WO2001067144A2

WO2001067144A2 - Integrated optical transceiver and related methods

Info

Publication number: WO2001067144A2
Application number: PCT/US2001/007053
Authority: WO
Inventors: Michael R. Feldman; James E. Morris, Jr.
Original assignee: Digital Optics Corporation
Priority date: 2000-03-06
Filing date: 2001-03-06
Publication date: 2001-09-13
Also published as: CN100354671C; EP1269239A2; JP2003526909A; CA2401976A1; AU2001247286A1; CN1419659A; WO2001067144A3

Abstract

An optical transceiver (200) includes at least one light source (202) and at least one detector mounted on the same surface of the same substrate (206). At least one of the light source and the detector is mounted on the surface. An optics block (220) having optical elements (222, 224) for each light source and detectors is attached via a vertical spacer to the substrate. Electrical interconnections (208) for the light source and the detector are accessible from the same surface of the substrate with the optics block attached thereto. One of the light source and the detector may be monolithically integrated into the substrate.

Description

INTEGRATED OPTICAL TRANSCEIVER AND RELATED METHODS

BACKGROUND OF THE INVENTION Previous attempts at integrating a transceiver on a chip involved using monolithic integration, in which the active elements are formed in the substrate, and are thus all made of the same material. This does not allow optimum performance to be realized for at least one of the detector array and the light source array.

Other attempts have placed the active elements, e.g., the light sources and the detectors, on different substrates. However, this increases the complexity of the system due to an increased number of components and alignment difficulty.

SUMMARY OF THE INVENTION The present invention is therefore directed to an integrated optical transceiver which substantially overcomes one or more of the problems due to the limitations and disadvantages of the related art.

These and other objects may be realized by providing an optical transceiver including at least one light source on a first surface of a substrate, at least one detector on the first surface of the substrate, at least one of the at least one light source and the at least one detector being mounted on the substrate, the at least one detector to receive light other than from the at least one light source, and an optics block having optics thereon. The optics are for both the at least one light source and the at least one detector. The optics block is attached to the substrate.

The at least one light source and the at least one detector may be of different materials. One of the at least one light source and the at least one detector may be monolithically integrated with the substrate. A spacer may be provided between the substrate and the optics block. The spacer may completely surround the periphery of the optics block.

The spacer may include a plurality of separate spacers provided in the periphery of the optics block. Optics for the at least one light source and the at least one detector have the same design. Optics for the at least one light source may be formed on an opposite side of the optics block from optics for the at least one detector. The at least one light source may be a vertical cavity surface emitting laser. Interconnection features may be provided on the first surface of the substrate for the at least one light source and the at least one detector. The interconnection features may be on a same side or may be on opposite side of the first surface of the substrate for the at least one light source and the at least one detector.

The at least one light source may be an array of light sources and the at least one detector may be an array of detectors. The array of light sources and the array of detectors may be parallel or may form a line.

The above and other objects may be realized by providing a method of forming an optical transceiver including providing a plurality of detectors on a first surface of a first wafer, providing a plurality of light sources on the first surface of the first wafer, at least one of the plurality of detectors and the plurality of light sources being mounted on the first wafer, providing electrical interconnections for each of the plurality of detectors and each of the plurality of light sources on the first surface of the first wafer, providing an optics block having at least one optical element for each of the plurality of detectors and each of the plurality of light sources, providing a vertical spacer between the optics block and the first wafer, attaching the vertical spacer, the optics block and the first wafer to one another, and separating the first wafer into a plurality of transceiver, each transceiver having at least one light source and at least one detector. The providing of the optics block may include forming the at least one optical element for each of the plurality of detectors and each of the plurality of light sources on a second wafer and attaching the second wafer to the first wafer before the separating, the separating allowing access to the electrical interconnections. The providing of the vertical spacer may include forming vertical spacers for each of the transceivers on a spacer wafer and attaching the spacer wafer to the first wafer before the separating, the separating allowing access to the electrical interconnections. The providing of the optics block may include forming the at least one optical element for each of the plurality of detectors and each of the plurality of light sources on a second wafer and attaching the second wafer to the spacer wafer and the first wafer before the separating, the separating allowing access to the electrical interconnections. The attaching may include directly attaching the second wafer to the spacer wafer. The providing of one of the plurality of light sources and the plurality of detectors may include monolithically integrating into the first wafer. The providing of electrical interconnections for each of the plurality of detectors and each of the plurality of light sources may include using a same mask for both interconnections to the detectors and the light sources.

These and other objects of the present invention will become more readily apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating the preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other objects, aspects and advantages will be described with reference to the drawings, in which:

Figure 1 is an elevational exploded top view of an optical transceiver of the present invention;

Figure 2 is an elevational side view of another optical transceiver of the present invention;

Figure 3 is a top view of another configuration of the light sources and detectors on the same substrate;

Figure 4 is a schematic side view of the creation of multiple transceivers in accordance with the present invention; and Figure 5 is an exploded elevational perspective view of an interface in conjunction with fibers in a housing and the transceiver of the present invention.

DETAILED DESCRIPTION OF THE INVENTION In the following description, for purposes of explanation and not limitation, specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known devices and methods are omitted so as not to obscure the description of the present invention with unnecessary details. Rather than using monolithic integration, many of the advantages of integration can still be realized by providing the light source array and the detector array on the same surface of a single substrate and providing an optics block having the optical elements for both the light source array and the detector array integrated therein.

Related, co-pending U.S. Provisional Application Serial No.09/690,763 entitled "Fiber Interfaces Including Parallel Arrays, Power Monitoring and/or Differential Mode Delay Compensation" filed on October 18, 2000, describes a laser array and a detector array on the same substrate. In this previous application, the detector array was used for monitoring the power of the lasers, a portion of the output laser beams being directed to the detector. In accordance with the present disclosure, a light source array and a detector array are integrated on the same substrate, but, as shown in Figures 1 and 2 of the present application, these detectors are for receiving a signal from a remote location, not for monitoring the light source array. Of course, an additional array of monitor detectors could be provided for monitoring the output of the light sources.

In Figure 1 , an optical transceiver 100 includes a light source array 102, here shown as a vertical cavity side emitting laser (VCSEL) array, and a detector array 104 are integrated on a silicon wafer 106. Silicon interconnect tracks 108 supply power to the active elements 102, 106 and pads 110 allow the detector signals to be read out.

An optics block 120 contains two sets of integrated optics, one set 122 for the light source array 102 and one set 124 for the detector array 104. The integrated optics 122 for the light source receive light from the light source array 102 and direct the light to a desired application. The integrated optics 124 for the detectors receive light from a desired application and direct the light to the detector array 104. The optics may be diffractives, refractives or hybrids thereof and may be formed lithographically on the optics block 120.

The integrated optics 122, 124 for the light source array and the detector array may include optical elements formed on either or both surfaces of the optics block 120. Since the optics for both the light source array and the detector array are aligned simultaneously, the assembly and alignment steps required for creating a transceiver are reduced. Further, the integration allows the transceiver to be smaller and have fewer parts. Depending upon the material used for the substrate, either the detector array or the light source array may be monolithically integrated therein. The transceiver 100 also includes a spacer 130 between the active elements and the optics block 120. The spacer may be an integrated spacer surrounding the perimeter of the optics block, as shown in Figure 1. The spacer may be a separate element, formed in the optics block or formed in the substrate. In Figure 2, the bonded structure of a transceiver 200 is shown. Rather than having a spacer 130 around the perimeter of the optics block 120, separate spacer elements 230 are positioned at the corners of the optics block. Also, the optics 222 for the light sources 202 are on a different surface of the optics block 220 than the optics 224 for the detectors 204. These optics for both the light sources and the detectors may have the same design. Again light sources 202 and detectors 204 are on the same substrate 206, and one of them may be monolithically integrated therein. Silicon tracks 208 and pads 208 for providing power and signals to and from the active elements are also on the substrate.

Figure 3 is a top view of a transceiver 300 in accordance with another embodiment of the present invention. In Figure 3, rather than having the active elements 102, 104 arranged in parallel arrays, the active elements form a linear array. In the particular example shown in Figure 3, four light sources 102 and four detectors 104 are in a line. The spacing there between reduces cross-talk between the active devices. Corresponding optical elements 122,124 are also now in a single line. This configuration allows a standard 1 x 12 fiber array to be connected with the transceiver. This configuration also allows all the required interconnection to be provided on a same side of the substrate 106, thereby allowing the optics block 120 and the substrate 106 to share a common edge, which may facilitate manufacturing at the wafer level.

Also in Figure 3, the spacer wafer 130, in addition to surrounding the perimeter of the optics block 120, also includes an isolating portion 132 between the two types of electro- optical elements 102, 104. This isolating portion 132 may be coated with a metal to further reduce cross-talk between the electro-optical elements. The closer the electro-optical components, the more important isolation becomes. The isolating portion 132 may also be provided in any of the other configurations.

In any of the configurations, the components may be attached using wafer-to-wafer bonding techniques, as set forth, for example, in U.S. Patent Nos. 6,096,155 and 6,104,690, commonly assigned, which are hereby incorporated by reference in their entirety for all purposes. The above configurations allow the optics for both the transmitter portion and the receiver portion to be aligned simultaneously. As used herein, the term wafer is meant to generally refer to any structure having more than one component which is to be separated for final use.

A particular example of wafer bonding all three substrates together before separating is shown in Figure 4. By creating spaces 340 between the sets of optical elements 122, 124 for each transceiver and spaces 342 between the spacers 130 for each transceiver, e.g., by etching in silicon as shown, the individual transceivers may be realized by separating the substrate 106 containing the light sources 102 and detectors 304 at the appropriate points. As shown in Figure 4, the detectors 304 are monolithically integrated into the substrate 106. Whichever active element to be provided on the substrate has the higher effective yield is preferably the monolithically integrated element, since the monolithically integrated elements will not be able to be substituted out. Further, the metalization required for the electrical connections for both the monolithically integrated element and the additional active element on the substrate are formed using the same mask set as that for forming the monolithically integrated element. This helps insure precise alignment, since the active element to be mounted can use its metalization to provide its alignment, e.g., by solder self-alignment. The active elements that are to be mounted on the substrate may then be tested before being mounted. After mounting, they may be tested again and replaced if required before the wafer bonding.

As used herein, bonding may include any type of attachment, including the use of bonding materials, surface tension or directly forming on the same substrate. As used herein, separating may include any means for realizing individual components, e.g., dicing. Further examples of separating wafers when creating modules having electro-optical elements may be found in related to the commonly assigned, co-pending application entitled "Separating of Electro-Optical Integrated Modules and Structures Formed Thereby", attorney docket number DOC.072P, filed concurrently herewith, the entire contents of which are hereby incorporated by reference for all purposes. The alignment of the active elements to the input and output ports corresponding thereto, typically fibers, is particularly important. One configuration for insuring proper alignment between the transceiver and fibers is shown in Figure 5. As can be seen in Figure 5, a plurality of fibers 410 are inserted into a ferrule 412. The active elements of the present invention, here the linear configuration as shown in Figure 3, which are to be in communication with the fibers 410, are preferably provided on a silicon bench or sub- mount 416, corresponding to the common substrate 106 in Figure 3. In turn, this silicon bench 416 is preferably provided on a substrate 418. An optics block 420 provides at least one optical element between each opto-electronic device on the sub-mount 416 and a corresponding fiber 410. The optics block 420 is preferably spaced from the opto- electronic devices by a spacer 415. The optical elements preferably include elements which collimate, focus, homogenize or otherwise couple the light. Since the optics block has two surfaces, two optical elements may be provided thereon. Further, if required, additional optics blocks may be bonded to and spaced from the optics block 420 to provide additional surfaces, as with any of the previous transceiver configurations.. A mechanical interface 422 aligns the optics block 420, which is already aligned with the electro-optical devices, with the fibers 410. This may be achieved by the provision of alignment features on both the mechanical interface 422 and the ferrule 412 housing the fibers 410. In the particular example shown, these alignment features consist of holes 424 in the ferrule 412, which are already typically present for aligning the ferrule with other devices, and alignment holes 426 in the mechanical interface 422. Once these alignment holes 424, 426 are aligned, an alignment pin, not shown, may then be inserted therein to maintain the aligned position. Further details of such interfaces may be found, for example, in commonly assigned, co-pending application U.S. Serial No. 09/418,022 entitled "Optical Subassembly" which is incorporated by reference in its entirety for all purposes. While the present invention is described herein with reference to illustrative embodiments for particular applications, it should be understood that the present invention is not limited thereto. Those having ordinary skill in the art and access to the teachings provided herein will recognize additional modifications, applications, and embodiments within the scope thereof and additional fields in which the invention would be of significant utility without undue experimentation. Thus, the scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given.

Claims

1. An optical transceiver comprising: at least one light source on a first surface of a substrate; at least one detector on the first surface of the substrate, at least one of the at least one light source and the at least one detector being mounted on the substrate, the at least one detector to receive light other than from the at least one light source; and an optics block having optics thereon, said optics being for both the at least one light source and the at least one detector, the optics block being attached to the substrate.

2. The optical transceiver of claim 1 , wherein at least one light source and the at least one detector are of different materials.

3. The optical transceiver of claim 1, wherein one of the at least one light source and the at least one detector is monolithically integrated with the substrate.

4. The optical transceiver of claim 1 , wherein the at least one light source is an array of light sources and the at least one detector is an array of detectors.

5. The optical transceiver of claim 1, further comprising a spacer between the substrate and the optics block.

6. The optical transceiver of claim 5, wherein the spacer completely surround the periphery of the optics block.

7. The optical transceiver of claim 5, wherein the spacer includes a plurality of separate spacers provided in the periphery of the optics block.

8. The optical transceiver of claim 1, wherein optics for the at least one light source and the at least one detector have the same design.

9. The optical transceiver of claim 1, wherein optics for the at least one light source are formed on an opposite side of the optics block from optics for the at least one detector.

10. The optical transceiver of claim 1 , wherein the at least one light source is a vertical cavity surface emitting laser.

11. The optical transceiver of claim 1, further comprising interconnection features on the first surface of the substrate for the at least one light source and the at least one detector.

12. The optical transceiver of claim 11 , wherein the interconnection features are on a same side of the first surface of the substrate for both the at least one light source and the at least one detector.

13. The optical transceiver of claim 11, wherein the interconnection features are on opposite sides of the first surface of the substrate for the at least one light source and the at least one detector.

14. The optical transceiver of claim 4, wherein the array of light sources and the array of detectors are parallel.

15. The optical transceiver of claim 4, wherein the array of light sources and the array of detectors form a line.

16. A method of forming an optical transceiver comprising: providing a plurality of detectors on a first surface of a first wafer; providing a plurality of light sources on the first surface of the first wafer, at least one of the plurality of detectors and the plurality of light sources being mounted on the first wafer; providing electrical interconnections for each of the plurality of detectors and each of the plurality of light sources on the first surface of the first wafer; providing an optics block having at least one optical element for each of the plurality of detectors and each of the plurality of light sources; providing a vertical spacer between the optics block and the first wafer; attaching the vertical spacer, the optics block and the first wafer to one another; and separating the first wafer into a plurality of transceiver, each transceiver having at least one light source and at least one detector.

17. The method of claim 16, wherein said providing of the optics block includes forming the at least one optical element for each of the plurality of detectors and each of the plurality of light sources on a second wafer and attaching the second wafer to the first wafer before said separating, said separating allowing access to the electrical interconnections.

18. The method of claim 16, wherein said providing of the vertical spacer includes forming vertical spacers for each of the transceivers on a spacer wafer and attaching the spacer wafer to the first wafer before said separating, said separating allowing access to the electrical interconnections.

19. The method of claim 18, wherein said providing of the optics block includes forming the at least one optical element for each of the plurality of detectors and each of the plurality of light sources on a second wafer and attaching the second wafer to the spacer wafer and the first wafer before said separating, said separating allowing access to the electrical interconnections.

20. The method of claim 19, wherein said attaching includes directly attaching the second wafer to the spacer wafer.

21. The method of claim 16, wherein said providing of one of said plurality of light sources and said plurality of detectors includes monolithically integrating into the first wafer.

22. The method of claim 16, wherein said providing electrical interconnections for each of the plurality of detectors and each of the plurality of light sources includes using a same mask for both interconnections to the detectors and the light sources.