WO2013079941A1 - Laser pumping system - Google Patents

Laser pumping system Download PDF

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Publication number
WO2013079941A1
WO2013079941A1 PCT/GB2012/052943 GB2012052943W WO2013079941A1 WO 2013079941 A1 WO2013079941 A1 WO 2013079941A1 GB 2012052943 W GB2012052943 W GB 2012052943W WO 2013079941 A1 WO2013079941 A1 WO 2013079941A1
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Prior art keywords
wavelength
pumping system
emitters
laser
radiation source
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PCT/GB2012/052943
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French (fr)
Inventor
Trevor Cook
Stephen Lee
William Alexander
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Thales Holdings Uk Plc
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Application filed by Thales Holdings Uk Plc filed Critical Thales Holdings Uk Plc
Priority to EP12810405.6A priority Critical patent/EP2786455A1/en
Publication of WO2013079941A1 publication Critical patent/WO2013079941A1/en

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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
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
    • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
    • H01S3/094096—Multi-wavelength pumping
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/15—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components with at least one potential-jump barrier or surface barrier specially adapted for light emission
    • 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
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/02—Constructional details
    • H01S3/04—Arrangements for thermal management
    • H01S3/042—Arrangements for thermal management for solid state lasers
    • 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
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
    • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
    • H01S3/094038—End pumping
    • 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
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • 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
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/13—Stabilisation of laser output parameters, e.g. frequency or amplitude
    • 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
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/13—Stabilisation of laser output parameters, e.g. frequency or amplitude
    • H01S3/131—Stabilisation of laser output parameters, e.g. frequency or amplitude by controlling the active medium, e.g. by controlling the processes or apparatus for excitation
    • H01S3/1312—Stabilisation of laser output parameters, e.g. frequency or amplitude by controlling the active medium, e.g. by controlling the processes or apparatus for excitation by controlling the optical pumping
    • 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
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/14—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range characterised by the material used as the active medium
    • H01S3/16—Solid materials
    • 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
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/14—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range characterised by the material used as the active medium
    • H01S3/16—Solid materials
    • H01S3/163—Solid materials characterised by a crystal matrix
    • H01S3/164—Solid materials characterised by a crystal matrix garnet
    • H01S3/1643—YAG
    • 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
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
    • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
    • H01S3/0941—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light of a laser diode
    • 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
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/102—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling the active medium, e.g. by controlling the processes or apparatus for excitation
    • H01S3/1022—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling the active medium, e.g. by controlling the processes or apparatus for excitation by controlling the optical pumping
    • 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
    • H01S5/06804—Stabilisation of laser output parameters by monitoring an external parameter, e.g. temperature
    • 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
    • H01S5/0687—Stabilising the frequency of the laser
    • 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
    • H01S5/40—Arrangement of two or more semiconductor lasers, not provided for in groups H01S5/02 - H01S5/30
    • H01S5/4025—Array arrangements, e.g. constituted by discrete laser diodes or laser bar
    • H01S5/4087—Array arrangements, e.g. constituted by discrete laser diodes or laser bar emitting more than one wavelength

Abstract

The invention relates to a pumping system (5) for pumping a gain medium of a laser, the pumping system (5) comprising a radiation source, the radiation source comprising a plurality of emitters (10a, 10b, 10c, 10d, 10e), wherein at least one of the emitters is configured to produce radiation having a different wavelength or a different band of wavelengths to at least one other of the emitters at a given temperature.

Description

Laser Pumping System
The present invention relates to a pumping system for lasers, and particularly but not exclusively to a pumping mechanism for lasers that comprise gain material having a narrow absorption band.
Background
Lasing or gain materials are available that have favourable properties such as high gain and good robustness, but have narrow absorption bands. An example of such a material is Nd:YAG, which has an absorption band with a spectral width of approximately 8nm. The narrowness of the absorption band is not so much of an issue in systems that use a broadband light source. However, such systems are generally less efficient, since the light source produces radiation over a wide spectrum and therefore a significant proportion of the radiation produced by the light source lies outwith the absorption band of the lasing material and therefore does not result in pumping of the lasing material.
Narrow band light sources such as laser diodes can be advantageously used to increase the efficiency of a laser by producing energy at a wavelength that can be matched to the absorption band of the gain medium of the laser. However, many such narrow band light sources, particularly diode based light sources, suffer from wavelength drift, wherein the wavelength produced by the light source varies with temperature. For example, in some laser diode systems, the wavelength can vary at approximately 0.3nrn/°C. In applications that require use of the laser over a wide range of ambient temperatures, this drift can be enough to cause the light produced by the light source to drift out of the absorption band of the pumping material, and thereby significantly impairing the output of the laser. Some solutions to this problem already exist. For example, temperature controlled diodes may be used. However, such solutions generally result in reduced efficiency, for example due to energy used to control the temperature, which is a disadvantage in systems where power is limited, such as battery powered systems, or where a reduction in power consumption of the apparatus would be beneficial. It is at least one object of at least one embodiment of the present invention to provide an improved laser pumping system and associated laser, for example, a system having an improved efficiency and being operable over a wide temperature range. Statements of Invention
According to a first aspect of the present invention is a pumping system for pumping a gain medium of a laser, the pumping system comprising a radiation source, the radiation source comprising a plurality of emitters, wherein at least one of the emitters is configured to produce radiation having a different wavelength or a different band of wavelengths to at least one other of the emitters at a given temperature.
The emitters may be selectively and/or individually activatable. The pumping system may be configured to selectively activate emitters according to an output of at least one sensor for sensing at least one parameter of the pumping system. The sensor(s) may comprise a temperature sensor and/or an optical sensor, or the like. The parameters) of the pumping system may comprise a temperature of the radiation source and/or a wavelength of the radiation output by the radiation source, or the like. The pumping system may be configured to activate selected emitters depending on the parameters) determined using the sensor in order to maintain the wavelength of radiation output by the radiation source at one or more required or desired wavelengths and/or within a required or desired band of wavelengths.
The pumping system may comprise a controller that is operable to control the radiation source to maintain the wavelength of the radiation at the one or more required or desired wavelengths or within the required or desired wavelength band.
According to a second aspect of the present invention is a pumping system for pumping a gain medium of a laser, the pumping system comprising a radiation source, wherein the wavelength of the radiation produced by the radiation source is controllable, and a controller that is operable to control the radiation source to maintain the wavelength of the radiation at one or more desired or required wavelengths or within one or more wavelength bands. The radiation source may comprise a plurality of emitters. At least one and preferably each of the emitters may be configured to produce radiation having a different wavelength or in a different band of wavelengths to at least one other of the emitters at a given temperature.
The radiation source may comprise a light source and the radiation may comprise light. The plurality of emitters may comprise light emitters. At least one and preferably each emitter may comprise one or optionally more diode based light emitters, which may preferably comprise laser diodes but may optionally comprise LEDs or the like. The pumping system may comprise an optical pumping system.
The emitters may be individually addressable by the controller. The controller may be configured to activate and/or deactivate selected emitters. The controller may comprise or be configured to operate a multi channel electrical supply for selectively controlling power supplied to the emitters, for example, the controller may be configured to selectively fade or switch power from one emitter to another.
The pumping system may comprise at least one sensor, such as a temperature sensor and/or a radiation detector, or the like. The sensor(s) may be configured to determine or monitor at least one parameter of the pumping system. The parameter(s) of the system may comprise radiation emitted by the radiation source, the temperature of the radiation source, or the like
The controller may be configured to control the operation of selected emitters dependent on the parameters) of the pumping system monitored or determined using the sensor, for example by activating and/or deactivating selected emitters dependant on the determined or monitored parameter.
For example, in the case of a temperature sensor, the controller may be configured to control the operation of selected emitters dependent on the temperature of the radiation source determined using the at least one temperature sensor.
The controller may be configured to maintain the wavelength of the radiation at the required or desired wavelength or within the required or desired wavelength band by selectively activating emitters that emit radiation having or comprising the required or desired wavelength or having or comprising a wavelength that is within the required or desired wavelength band at the determined parameter value (e.g. temperature). The required or desired wavelength or wavelength band may comprise 808nm. For example, the controller may be provided with, or configured to access, correspondence data, such as a look-up table, calibration data, a function or curve or the like. The correspondence data may relate the parameter, e.g. temperature of the radiation source, to the wavelength of radiation emitted by each of the emitters. The correspondence data may indicate and/or or be usable to determine which emitter is to be activated for a given parameter value. The controller may be configured to selectively control operation of the emitters in order to maintain the output of the radiation source at the desired or required wavelength and/or within the required or desired wavelength band, for example, by selectively activating one or more emitters associated with the determined parameter value, as derived from the correspondence data. The required or desired wavelength and/or required or desired wavelength band may correspond to the absorption wavelength or band of a laser gain medium.
By way of a particular example, the radiation source may comprise a stack formed from a plurality of laser diodes, each laser diode producing a different wavelength (or colour) at a given temperature. The change in the wavelength of light output by each laser diode with temperature may be known and may be stored or accessible by the controller. In this way, the controller may be configured to monitor the temperature of the laser diode stack and determine which laser diode would produce light having a required or optimal wavelength, which may comprise a wavelength closest to an optimal absorption wavelength of the lasing medium for the determined temperature, and selectively activate the laser diode whose output is determined to have a closest match to the required or optimal wavelength and deactivate the rest of the laser diodes. Optionally, if the required or optimal wavelength lies between the wavelengths of two laser diodes, then power can be faded between the two laser diodes having neighbouring wavelengths, for example, depending on the determined temperature.
Activation of the emitter may comprise providing it with a pump current pulse, which may be greater than the turn on current of the emitter. Deactivation of an emitter may comprise providing it with current at or proximate the turn on current for the emitter. As an alternate embodiment or additional feature, the controller may be configured to determine a wavelength or wavelength band output by the radiation source using the radiation detector(s). The controller may be configured to selectively control the operation of one or more emitters based on the output wavelength or wavelength band of the radiation source determined using the radiation detector(s). The controller may be configured to selectively activate, fade or switch to an emitter having an output with a higher wavelength than a currently or previously active emitter if the wavelength of the output of the pumping system decreases, for example, from the required or desired wavelength or wavelength band, e.g. below a threshold, and/or selectively activate, fade or switch to an emitter having an output of lower wavelength than the currently or previously active emitter if the wavelength of the output of the pumping system increases, for example, from the required or desired wavelength or wavelength band, e.g. above a threshold. In this way, it may be possible to produce a radiation source for pumping the gain medium of a laser that provides the energy and pumping efficiency of a narrowband radiation source with the stability and robustness to temperature variation associated with a broadband light source. According to a third aspect of the present invention is a laser comprising a gain medium and a pumping system according to the first and/or second aspect, wherein the pumping system is configured or operable to pump or excite the gain medium.
The gain medium may comprise Nd:YAG.
The pumping system may be configured to controllably output radiation of a required or desired wavelength. The required or desired wavelength may comprise an absorption wavelength of the gain medium and/or lie within an absorption band of the gain medium. The pumping system may be configured to output radiation having a wavelength of 808nm, and/or a wavelength band between 800nm and 816nm.
The pumping system may be configured to selectively activate one or optionally more emitters having different output wavelengths in order to maintain the wavelength of the output of the pumping system at the absorption wavelength and/or within the absorption band of the gain medium. The laser may comprise an end pumped laser. In end pumped lasers, the absorption length may vary considerably with the wavelength of radiation output by the pumping system. By providing a pumping system as described above in an end pumped laser configuration, the absorption length may be efficiently kept constant.
According to a fourth aspect of the present invention is a method of pumping a gain medium of a laser, the method comprising controlling a radiation source to maintain the wavelength of the radiation produced by the radiation source to a required or desired wavelength or wavelength band.
The required or desired wavelength or wavelength band may comprise an absorption wavelength or an absorption wavelength band of the gain medium. The method may comprise use of a pumping system of the first and/or second aspect and/or a system of the third aspect.
It will be appreciated that features analogous to those described in relation to any of the above aspects may be applicable to any of the other aspects,
Method features corresponding to use of any features described above in relation to apparatus and/or apparatus features configured to implement any features described above in relation to a method are also contemplated as falling within the scope of the present invention.
Brief Description of the Drawings
The invention will be described herein with respect to the following drawings: Figure 1 shows an optical pumping system for a laser; and Figure 2 shows another optical pumping system for a laser.
Detailed Description of the Drawings Figure 1 shows a pumping system 5 comprising a plurality of light emitters 10a, 10b, 10c, 10d, 10e (in this case five emitters) in a stack 12, each emitter 10a-10e comprising a laser diode. Each emitter 10a-10e is configured to produce light at a different wavelength to each of the other emitters 10a-10e when operated at the same temperature. Each emitter 10a-10e is provided with a corresponding drive unit 15a- 15e for providing and controlling power to each emitter 10a-10e. Each drive unit 15a- 15e is fed with power from a high current power supply 20. The drive units 15a-15e are operable under the control of a controller 25 such that the power supplied to each emitter 10a-10e is individually and selectively controlled.
The laser diode stack 2 is provided with a sensor 30a, 30b. In the embodiment shown in Figure 1 , the sensor is a temperature sensor 30a for monitoring the temperature of the stack 12. The controller 25 is operable to control which emitters 10a-10e are activated to output light dependent on the measurement obtained from the sensor 30a, 30b by controlling the power supplied to each emitter 10a-10e using the associated drive units 15a-15e.
The pumping system 5 can be incorporated into a laser (not shown) in order to optically pump a gain or lasing medium. The gain medium of the laser has an optimal absorption wavelength and/or absorption band. The output of the laser diodes that are comprised in each emitter 10a-10e varies with temperature. The control unit 25 receives temperature data from the sensor 30a and is operable to use calibration data such as a look up table to determine which emitter 10a-10e would produce radiation within the absorption band or closest to the optimal wavelength of the gain medium at the temperature sensed by the temperature sensor 30a. The control unit 25 then activates the determined emitter 10a-10e by operating the corresponding drive unit 15a-15e to provide it with a current pulse of sufficient magnitude to produce an optical output required to pump the gain medium. The other emitters 10a-10e are provided with turn on current only.
If the controller 25 determines that the required wavelength lies between the wavelength produced by two of the emitters 0a-10e or that more than one emitter 10a-10e will produce light in the wavelength band, then the controller 25 is optionally operable to fade power between the emitters 10a-10e having neighbouring wavelengths such that a proportion of the pump current is split between each emitter 10a-10e but enough to elevate the current supplied above the turn-on current threshold.
Controlling the active emitters 10a-10e based on a temperature measurement of the diode stack 12 may advantageously provide a low cost and simple implementation of the present invention. However, it will be appreciated that the present invention need not rely on temperature sensing.
Another embodiment of a pumping system 5' is illustrated in Fig. 2. In this system 5', components corresponding to those illustrated in Fig. 1 are given corresponding references. However, instead of a temperature sensor 30a, an optical sensor 30b is provided for monitoring the spectral output of the pumping system 5'. For example, the optical sensor 30b may comprise suitable optical sensing apparatus such as a CMOS or CCD optical detector array, spectrometer device or the like.
In this case, the control unit 25' is configured to directly monitor the spectral output of the pumping system 5' using the optical sensor 30b. The control unit 25' is configured to directly determine the wavelength of light produced by the pumping system 5' and determine if it deviates from the wavelength or wavelength band required for optimal pumping of the gain medium of the laser. In this case, if the wavelength increases or decreases by a predetermined amount, the control unit 25' can switch or fade an active emitter 10a-10e to an emitter 10a-10e having a lower or higher wavelength output respectively in order to maintain the output of the pumping system 5' within the required wavelength band.
In a preferred embodiment, the laser system comprises an end pumped laser that uses Nd:YAG as the gain medium. In this case, the useful absorption band of the gain medium is around 808nm ± 4nm. For end pumped configurations, the absorption depth varies considerably with the wavelength of the pumping radiation and therefore, variations in the spectral output of the pumping system can result in particularly severe variations in the thermal conditions of the gain medium.
It will be appreciated that although advantageous examples of the invention are described above, variations to the above example are contemplated. For example, it will appreciated that the present invention is operable with a wide variety of suitable gain medium materials, laser configurations and resonant cavity configurations known in the art, with varying degrees of efficacy, and is not limited to any particular configuration or material.
In addition, although the above examples describe pumping systems that advantageously comprise a stack of light emitters in the form of laser diodes, it will be appreciated that other light emitters may be used. Preferably the emitters comprise diode based emitters such as LEDs or the like, but the emitters are not limited to diode based emitters and the invention is also intended to cover the use of non-diode based emitters.
Furthermore, although the above examples describe controlling the wavelength of the light output by the pumping system to correspond with a maximum absorption wavelength or wavelength band of the gain medium of the laser, it will be appreciated that this need not necessarily always be the case. Instead, the wavelength or wavelength band of the pumping system may be controllable or selectable or configured to output radiation having one or more required or desired wavelengths or wavelength bands that may or may not correspond to the maximum absorption wavelength or wavelength band of the gain medium of the laser. For example, in some situations it may be preferable to de-tune the laser or selectively deactivate the laser or de-optimise the absorption, e.g. to increase the absorption length and spread out the heat load. Therefore, it will be appreciated that the present invention is not limited to the situation where the output of the pumping system is controlled to be at or within the maximum absorption wavelength or wavelength band of the gain medium of the laser.
Additionally, although a specific example is given above in which the sensor is a temperature sensor and the system parameter to which the pump system is controlled (i.e. the parameter used to determine which emitter(s) should be activated) is the temperature of the emitters. Another specific example is given in which the sensor is an optical sensor and the system parameter to which the pump system is controlled is the wavelength of the light output by the pumping system. However, it will be appreciated that other sensors and/or other system parameters may be used. For example, a sensor could be provided that is configured to determine non-absorbed pump through the gain medium and/or fluorescence from the gain medium (e.g. as an indicator of stored energy) and control the pump system accordingly. Therefore, it will be appreciated that the present invention is not limited to temperature or optical sensors or to control the system based on system parameters that comprise temperature or wavelength but that other sensors or control data could be used, as would be apparent to a skilled person from the teachings of the present specification.
Therefore, it will be appreciated that the above specific description is provided by way of example only and that the scope of the invention is defined by the claims and not limited to the specific examples described in the detailed description of the drawings.

Claims

Claims
1. A pumping system for pumping a gain medium of a laser, the pumping system comprising a radiation source, the radiation source comprising a plurality of emitters, wherein at least one of the emitters is configured to produce radiation having a different wavelength or a different band of wavelengths to at least one other of the emitters at a given temperature.
2. The pumping system as claimed by claim 1 , wherein the emitters are selectively and individually activatable.
3. The pumping system as claimed in claim 1 or claim 2, wherein the pumping system is configured to selectively activate emitters according to an output of a sensor for sensing a parameter of the pumping system.
4. The pumping system according to claim 3, wherein the sensor comprises a temperature sensor and/or an optical sensor.
5. The pumping system according to claim 4, wherein the pumping system is configured to activate selected emitters depending on the parameter determined using the sensor in order to maintain the wavelength of radiation output by the radiation source at a required wavelength and/or within a required band of wavelengths.
6. A pumping system for pumping a gain medium of a laser, the pumping system comprising a radiation source, wherein the wavelength of the radiation produced by the radiation source is controllable, and a controller that is operable to control the radiation source to maintain the wavelength of the radiation at a desired wavelength or within wavelength band.
7. The pumping system of claim 6, wherein the radiation source comprises a plurality of emitters, wherein at least one of the emitters is configured to produce radiation having a different wavelength or in a different band of wavelengths to at least one other of the emitters at a given temperature.
8. The pumping system according to any preceding claim, wherein at least one emitter comprises one or more laser diodes.
9. The pumping system according to any of claims 6 to 8, wherein the emitters are individually addressable by the controller and the controller is configured to activate and/or deactivate selected emitters.
10. The pumping system according to any of claims 6 to 9, wherein the pumping system comprises at least one sensor for determining and/or monitoring at least one parameter of the system.
11. The pumping system according to any of claims 6 to 10, wherein the controller is configured to control the operation of selected emitters dependent on the at least one parameter of the system determined using the at least one sensor.
12. The pumping system according to any of claims 6 to 11 , wherein the controller is provided with, or configured to access, correspondence data, the correspondence data indicating or being usable to determine which emitter is to be activated for a given parameter value.
13. The pumping system according to claim 12, wherein the controller is configured to selectively control operation of the emitters in order to maintain the output of the radiation source at a required wavelength and/or within a required wavelength band by selectively activating one or more emitters associated with the determined parameter value derived from the correspondence data.
14. The pumping system according to claim 13, wherein the required wavelength and/or required wavelength band corresponds to the absorption wavelength or band of a laser gain medium.
15. The pumping system according to claim 11 or any claim dependent thereon, wherein controlling the operation of selected emitters comprises providing a selected emitter with a pump current pulse that is greater than the turn on current of the emitter and providing at least one other emitter with a current at the turn on current for the emitter.
16. The pumping system according to any of claims 10 to 15, wherein the sensor comprises a temperature sensor for monitoring the temperature of the radiation source and/or a radiation detector for monitoring the radiation emitted by the radiation source; and the controller is configured to determine a temperature of the radiation source using the temperature sensor(s) and/or a wavelength or wavelength band output by the radiation source using the radiation detector(s) and selectively control the operation of one or more emitters based on the determined temperature and/or wavelength or wavelength band output by the radiation source.
17. The pumping system according to claim 16, wherein the controller is configured to selectively activate, fade or switch to an emitter having an output with a higher wavelength than a currently or previously active emitter if the wavelength of the output of the pumping system decreases and/or selectively activate, fade or switch to an emitter having an output of lower wavelength than the currently or previously active emitter if the wavelength of the output of the pumping system increases.
18. A laser comprising a gain medium and a pumping system according to any of claims 1 to 17, wherein the pumping system is configured or operable to pump or excite the gain medium.
19. The laser according to claim 18, wherein the gain medium comprises Nd:YAG.
20. The laser according to claim 18 or claim 19, wherein the pumping system is configured to controllably output radiation of a selected wavelength, wherein the selected wavelength comprises an absorption wavelength of the gain medium and/or lies within an absorption band of the gain medium.
21. The laser according to any of claims 18 to 20, wherein the laser comprises an end pumped laser.
22. A method of pumping a gain medium of a laser, the method comprising controlling a radiation source to maintain the wavelength of the radiation produced by the radiation source to an absorption wavelength or within an absorption wavelength band of a laser.
23. The method of claim 22 comprising use of a pumping system according to any of claims 1 to 17 and/or a laser according to any of claims 18 to 21.
24. A pumping system as shown herein in the drawings and/or as described herein in relation to the drawings.
PCT/GB2012/052943 2011-11-30 2012-11-29 Laser pumping system WO2013079941A1 (en)

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Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4942587A (en) * 1988-03-10 1990-07-17 Brother Kogyo Kabushiki Kaisha Optically pumped solid-state laser oscillator
EP0390525A2 (en) * 1989-03-28 1990-10-03 Sharp Kabushiki Kaisha An optical pumping-type solid-state laser apparatus with a semiconductor laser device
EP0469568A1 (en) * 1990-07-30 1992-02-05 Sony Corporation End pumped solid-state laser
US5926495A (en) * 1997-08-04 1999-07-20 Litton Systems, Inc. Laser diode pump wavelength sensing and control apparatus and method
US5930030A (en) * 1996-01-19 1999-07-27 Sdl, Inc. Apparatus for pumping an optical gain medium with multiple light wavelengths
EP1324440A2 (en) * 2001-12-28 2003-07-02 Communications Research Laboratory, Independent Administrative Institution Diode-pumped solid-state laser oscillator
US20090097507A1 (en) * 2007-10-15 2009-04-16 Pavilion Integration Corporation Wavelength and Intensity Stabilized Laser Diode and Application of Same to Pumping Solid-State Lasers
US20110150026A1 (en) * 2009-12-18 2011-06-23 Inter-University Research Institute Corporation, National Institutes Of Natural Sciences Semiconductor laser pumped solid-state laser device for engine ignition

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4901330A (en) * 1988-07-20 1990-02-13 Amoco Corporation Optically pumped laser
US7826509B2 (en) * 2006-12-15 2010-11-02 President And Fellows Of Harvard College Broadly tunable single-mode quantum cascade laser sources and sensors
US8428091B2 (en) * 2009-12-21 2013-04-23 Electronics And Telecommunications Research Institute Tunable laser module

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4942587A (en) * 1988-03-10 1990-07-17 Brother Kogyo Kabushiki Kaisha Optically pumped solid-state laser oscillator
EP0390525A2 (en) * 1989-03-28 1990-10-03 Sharp Kabushiki Kaisha An optical pumping-type solid-state laser apparatus with a semiconductor laser device
EP0469568A1 (en) * 1990-07-30 1992-02-05 Sony Corporation End pumped solid-state laser
US5930030A (en) * 1996-01-19 1999-07-27 Sdl, Inc. Apparatus for pumping an optical gain medium with multiple light wavelengths
US5926495A (en) * 1997-08-04 1999-07-20 Litton Systems, Inc. Laser diode pump wavelength sensing and control apparatus and method
EP1324440A2 (en) * 2001-12-28 2003-07-02 Communications Research Laboratory, Independent Administrative Institution Diode-pumped solid-state laser oscillator
US20090097507A1 (en) * 2007-10-15 2009-04-16 Pavilion Integration Corporation Wavelength and Intensity Stabilized Laser Diode and Application of Same to Pumping Solid-State Lasers
US20110150026A1 (en) * 2009-12-18 2011-06-23 Inter-University Research Institute Corporation, National Institutes Of Natural Sciences Semiconductor laser pumped solid-state laser device for engine ignition

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EP2786455A1 (en) 2014-10-08
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GB2497107A (en) 2013-06-05
GB2497107B (en) 2014-01-08

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