecylindrical opening 804 in theheader 314 andheader flange 334. A desired molten dielectric is poured around the pin to fill in thecylindrical opening 804 and form thefeedthrough 345A around thepin 316A. Molten glass is then poured onto the base of the package to cover around the bottom of the feedthrough around the pin and onto a bottom side of theheader 314. The molten glass is allowed to cool into a solid state and forms a hermetic seal around the pin and the feedthrough to keep dirt and moisture out of the inside of the package. - In another embodiment of assembly, press fitting of solids are used with the glass cap being hermetically sealed at the end. The
pin 316A is press fit into thecylindrical opening 701 of asolid feedthrough 345A. Thefeedthrough 345A and pin assembly. 316A is press fit into theopening 804 in theheader 314 andheader flange 334. Acylindrical opening 801 in the center of theglass cap 802 is slid over the pin at the outer end opposite thepost end 204. Asolid glass cap 802 is slid along thepin 316A to meet the bottom of theheader 314. The outer radius of the glass cap is larger than the outer radius R2 of the feedthrough in order to seal over theopening 804. The inner radius of theglass cap 802 is near the radius of thepin 316. Theglass cap 802 can then be heated in a number of ways to hermetically seal around theopening 804 and thepin 316A. - Referring now to
FIG. 8B , a magnified cross-section view of the final assembly in either case is illustrated. Thepin 316A is inserted into thecylinder 701 of thefeedthrough 345A to form theheader post 204A. Thefeedthrough 345A is inserted into theopening 804 in theheader 314 and theheader flange 334. Theglass cap 802 hermetically seals around opening 801 at thepin 316A and around theopening 804 and thefeedthrough 345A in the bottom of theheader 314 as illustrated. - The
pin 316A being a metal provides a conductive path to a terminal of a device that may be mounted inside the package. Thepin 316A may have an impedance (i.e. resistance, inductance, and capacitance) associated with it. - The
feedthrough 345A is formed of a dielectric material to insulate the pin from shorting to the header and header flange and to provide impedance matching. The dielectric constant of the feedthrough material is important to provide impedance matching. The feedthrough impedance ZF is seen as a result of the pin extending through a groundedheader 314 andheader flange 334. This is similar to a coaxial cable with a center pin and an outer ground cylindrical shell used in seventy five ohm coaxial cable. - The
feedthrough 345 can be designed in its dimensions (i.e., R1 and R2 or th; HFT) and by the selection of dielectric materials for a given pin to provide a desired nominal feedthrough impedance ZF at a frequency or over a range of frequencies. The selection of the pin diameter and conductive material can also be used to alter the feedthrough dimension R1 and influence the feedthrough impedance. The selection of the thickness of the header and header flange can also be used to alter the feedthrough dimension HFT and influence the feedthrough impedance. - With or without the impedance controlled
circuit 202, the header's feedthrough impedance ZF should be designed to match the impedance ZL of thesemiconductor laser 332 to minimize reflections at high frequencies caused by impedance mismatches. The header's feedthrough impedance ZF is the impedance seen as apin 316 feeds up through thefeedthrough 345 into theheader 314 and theheader flange 334 and extending out into theheader post 204. The feedthrough impedance can be designed with proper selection of materials and sizing of thefeedthroughs 345. - Referring now to
FIG. 9 , a bottom view of a pin-out for a three and a four pin header is illustrated.Pins semiconductor laser 332 and themonitoring photodiode 330. In line with the center C of the package and perpendicular to the header is an optical axis of thelight output 342 of thesemiconductor laser 332. Thepins - In
FIG. 9 , twopins 316C are illustrated.Pins 316C do not feedthrough past the header and into the inner chamber of the package.Pins 316C mechanically and electrically couple to the bottom of theheader 314.Pins 316C are electrically coupled through theheader 314 to theheader flange 334.Pins 316C are usually coupled to ground in order to ground out theheader 314,header flange 334, and the can or cap 312. - In a three pin header, only one of the two
pins 316C illustrated inFIG. 9 is utilized in conjunction with thepins pins 316C illustrated are utilized in conjunction with thepins - In the following discussion, the feedthrough type pins 316A and 316B are discussed without any further discussion of
pins 316C. It being understood that at least onepin 316C exists that couples to the bottom of theheader 314. - In order to use the same slanted window can 312 and conform to external optical interfaces, it is desirable to keep the
light output 342 centered in the packaged semiconductor laser and in thewindow 318. However, theheader flange 334 of theheader 314 may be altered by moving thepins 316 while maintaining the desired dimensions of thefeedthroughs 345 for impedance matching purposes. In the following discussion the feedthrough type pins are moved closer to center in order to reduce bond wire length and their inductance for better high speed performance without use of an impedance controlledcircuit 202. But for noted exceptions, the photodiode and the semiconductor laser are generally mounted within the device package as is discussed previously with reference toFIG. 3D and discussed below with reference toFIGS. 13A-13B . - Referring now to
FIGS. 10A and 10B , a modifiedheader flange 334′ of theheader 314′ is illustrated. The modifiedheader flange 334′ has onepin 316B andfeedthrough 345B offset and moved closer to thesemiconductor laser 332 while theother pin 316A andfeedthrough 345A remain at the same standard position. From a bottom view with theheader flange 334′ flipped around sideways, thepins 316 appear spaced apart as illustrated inFIG. 10B .Pin 316B is offset closer to center C thanpin 316A. - A
bond wire 360F couples at one end to theheader post 204B and at an opposite end to a pad of thesemiconductor laser 332. With thepin 316B andfeedthrough 345B offset and moved closer to thesemiconductor laser 332, thebond wire 360F is shorter than it might otherwise be. The reduction in length of the bond wire reduces the inductance there between. - The
feedthrough 345B is properly designed so that the feedthrough impedance ZF matches the input impedance ZL of thesemiconductor laser 332. - Referring now to
FIGS. 11A and 11B , a modifiedheader flange 334″ of theheader 314″ is illustrated. The modifiedheader flange 334″ has bothpins feedthroughs FIG. 11B .Pins - As before, the
bond wire 360F couples at one end to theheader post 204B and at an opposite end to a pad of thesemiconductor laser 332. The reduction in length of thebond wire 360F reduces its inductance. Thefeedthrough 345B is properly designed so that the feedthrough impedance ZF matches the input impedance ZL of thesemiconductor laser 332.Feedthrough 345A may be similarly designed to match the input impedance ZL of thesemiconductor laser 332 or otherwise designed to match the output impedance of the photodiode. Impedance matching with the photodiode is not as important as it is with the semiconductor laser. - In order to accommodate the movement of
pin 316A and thepost 204A, the devices inside the package can be modified to maintain the center of thelaser output 342. - In
FIG. 11A , thesubmount area 331 of thephotodiode 330 is modified to maintain the center of thelaser output 342. Anotch 1100 is cut into thesubmount portion 331″″ of thephotodiode 330″″ so that it accepts the tighter position of thepost 204A and pin 316A. Abond wire 360C′ is coupled between thepost 204A and thephotodiode 330″″. The length ofbond wire 360C′ is also reduced and lowers its inductance as a result. Otherwise similar labeled elements are similar to those ofFIG. 10A . - Referring now to
FIGS. 12A-12B , alternate embodiments to the submount modification to that ofFIG. 11A are illustrated with the same pin and header configuration of the device package. - In
FIG. 12A , a thin submount 331v and photodiode 330v (i.e., they are narrow) are provided to maintain the center of thelaser output 342. Thelight receiving area 340′ although thinner is somewhat compensated by extending out the end of the photodiode. Thesubmount 331 v includes awider contact 343 v to which a bond wire 360E1′ from thesemiconductor laser 332 can couple. Abond wire 360C″ is coupled between thepost 204A and thephotodiode 330 v. Otherwise similar labeled elements are similar to those ofFIG. 11A . - The
submount 331 v andphotodiode 330 v are more readily manufacturable than making thenotch 1100 in thesubmount portion 331″″ as is illustrated inFIG. 11A . The scribe lines along the edge of thesubmount 331 v andphotodiode 330 v are straight and can be scribed readily on a semiconductor wafer. - In
FIG. 12B , a separate thin submount 331 V (i.e., it's narrow) is provided from that of aseparate photodiode 330 V′ to maintain the center of thelaser output 342. Thelight receiving area 340 of thephotodiode 330 V′ remains the same as the original design. Thesubmount 331 V′ includes thewider contact 343 v to which the bond wire 360E1′ can couple to as previously described. Abond wire 360C′″ is coupled between thepost 204A and thephotodiode 330 V′. Otherwise similar labeled elements are similar to those ofFIG. 11A . - The
submount 331 V′ andphotodiode 330 V′ are more readily manufacturable than making thenotch 1100 in thesubmount portion 331″″ as is illustrated inFIG. 11A . The scribe lines along the edge of thesubmount 331 v andphotodiode 330 v are now straight and can be scribed readily on a semiconductor wafer. Thelight receiving area 340 ofphotodiode 330 V′ needs no compensation inFIG. 12B . -
FIGS. 3A-3D illustrate the device package for the packagedsemiconductor laser 300 as being a TO package with a four pin TO-header. It is understood that the number of pins and the header may vary depending upon the application and whether or not power monitoring is provided. To keep costs low, theheader 314 can be a standard conventional header size dimensionally for a TO package. - Referring now to
FIGS. 13A-13B , a three pin TO package for a packagedsemiconductor laser 300′ is illustrated. The packaged semiconductor laser may also be referred to herein as a packaged transmitter. The packagedtransmitter 300′ includes a slanted window can 1312, aheader 1314, and three leads 316. The slanted window can 1312 includes a slant lid or angled top 1317, aglass window 1318, awindow opening 1319, and acan tab 1320. Thecan tab 1320 mates with arectangular slot 1322 in theheader 1314 for proper alignment of theslant lid 1317 with theheader 1317. - Referring now to
FIG. 13B , a cut away side view of the packagedtransmitter 300′ is illustrated. Theglass window 1318 is hermetically sealed to the inside surface of the slanted window can 1312. More particularly, theglass window 1318 is hermetically sealed to the inside surface of theslant lid 1317 of the slanted window can 1312. Theglass window 1318 has a circular shape and a diameter to cover over thewindow opening 1319 of theslant lid 1317 to seal out dust and dirt. The hermetic seal between the glass window and the slanted window can 1312 further prevents moisture from seeping into the packaged transmitter. - Inside the packaged
transmitter 300′ is asilicon photodiode 1330 and a surface emittingsemiconductor laser 1332, such as a vertical cavity surface emitting laser (VCSEL) 1332. Thephotodiode 1330 is attached to aheader flange 1334 of theheader 1314. Thephotodiode 1330 has a submount portion. TheVCSEL 1332 is attached to a top surface of the submount portion of thephotodiode 1330. TheVCSEL 1332 is not mounted or attached to theheader 1314 in order to keep short the wire bond lengths to the header posts. - The embodiments of the headers (i.e.,
headers - The packaged
semiconductor laser 300′ not only includes a semiconductor laser but provides a monitoring photodiode to allow for automatic power control (APC) of the output laser beam. The slanted window can or cap with its window is important in the provision of automatic power control (APC). - Referring now to
FIG. 14A , a magnified cut away side view of the packagedtransmitter FIG. 14A illustrates the function of the slanted window can or cap. As illustrated inFIG. 14A , the slanted window can or cap supports thewindow 1318 on an angle to normal, above and aligned with the semiconductor laser 32 to receive a laser beam output from thesemiconductor laser 1332. Thewindow 1318 in the slanted window can or cap functions as a beam splitter to proportionally split theincident laser beam 1460 it receives from thesemiconductor laser 1332. - A deflected
portion 1462 of theincident laser beam 1460 is deflected or reflected by thewindow 1318 to thephotodiode 1330. Anon-deflected portion 1462 of theincident laser beam 1460 is transmitted through thewindow 1318 outside of the packagedlaser transmitter portion 1462 is used to monitor the output power in thenon-deflected portion 1462 as they are proportional to each other. The laser driver circuitry in response to monitoring the power in the deflectedportion 1462, adjusts the drive current provided to the semiconductor laser and the power of thelaser beam 1460. - The packaged
transmitter laser driving circuitry 1450 are assembled together as part of a fiber optic transceiver module. Thephotodiode 1330 is attached to theheader flange 1334 using a die attach epoxy 1350. TheVCSEL 1332 attaches to the submount portion of thephotodiode 1330 using a die attach epoxy as well. The die attach epoxy 1350 is a conductor allowing an electrical contact to be made between theVCSEL 1332 and a first contact pad of the submount portion of thephotodiode 1330. Similarly the die attach epoxy 1350 allows an electrical contact to be made between thephotodiode 1330 and theheader flange 1334. The slanted window can 1312 is coupled to theheader 1314 by aweld seal 1352. Theglass window 1318 is attached to a back surface of theslant lid 1317 by thehermetic seal 1370. - The three leads 316 are separately labeled 316A, 316B, and 316C in
FIG. 14A to describe the electrical connections between the packagedtransmitter 300 OR 300′ and thelaser driving circuitry 1450.Lead 316C couples to ground at one end and theheader flange 1334 at an opposite end. One of the bond wires couples between a first contact pad of the submount portion of thephotodiode 1330 and theheader flange 1334. One of two terminals of theVCSEL 1332 electrically couples to theheader flange 1334.Lead 316A couples to a terminal of thephotodiode 1330 at one end and a monitoring input of thelaser driving circuitry 1450 at another end. Aphoto current 1454 of thephotodiode 1330 couples to thelaser driving circuitry 1450 throughlead 316A.Lead 316B is coupled to the output of thelaser driving circuitry 1450 at one end and a second terminal of theVCSEL 1332 at an opposite end. Thelaser driving circuitry 1450 provides a laser drive current 1456 to theVCSEL 1332 to turn it on and off throughlead 316B. Thelaser driving circuitry 1450 receives adata input 1452 in order to modulate data onto an optical output of the packagedtransmitter - When an external power source is provided to the packaged
transmitter laser driving circuitry 1450, theVCSEL 1332 andphotodiode 1330 can be powered up and be actively operating. In this case, theVCSEL 1332 generates alaser beam 1460 which is coupled into theglass window 1318. Theglass window 1318 acts as a beam splitter and reflects a portion of the power of thelaser beam 1460 towards thephotodiode 1330 as indicated by the reflectedbeam 1462. The remaining power of thelaser beam 1460 propagates through theglass window 1318 becoming theoutput beam 1464 of the packagedtransmitter output beam 1464 is reduced from the power of thelaser beam 1460 generated by theVCSEL 1332 by the amount of power in the reflectedbeam 1462. - The
laser driving circuitry 1450 monitors thephoto current 1450 of thephotodiode 1330 in order to generate an appropriate laser drive current 1456 to automatically maintain a relatively constant power output in theoutput beam 1464 when theVCSEL 1332 is in an on state. -
FIG. 14B illustrates a magnified cross-sectional view of a portion of an embodiment of thewindow 1318. The window includes asubstrate material 1470, such as glass, quartz, or plastic. Thesubstrate material 1470 may have afirst material layer 1472 and/or asecond material layer 1474 on either side or both sides of thesubstrate material 1470. That is, thewindow 1318 illustrated inFIG. 14B may include thesubstrate 1470 and thematerial layer 1472, thesubstrate 1470 and thematerial layer 1474, or thesubstrate 1470 and the materials layers 1472 and 1474. Each of thematerial layers 1472 and/or 1474 may be formed of a thickness proportional to the wavelengths of the light that desire reflecting and/or transmission. The material layers 1472 and/or 1474 may be standard dielectric coating materials to allow transmission and deflection of light in one direction while reflecting light in another direction. That is,material layer 1472 in conjunction with thesubstrate layer 1470 and thematerial layer 1474 may provide beam splitting to light in a laser beam exiting from the semiconductor laser. Thematerial layer 1474 may have an antireflection coating to keep light outside the package from entering into the package. - The
material layer 1472 and or thematerial layer 1474 provides reflection of anincoming light beam 1466 into the reflectedoutput light beam 1466′. Thematerial layer 1472 and or thematerial layer 1474 allow a portion of thelight beam 1460 from the semiconductor laser to pass through thewindow 1318 as theoutput light beam 1464. That is, thematerial layer 1472 and or thematerial layer 1474 allow thelight beam 1460 from the semiconductor laser to be power split into atransmission portion 1464 and adeflection portion 1462 as illustrated. -
FIG. 14C illustrates a magnified cross-sectional view of a portion of another embodiment of the window,window 1318′. Thewindow 1318′ includes thesubstrate material 1470, such as glass, plastic quartz or other optical material. Thewindow 1318′ further includes a plurality of layers on one or both sides of thesubstrate 1470. A first plurality of layers may be alternating pairs ofmaterial layers 1472 a-1472 n on an outer side of thesubstrate 1470. A second plurality of layers may be alternating pairs ofmaterial layers 1474 a-1474 n on an inner side thesubstrate material 1470. The first plurality and the second plurality need not be alternating pairs of material layers but multiple layers. That is, thewindow 1318′ illustrated inFIG. 14C may include thesubstrate 1470 and the first plurality of pairs of alternatingmaterial layers 1472 a-1472 n, thesubstrate 1470 and the plurality of alternating pairs ofmaterial layers 1474 a-1474 n, or thesubstrate 1470 and the plurality of alternating pairs ofmaterial layers 1472 a-1472 n and 1474 a-1474 n on each respective side of the substrate. - Each of the plurality of
material layers 1472 a-1472 n and/or 1474 a-1474 n may be formed of a thickness proportional to the wavelengths of the light that desire beam splitting. The alternating pairs ofmaterial layers 1472 a-1472 n and/or 1474 a-1474 n may be standard dielectric coating materials to allow beam splitting. - The plurality of
material layers 1472 a-1472 n and/or the plurality ofmaterial layers 1474 a-1474 n provide reflection for theincoming light beam 1466 into the reflectedlight beam 1466′. The plurality of alternating pairs ofmaterial layers 1472 a-1472 n and or the plurality of alternating pairs ofmaterial layers 1474 a-1474 n allow thelight beam 1460 from the semiconductor laser to be power split into atransmission portion 1464′ and adeflection portion 1462′ as illustrated. - Referring now to
FIG. 15A , an exploded view of a FiberOptic Transceiver Module 1500 is illustrated.FIGS. 15A-15B illustrates how a packaged semiconductor laser ortransmitter 1510 is assembled into anoptical block 1502. The packaged semiconductor laser ortransmitter 1510 is the packagedsemiconductor lasers - The
Fiber optic module 1500 includes anoptical block 1502, a transmit printed circuit board (PCB) 1506, a receive printedcircuit board PCB 1508, an optional internal shield 1509, a packagedtransmitter 1510, a packagedreceiver 1511, acover 1519, analignment plate 1551, anose receptacle 1552, anose shield 1553, and abase 1555. Thealignment plate 1551 provides alignment between theoptical block 1502 and a fiber optic cable plugged into thenose receptacle 1552. Thenose receptacle 1552 includes anoptical fiber opening 1572 to receive an optical fiber connector and hold the optical fiber substantially fixed and aligned in place. Thenose shield 1553 includes anopening 1574 for insertion over thenose receptacle 1552 and is conductive to reduce EMI. - The packaged
transmitter 1510 and packagedreceiver 1511 are optoelectronic devices. An optoelectronic device is a device which can convert or transduce light or photons into an electrical signal or an electrical signal into light or photons. The packagedtransmitter 1510 includes a vertical cavity surface emitting laser (VCSEL) 1590 that converts an electrical signal into light or photons. The packagedreceiver 1511 is a packaged photodetector, including aphotodetector 1592 that detects or receives light or photons and converts them into an electrical signal and is also preferably package in a TO can. The packagedtransmitter 1510 is inserted into anopening 1564 in theoptical block 1502 and epoxied thereto. The packagedreceiver 1511 is inserted into anopening 1563 inoptical block 1502 and epoxied thereto. - The packaged
transmitter 1510 hasterminals 1560 to couple to through-holes of the transmitPCB 1506. Theterminals 1560 are soldered to make an electrical connection to the transmitPCB 1506. The transmitPCB 1506 includeselectrical components 1512 such as the laser driver circuitry and pins 1513. Theelectrical components 1512 control the packagedtransmitter 1510 and buffer the data signal received from a system throughpins 1512 for transmission over an optical fiber. - The packaged
receiver 1511 hasterminals 1561 to couple to through-holes of the receivePCB 1508. Theterminals 1561 are soldered to make an electrical connection to the receivePCB 1508. The receive PCB 108 includeselectrical components 1516 such as a receiver integrated circuit (transimpedance amplifier and post amplifier), and pins 1517. Theelectrical components 1516 control the packagedreceiver 1511 and buffer the data signal received from an optical fiber. - Referring now to
FIG. 15B , a cross-sectional view of theoptical block 1502 is illustrated assembled in thefiber optic module 1500. Thepackage transmitter 1510, the packagedreceiver 1511, and thealignment plate 1551 are coupled to theoptical block 1502. Theoptical block 1502 includes lenses 1520-1523 and reflectors 1524-1525.Lens 1523 is for collimating the light or photons diverging from the packagedtransmitter 1510.Lens 1522 is for focussing the collimated light or photons into an optical fiber.Lens 1520 is for collimating the light or photons diverging out from the end of an optical fiber into theoptical block 1502.Lens 1521 is for focusing the collimated light or photons into the packagedreceiver 1511. Reflectors 1524-1525 are forty five degree angle facets formed in theoptical block 1502 to provide total internal reflection and redirect the light rays between the optical fibers and the optoelectronic devices. The facets may be coated with a reflective surface or mirror surface to reflect light or photons off the reflective coated surface or facets having an optical grating surface to reflect photons. However, none of the elements of theoptical block 1502 are used to redirect a light beam or ray back into the packagedtransmitter 1510. That is, thelens 1523,reflector 1525,lens 1522 associated with the packagedtransmitter 1510, are used to couple light forward into an optical fiber and not to reflect light back into the packagedtransmitter 1510. - The packaged
transmitter 1510 includes a semiconductor laser such as a vertical cavitysurface emitting laser 1590 for generation of light or photons in response to electrical signals from the transmitPCB 1506. - Light or photons emitted by the packaged
transmitter 1510 are coupled intolens 1523 and collimated onto thereflector 1525 at an incident angle I1 (angle with the perpendicular toreflector 1525 surface) of substantially forty five degrees.Reflector 1525 reflects the incident light or photons on a refraction angle R1 (angle with the perpendicular toreflector 1525 surface) equivalent to incident angle I1 of substantially forty five degrees. The reflected light or photons travel perpendicular to the incident light or photons towards thelens 1522.Lens 1522 focuses the light or photons from the packagedtransmitter 1510 into an aligned optical fiber through anoptical port 1567 in thealignment plate 1551. Thus, light or photons coupled or launched into an optical fiber, defining a first optical axis, are substantially perpendicular to the light or photons emitted and incident uponlens 1523 from the packagedtransmitter 1510. - Referring now to
FIG. 16A , an exploded view of afiber optic module 1600 is illustrated.FIGS. 16A-16B illustrate how a packaged semiconductor laser ortransmitter 1620 is assembled into an SC fiber optic plug orconnector 1650A. The packaged semiconductor laser ortransmitter 1620 is the packagedsemiconductor lasers - The fiber-
optic module 1600 includes acover 1601, amodule chassis frame 1602, a printed circuit board (PCB) 1610, a packagedtransmitter 1620, a packagedreceiver 1621, a pair of shieldingcollars connectors U-Plate 1624. The optical, electrical and opto-electronic components of the fiber-optic module 1600 are assembled into themodule chassis frame 1602 and thecover 1601 is then fitted to themodule chassis frame 1602. - The
module chassis frame 1602 includes optical connector receptacles 1603 (including openings 1604), and abase 1606. Theopenings 1604 are SC optical connector openings for a duplex SC optical connection. Theoptical connector openings 1603 are separated by aslot 1638. - The packaged
transmitter 1620 may include the vertical cavity surface emitting laser (VCSEL) for transmitting optical signals. The packagedreceiver 1621 includes a photodiode for receiving optical signals. Each package of thepackage transmitter 1620 and the packagedreceiver 1621 may be a standard TO package. Each of the packagedtransmitter 1620 andreceiver 1621 have one ormore terminals 1619 which couple to the edge traces 1614 (1614T and 1614B) on each side of the printedcircuit board 1610. - The printed
circuit board 1610 includes one or more PCB signal pins 1612, edge traces 1614 on each side for mounting the packagedtransmitter 1620 and the packagedreceiver 1621, and one or moreintegrated circuits 1616 for processing signals between the signal pins 1612 and the packagedtransmitter 1620 and the packagedreceiver 1621. The one or more integrated circuits includes the laser driver circuitry previously discussed. - The SC fiber optic plugs or
connectors lens ports lenses transmitter 1620 and packagedreceiver 1621 respectively. Each of theSC connectors snap lock clips 1652 each having a retainingprotrusion 1653, ferrule barrels 1654, support struts 1656 in a front portion. Each of theSC connectors headers respective flanges 1655 in a rear portion. Each of the circular recesses 1657 mates with theU-shaped openings 1627 of theU-plate 1624. - The packaged
transmitter 1620 is mounted inside thetransmitter port 1623A of the SC fiber optic plug orconnector 1650A to form a Transmitter Optical Subassembly. Theshielding collar 1622A is slid over theport 1623A. Theterminals 1619 of the packagedtransmitter 1620 are then soldered onto thePCB 1610. - The packaged
receiver 1621 is mounted inside thereceiver port 1623B of the SC fiber optic plug orconnector 1650B to form a Receiver Optical Subassembly. Theshielding collar 1622B is slid over theport 1623B. Theterminals 1619 of the packagedreceiver 1621 are then soldered onto thePCB 1610. - The optical, electro-optical, and the electronic components are assembled into the
module chassis frame 1602 before thecover 1601 encloses it. The front portion of theSC connectors openings 1603 in the nose of themodule chassis frame 1602. TheU-plate 1624 is coupled to the module chassis frame so that its U-openings 1627 fit into the circular recesses 1657 of eachrespective connector U-plate 1624 holds the subassembly of the optical and electrical components coupled into themodule chassis frame 1602. - Referring now to
FIG. 16B , a cross-sectional view of the SC optical plugs orconnectors fiber optic module 1600. Thepackage transmitter 1620 is mounted inside thetransmitter port 1623A of the SC fiber optic plug orconnector 1650A. Theshielding collar 1622A is around theport 1623A. Theterminals 1619 of the packagedtransmitter 1620 are soldered onto thePCB 1610. The packagedreceiver 1621 is mounted inside thereceiver port 1623B of the SC fiber optic plug orconnector 1650B. Theshielding collar 1622B is around theport 1623B. Theterminals 1619 of the packagedreceiver 1621 are soldered onto thePCB 1610. - The SC fiber optic plugs or
connectors lens 1651A and thelens 1651B mounted insideports lens 1651A is between thefiber ferrule 1654 and the packagedtransmitter 1620. Thelens 1651B is between thefiber ferrule 1654 and the packagedreceiver 1621. - As previously discussed, the packaged
transmitter 1620 includes the vertical cavity surface emitting laser (VCSEL) for generation of light or photons in response to electrical signals from thePCB 1610. Light or photons emitted by the packagedtransmitter 1620 are coupled intolens 1651A, collimated and focused into an aligned optical fiber plugged into the SCfiber optic plug 1650A. Thus, light or photons from the packagedtransmitter 1620 are coupled or launched into an optical fiber through thelens 1651A. - None of the elements of the SC fiber optic plug or
connector 1650A are used to redirect a light beam or ray back into the packagedtransmitter 1620. That is, thelens 1651A associated with the packagedtransmitter 1620, is used to couple light forward into an optical fiber and not to reflect light back into the packagedtransmitter 1620. - In summary, the following have been previously described herein: (1) A high-bandwidth TO-header based packaging for VCSEL; (2) A packaging scheme to arrange a VCSEL and a PCB circuit on a TO-header; (3) Impedance control of the feedthrough of the pins of the TO-header is, according to the resistance of the VCSEL; (4) An Impedance-controlled circuit as a medium for shortening of wire bonds to reduce the inductance of terminals of the device package; (5) The impedance-controlled circuit can have different impedance to match the resistance of different VCSELs used; (6) Thick wire bond wire (or ribbon wire) for reducing inductance introduced by wire bonding; (7) Packaging scheme for a VCSEL on a submount to provide a short bond wire length; (8) A submount to provide mechanical support to the VCSEL, and including a photodetector to generate a monitor current; (9) Electrical vias in the submount for shorting a ground contact of the VCSEL to the top of the header as a means of grounding the VCSEL; (10) A slanted TO-cap used for partial reflection of light from the laser back to the monitor photodetector for automatic power control application; and (11) The slanted TO-cap being oriented relative to the monitor photodiode (submount of the VCSEL) to get a maximum amount of monitoring current.
- While certain exemplary embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that this invention not be limited to the specific constructions and arrangements shown and described, since various other modifications may occur to those ordinarily skilled in the art.
Claims (37)
1-50. (canceled)
51. A packaged semiconductor laser transmitter for high modulation bandwidth, the packaged semiconductor laser transmitter comprising:
a thin-outline device package including a thin-outline header having a feedthrough pin with a first impedance;
a semiconductor laser mounted within the thin-outline device package, the semiconductor laser having an electrical contact with a second impedance;
an impedance-controlled circuit coupled between the feedthrough pin of the thin-outline header and the electrical contact of the semiconductor laser, the impedance-controlled circuit having a third impedance at one contact point and a fourth impedance at another contact point; and
wherein the third impedance of the impedance-controlled circuit to match the first impedance of the feedthrough pin of the thin-outline header, the fourth impedance of the impedance-controlled circuit to match the second impedance of the electrical contact of the semiconductor laser, and the impedance-controlled circuit to provide a low impedance in a first interconnect between the semiconductor laser and the impedance-controlled circuit and a low impedance in a second interconnect between the feedthrough pin of the thin-outline header and the impedance-controlled circuit for high modulation bandwidth.
52. The packaged semiconductor laser transmitter of claim 51 , wherein
the first impedance of the feedthrough pin of the thin-outline header differs from the second impedance of the electrical contact of the semiconductor laser, and
the impedance-controlled circuit compensates for the difference between the first impedance and the second impedance.
53. The packaged semiconductor laser transmitter of claim 51 , wherein
the first impedance of the feedthrough pin of the thin-outline header matches the second impedance of the electrical contact of the semiconductor laser, and the third impedance and the fourth impedance of the impedance-controlled circuit matches the first impedance and the second impedance, respectively.
54. The packaged semiconductor laser transmitter of claim 53 , wherein
the second impedance of the electrical contact of the semiconductor laser is fifty ohms over a given frequency range and the first impedance of the feedthrough pin of the thin-outline header is fifty ohms over the given frequency range, and
the third impedance and the fourth impedance of the impedance-controlled circuit are fifty ohms over the given frequency range.
55. The packaged semiconductor laser transmitter of claim 51 further comprising:
a window can coupled to the thin-outline header, the window can having a window to allow a first portion of a laser beam from the semiconductor laser to pass through and out from the packaged semiconductor laser transmitter.
56. The packaged semiconductor laser transmitter of claim 55 further comprising:
a photodetector mounted within the thin-outline device package, and
wherein the window can is a slanted window can having a window to redirect a second portion of the laser beam from the semiconductor laser to the photodetector.
57. The packaged semiconductor laser transmitter of claim 56 , wherein
the photodetector mounted within the thin-outline device package to receive the second portion of the laser beam to facilitate automatic power control of the semiconductor laser.
58. The packaged semiconductor laser transmitter of claim 51 , wherein
the impedance-controlled circuit includes at least one impedance control line to provide the third impedance at the one contact point and the fourth impedance at the another contact point.
59. The packaged semiconductor laser transmitter of claim 58 , wherein
the impedance-controlled circuit further includes a printed circuit board and the at least one impedance control line is on top of the printed circuit board.
60. The packaged semiconductor laser transmitter of claim 51 , wherein
the first interconnect and the second interconnect are a first bond wire and a second bond wire, respectively, and
the semiconductor laser, the impedance-controlled circuit, and the feedthrough pin of the thin-outline header are positioned with respect to each other within the thin-outline device package to minimize a length of the first bond wire and a length of the second bond wire.
61. The packaged semiconductor laser transmitter of claim 58 , wherein
the first interconnect and the second interconnect are a first bond wire and a second bond wire, respectively,
the semiconductor laser, the impedance-controlled circuit, and the feedthrough pin of the thin-outline header are positioned with respect to each other within the thin-outline device package to minimize a length of the first bond wire and a length of the second bond wire, and
with respect to the thin-outline header, a height of a top surface of the semiconductor laser, a height of a top surface of the at least one control line, and a height of a top surface of the feedthrough pin of the thin-outline header are substantially equal to further minimize the length of the first bond wire and the length of the second bond wire.
62. The packaged semiconductor laser transmitter of claim 60 , wherein
the first bond wire is a first plurality of bond wires and the second bond wire is a second plurality of bond wires, respectively, to reduce inductance in the first interconnect and the second interconnect, respectively.
63. The packaged semiconductor laser transmitter of claim 60 , wherein
the first bond wire and the second bond wire are thick bond wires to reduce inductance in the first interconnect and the second interconnect, respectively.
64. The packaged semiconductor laser transmitter of claim 60 , wherein
the first bond wire and the second bond wire are ribbon bond wires to reduce inductance in the first interconnect and the second interconnect, respectively.
65. The packaged semiconductor laser transmitter of claim 51 , wherein
the semiconductor laser is a vertical cavity surface emitting laser.
66. The packaged semiconductor laser transmitter of claim 51 further comprising:
a submount mounted within the thin-outline device package and coupled between a bottom surface of the semiconductor laser and a top surface of the thin-outline header.
67. The packaged semiconductor laser transmitter of claim 66 , wherein
the submount has one or more vias to conductively couple the bottom surface of the semiconductor laser to the thin-outline header.
68. The packaged semiconductor laser transmitter of claim 66 further comprising:
a conductive block mounted within the thin-outline device package, a bottom surface of the conductive block conductively coupled to the thin-outline header, a top surface of the conductive block conductively coupled to a top surface of the submount, the conductive block to minimize a total number of bond wires and to lower inductance.
69. A method of packaging a semiconductor laser to provide high modulation bandwidth, the method comprising:
matching a feedthrough impedance of a first pin of a device package to an input impedance of a semiconductor laser at an input contact; and
minimizing an inductance in an interconnect between the first pin and the input contact of the semiconductor laser.
70. The method of claim 69 , wherein
the minimizing of the inductance in the interconnect includes
minimizing a length of a first bondwire coupled between the first pin and the input contact of the semiconductor laser.
71. The method of claim 70 , wherein
the minimizing of the inductance in the interconnect further includes
maximizing a cross sectional area of the first bondwire coupled between the first pin and the input contact of the semiconductor laser.
72. The method of claim 69 , wherein
the minimizing of the inductance in the interconnect includes
minimizing a distance between the first pin and the input contact of the semiconductor laser.
73. The method of claim 72 , wherein
the minimizing of the inductance in the interconnect further includes
providing a plurality of bondwires coupled between the first pin and the input contact of the semiconductor laser.
74. The method of claim 72 , wherein
the minimizing of the inductance in the interconnect further includes
leveling a surface of the input contact of the semiconductor laser with a top surface of a post of the first pin.
75. The method of claim 72 , wherein
the minimizing of the inductance in the interconnect further includes
mounting the semiconductor laser within a device package to level a surface of the input contact of the semiconductor laser with a top surface of a post of the first pin.
76. The method of claim 69 further comprising:
matching a feedthrough impedance of a second pin of the device package to an input impedance of a photodetector at an input contact.
77. The method of claim 76 further comprising:
minimizing an inductance in an interconnect between the second pin and the input contact of the photodetector.
78. The method of claim 69 further comprising:
redirecting a portion of a laser beam from the semiconductor laser to a photodetector, and
monitoring the photocurrent generated by the photodetector in response to the redirected portion of the laser beam to obtain a measure of an optical power output in the portion of the laser beam exiting from the device package.
79. The method of claim 78 further comprising:
automatically controlling the optical power output from the device package in response to the monitoring of the photocurrent.
80. A transmitter optical subassembly comprising:
a fiber optic connector having a port;
a packaged transmitter for high modulation bandwidth, the packaged transmitter having a light emitting end mounted into the port of the fiber optic connector, the packaged transmitter including
a thin-outline device package including a thin-outline header having a feedthrough pin with a feedthrough impedance;
a semiconductor laser mounted within the thin-outline device package to provide a low impedance in a first interconnect coupled between the feedthrough pin and an electrical contact of the semiconductor laser, the electrical contact of the semiconductor laser having an input impedance; and
wherein the feedthrough impedance of the feedthrough pin of the thin-outline header to substantially match the input impedance of the electrical contact of the semiconductor laser.
81. The transmitter optical subassembly of claim 80 further comprising:
a lens mounted into the port of the fiber optic connector in front of the light emitting end of the packaged transmitter, the lens to collimate light exiting from the packaged transmitter into a fiber optic cable.
82. The transmitter optical subassembly of claim 80 , wherein
the packaged transmitter further includes
a window can coupled to the thin-outline header, the window can having a window to allow a first portion of a laser beam from the semiconductor laser to pass through and exit the packaged transmitter at the light emitting end.
83. The transmitter optical subassembly of claim 82 , wherein
the packaged transmitter further includes
a photodetector mounted within the thin-outline device package, and
wherein the window can is a slanted window can having a window to redirect a second portion of the laser beam from the semiconductor laser to the photodetector.
84. The transmitter optical subassembly of claim 83 , wherein
the photodetector mounted within the thin-outline device package to receive the second portion of the laser beam to facilitate automatic power control of the semiconductor laser.
85. A fiber optic module comprising:
at least one printed circuit board;
a packaged receiver near one end coupled to the at least one printed circuit board;
a packaged transmitter for high modulation bandwidth, the packaged transmitter near the one end and including
a thin-outline device package including a thin-outline header having a post with a first impedance;
a semiconductor laser mounted within the thin-outline device package, the semiconductor laser having an electrical contact with a second impedance;
an impedance-controlled circuit coupled between the post of the thin-outline header and the electrical contact of the semiconductor laser, the impedance-controlled circuit having a third impedance at one contact point and a fourth impedance at another contact point; and
wherein the third impedance of the impedance-controlled circuit to match the first impedance of the post of the thin-outline header, the fourth impedance of the impedance-controlled circuit to match the second impedance of the electrical contact of the semiconductor laser, and the impedance-controlled circuit to provide a low impedance in a first interconnect between the semiconductor laser and the impedance-controlled circuit and a low impedance in a second interconnect between the post of the thin-outline header and the impedance-controlled circuit for high modulation bandwidth; and
a housing.
86. A fiber optic communication system comprising:
a first fiber optic module at one end;
a second fiber optic module at an opposite end;
at least one fiber optic cable coupled between the first fiber optic module and the second fiber optic module; and
at least one of the first fiber optic module and the second fiber optic module includes
at least one printed circuit board;
a packaged transmitter for high modulation bandwidth coupled to the at least one printed circuit board, the packaged transmitter including
a thin-outline device package including a header with a first pin and a second pin feeding through the header and a third pin coupled to a bottom of the header, the first pin being closer to a center of the header than the third pin, the first pin having a first feedthrough impedance and the second pin having a second feedthrough impedance,
a first feedthrough between the first pin and the header,
a second feedthrough between the second pin and the header,
a photodetector and a submount mounted within the thin-outline device package, a bottom surface of the photodetector and a bottom surface of the submount coupled to the header, the photodetector having an electrical contact on a top surface with a first input impedance,
a semiconductor laser mounted within the thin-outline device package, a bottom surface of the semiconductor laser coupled to a top surface of the submount, the semiconductor laser having an electrical contact on a top surface with a second input impedance,
a first bondwire with a first length coupled between a post of the first pin and the electrical contact of the semiconductor laser,
a second bondwire with a second length coupled between a post of the second pin and the electrical contact of the photodetector, and
wherein the first pin being closer to the center of the header than the third pin to minimize the first length and an inductance of the first bondwire; and
a housing.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
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US11/409,938 US20060192221A1 (en) | 2002-08-16 | 2006-04-24 | Methods, apparatus, and systems with semiconductor laser packaging for high modulation bandwidth |
Applications Claiming Priority (3)
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US40399802P | 2002-08-16 | 2002-08-16 | |
US10/640,972 US7061949B1 (en) | 2002-08-16 | 2003-08-13 | Methods, apparatus, and systems with semiconductor laser packaging for high modulation bandwidth |
US11/409,938 US20060192221A1 (en) | 2002-08-16 | 2006-04-24 | Methods, apparatus, and systems with semiconductor laser packaging for high modulation bandwidth |
Related Parent Applications (1)
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US10/640,972 Division US7061949B1 (en) | 2002-08-16 | 2003-08-13 | Methods, apparatus, and systems with semiconductor laser packaging for high modulation bandwidth |
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US20060192221A1 true US20060192221A1 (en) | 2006-08-31 |
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US10/640,972 Expired - Lifetime US7061949B1 (en) | 2002-08-16 | 2003-08-13 | Methods, apparatus, and systems with semiconductor laser packaging for high modulation bandwidth |
US11/409,938 Abandoned US20060192221A1 (en) | 2002-08-16 | 2006-04-24 | Methods, apparatus, and systems with semiconductor laser packaging for high modulation bandwidth |
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US10/640,972 Expired - Lifetime US7061949B1 (en) | 2002-08-16 | 2003-08-13 | Methods, apparatus, and systems with semiconductor laser packaging for high modulation bandwidth |
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