GB2054949A - Cooling arrangement for laser diode - Google Patents

Cooling arrangement for laser diode Download PDF

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Publication number
GB2054949A
GB2054949A GB7926127A GB7926127A GB2054949A GB 2054949 A GB2054949 A GB 2054949A GB 7926127 A GB7926127 A GB 7926127A GB 7926127 A GB7926127 A GB 7926127A GB 2054949 A GB2054949 A GB 2054949A
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GB
United Kingdom
Prior art keywords
laser diode
circuit
current
diode
laser
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Granted
Application number
GB7926127A
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GB2054949B (en
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STC PLC
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Standard Telephone and Cables PLC
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Publication date
Application filed by Standard Telephone and Cables PLC filed Critical Standard Telephone and Cables PLC
Priority to GB7926127A priority Critical patent/GB2054949B/en
Publication of GB2054949A publication Critical patent/GB2054949A/en
Application granted granted Critical
Publication of GB2054949B publication Critical patent/GB2054949B/en
Expired legal-status Critical Current

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Classifications

    • 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
    • H01S5/024—Arrangements for thermal management
    • H01S5/02407—Active cooling, e.g. the laser temperature is controlled by a thermo-electric cooler or water cooling
    • H01S5/02415—Active cooling, e.g. the laser temperature is controlled by a thermo-electric cooler or water cooling by using a thermo-electric cooler [TEC], e.g. Peltier element

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  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Optics & Photonics (AREA)
  • Cooling Or The Like Of Semiconductors Or Solid State Devices (AREA)
  • Semiconductor Lasers (AREA)

Abstract

A laser diode cooling circuit utilises a thermoelectric cooling arrangement TC in series connection with the laser diode LD. A monitor and feedback controlling modulator circuit which includes a monitor photo-diode MP and a transistor amplifier TR2 controls the output of the laser diode. Power which otherwise would have been dissipated as heat in the circuit is used to drive the cooler TC. Therefore the laser diode LD, so cooled, can be operated at higher ambient temperatures than previously possible. The circuit is also useful when electrical power supplies and thermal heat dissipation capabilities are restricted. <IMAGE>

Description

SPECIFICATION Cooling arrangement for laser diode This invention relates to laser diodes circuits and to cooling arrangements therefor.
Laser circuits which use thermoelectric devices to cool laser diodes are known: they require extra electrical power to run the thermoelectric device.
The present invention has as its object the provision of a circuit in which such cooling does not increase power consumption.
According to the present invention there is provided a laser diode circuit, which includes a thermoelectric cooling arrangement for the laser diode which is connected in series with the laser diode, so that current flowing in the laser diode also flows in the thermoelectric cooling arrangement.
The power which would otherwise have been dissipated as heat, is used to drive a thermoelectric cooler in series to a laser diode.
The laser diode can therefore operate in higher ambient temperatures than would otherwise have been possible.
An embodiment of the invention will now be described with reference to the accompanying drawing in which Fig. 1 shows as much of a laser modulator circuit embodying the invention as is needed to understand the invention, while Fig. 2 is a current sink circuit usuable in the arrangement of Fig. 1.
A modulated input to the circuit shown in Fig. 1 is provided by a current source (not shown) connected to the input MI and applied to the baseof a transistor TR2. The current flowing through a laser diode LD is controlled by the modulated current applied via input Ml and transistor TR2, less the current flowing through a control transistor TR 1.
Light is emitted by the laser diode LD and is transmitted down a communications link such as an optical fibre transmission line (not shown). The type of laser used emits light from its back as well as from its front, the light from its front being applied to the line. The back emitted light is applied to a photo-diode MP, so that the instantaneous emitted light power is monitored by that photo-diode MP, and the current thus produced by the photo-diode MP is subtracted from the incoming modulated input current, the resulting current being amplified by the transistor TR2. This subtraction occurs by virtue of the voltages dropped across resistor R2.
The laser diode LD receives the modified current from the transistor TR2 less the current flowing through the control transistor TR1. The circuit including the control transistorTR1 is adjustable to alter the amount of current passing though the laser diode LD, by a thermoelectric cooling device, which could be a thermistor, TC and a current sink CS connected in series to the laser diode. A possible current sink configuration is shown in Fig. 2, point X being connected to the thermoelectric cooler TC.
The circuit is usually required to operate from standard power supply voltage levels, the lowest of which is frequently 5V. Laser diodes operate with a forward bias of about 2V and less than 1 volt is required to operate a current sink. Therefore about 2 volts remain to be dropped. This power, which otherwise would have been dissipated as heat in the current sink, is supplied to the thermoelectric cooler.
When the ambient temperature falls so does the resistance of the thermoelectric cooler, so that less power is taken by the cooler and the laser diode is subjected to little additional cooling when the ambient temperature is low. In high ambient temperatures the thermoelectric cooler reduces the maximum temperature experienced by the laser diode so enabling its use in such conditions.
This invention has the advantage that the laser diode can be used in hot working conditions and the means for cooling the laser diode is powered by electrical energy which would otherwise have been lost. The configuration is therefore valuable when electrical power availability or overall thermal dissipation capability are restricted, but when the operation of a laser diode at ambient temperatures higher than the diodes maximum working temperature is required.
1. A laser diode circuit, which includes a thermoelectric cooling arrangement for the laser diode which is connected in series with the laser diode, so that current flowing in the laser diode also flows in the thermoelectric cooling arrangement.
2. A laser diode circuit as claimed in claim 1 wherein the thermoelectric cooling arrangement includes a thermistor.
3. A laser diode circuit as claimed in claim 1 or 2 wherein the current flowing though the laser diode is controlled by a transistor.
4. A laser diode circuit as claimed in claim 1, 2 or 3 wherein the thermoelectric cooling arrangement is connected in series to a current sink circuit.
5. A laser diode modulation circuit which includes a thermoelectric cooling arrangement for the diode which is connected in series with the laser diode, so that current flowing in the laser diode also flows in the thermoelectric cooling arrangement, a modulation input connected to the input of a transistor amplifier whose output stage is connected across the laser diode so as to be in series with the cooling arrangement, and a photodiode associated with the laser diode so as to receive right back ernitfedfrnm the laser diode, the current generated by the photo-diode being subtracted from the modulation input current so as to exert a regulatory influence on the modulated light output of the laser diode.
6. A laser diode modulation circuit as claimed in claim 5 wherein the thermoelectric cooling arrangement includes a thermistor.
7. A laser diode modulation circuit as claimed in claim 5 or 6 wherein the current flowing
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (11)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Cooling arrangement for laser diode This invention relates to laser diodes circuits and to cooling arrangements therefor. Laser circuits which use thermoelectric devices to cool laser diodes are known: they require extra electrical power to run the thermoelectric device. The present invention has as its object the provision of a circuit in which such cooling does not increase power consumption. According to the present invention there is provided a laser diode circuit, which includes a thermoelectric cooling arrangement for the laser diode which is connected in series with the laser diode, so that current flowing in the laser diode also flows in the thermoelectric cooling arrangement. The power which would otherwise have been dissipated as heat, is used to drive a thermoelectric cooler in series to a laser diode. The laser diode can therefore operate in higher ambient temperatures than would otherwise have been possible. An embodiment of the invention will now be described with reference to the accompanying drawing in which Fig. 1 shows as much of a laser modulator circuit embodying the invention as is needed to understand the invention, while Fig. 2 is a current sink circuit usuable in the arrangement of Fig. 1. A modulated input to the circuit shown in Fig. 1 is provided by a current source (not shown) connected to the input MI and applied to the baseof a transistor TR2. The current flowing through a laser diode LD is controlled by the modulated current applied via input Ml and transistor TR2, less the current flowing through a control transistor TR 1. Light is emitted by the laser diode LD and is transmitted down a communications link such as an optical fibre transmission line (not shown). The type of laser used emits light from its back as well as from its front, the light from its front being applied to the line. The back emitted light is applied to a photo-diode MP, so that the instantaneous emitted light power is monitored by that photo-diode MP, and the current thus produced by the photo-diode MP is subtracted from the incoming modulated input current, the resulting current being amplified by the transistor TR2. This subtraction occurs by virtue of the voltages dropped across resistor R2. The laser diode LD receives the modified current from the transistor TR2 less the current flowing through the control transistor TR1. The circuit including the control transistorTR1 is adjustable to alter the amount of current passing though the laser diode LD, by a thermoelectric cooling device, which could be a thermistor, TC and a current sink CS connected in series to the laser diode. A possible current sink configuration is shown in Fig. 2, point X being connected to the thermoelectric cooler TC. The circuit is usually required to operate from standard power supply voltage levels, the lowest of which is frequently 5V. Laser diodes operate with a forward bias of about 2V and less than 1 volt is required to operate a current sink. Therefore about 2 volts remain to be dropped. This power, which otherwise would have been dissipated as heat in the current sink, is supplied to the thermoelectric cooler. When the ambient temperature falls so does the resistance of the thermoelectric cooler, so that less power is taken by the cooler and the laser diode is subjected to little additional cooling when the ambient temperature is low. In high ambient temperatures the thermoelectric cooler reduces the maximum temperature experienced by the laser diode so enabling its use in such conditions. This invention has the advantage that the laser diode can be used in hot working conditions and the means for cooling the laser diode is powered by electrical energy which would otherwise have been lost. The configuration is therefore valuable when electrical power availability or overall thermal dissipation capability are restricted, but when the operation of a laser diode at ambient temperatures higher than the diodes maximum working temperature is required. CLAIMS
1. A laser diode circuit, which includes a thermoelectric cooling arrangement for the laser diode which is connected in series with the laser diode, so that current flowing in the laser diode also flows in the thermoelectric cooling arrangement.
2. A laser diode circuit as claimed in claim 1 wherein the thermoelectric cooling arrangement includes a thermistor.
3. A laser diode circuit as claimed in claim 1 or 2 wherein the current flowing though the laser diode is controlled by a transistor.
4. A laser diode circuit as claimed in claim 1, 2 or 3 wherein the thermoelectric cooling arrangement is connected in series to a current sink circuit.
5. A laser diode modulation circuit which includes a thermoelectric cooling arrangement for the diode which is connected in series with the laser diode, so that current flowing in the laser diode also flows in the thermoelectric cooling arrangement, a modulation input connected to the input of a transistor amplifier whose output stage is connected across the laser diode so as to be in series with the cooling arrangement, and a photodiode associated with the laser diode so as to receive right back ernitfedfrnm the laser diode, the current generated by the photo-diode being subtracted from the modulation input current so as to exert a regulatory influence on the modulated light output of the laser diode.
6. A laser diode modulation circuit as claimed in claim 5 wherein the thermoelectric cooling arrangement includes a thermistor.
7. A laser diode modulation circuit as claimed in claim 5 or 6 wherein the current flowing through the laser diode is controlled by a transistor.
8. A laser diode modulation circuit as claimed in claim 5, 6 or 7 wherein the thermoelectric cooling arrangement is connected in series to a current sink circuit.
9. A laser diode modulation circuit substantially as described herein with reference to the accompanying drawing.
New claims filed on 12 Feb 1980 New claims: Appendant claims 10 and 11 added
10. A laser diode. circuit, which includes a thermoelectric cooling arrangement for the laser diode which is connected in series with the laser diode, so that current flowing in the laser diode also flows in the thermoelectric cooling arrangement, in which a modulation current for the laser diode is applied thereto via amplification means the output of which is controlled via a monitoring circuit which monitors the laser output, and in which the current applied via the said amplification means to the laser diode is also applied to said cooling arrangement so that the current flowing therein is also dependent on the laser output.
11. A laser diode circuit as claimed in claim 10, and in which the monitoring circuit consists of a photo-diode responsive to light back-emitted from the laser diode, which photo-diode is connected in series with a resistor, the junction between the photo-diode and the resistor being connected to the input of the amplification means.
GB7926127A 1979-07-26 1979-07-26 Cooling arrangement for laser diode Expired GB2054949B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB7926127A GB2054949B (en) 1979-07-26 1979-07-26 Cooling arrangement for laser diode

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB7926127A GB2054949B (en) 1979-07-26 1979-07-26 Cooling arrangement for laser diode

Publications (2)

Publication Number Publication Date
GB2054949A true GB2054949A (en) 1981-02-18
GB2054949B GB2054949B (en) 1983-04-07

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Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2526237A1 (en) * 1982-04-30 1983-11-04 Cit Alcatel DEVICE FOR THERMAL CONTROL OF A SEMICONDUCTOR LASER
GB2131607A (en) * 1982-11-24 1984-06-20 Hitachi Ltd Semiconductor laser device
WO1984003592A1 (en) * 1983-03-09 1984-09-13 Pierre Lecoy Method and device for regulating the light power of laser diodes
DE3603548A1 (en) * 1985-02-19 1986-10-02 Videoton Elektronikai Vállalat, Székesfehérvár Method for determining and regulating the temperature of laser diodes, and a circuit arrangement for carrying out the method
GB2180985A (en) * 1985-09-28 1987-04-08 Int Standard Electric Corp Laser device with stabilised power output
GB2190783A (en) * 1986-05-13 1987-11-25 Litton Systems Inc Laser diode intensity and wavelength control
US4842358A (en) * 1987-02-20 1989-06-27 Litton Systems, Inc. Apparatus and method for optical signal source stabilization
US4856011A (en) * 1985-01-30 1989-08-08 Ricoh Company, Ltd. Semiconductor laser control circuit
US5012325A (en) * 1990-04-24 1991-04-30 International Business Machines Corp. Thermoelectric cooling via electrical connections
US5032897A (en) * 1990-02-28 1991-07-16 International Business Machines Corp. Integrated thermoelectric cooling
EP1182757A2 (en) * 2000-07-26 2002-02-27 Robert Bosch Gmbh Laserdiode assembly

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2526237A1 (en) * 1982-04-30 1983-11-04 Cit Alcatel DEVICE FOR THERMAL CONTROL OF A SEMICONDUCTOR LASER
EP0093942A1 (en) * 1982-04-30 1983-11-16 Alcatel Semiconductor laser cooling device
GB2131607A (en) * 1982-11-24 1984-06-20 Hitachi Ltd Semiconductor laser device
US4604753A (en) * 1982-11-24 1986-08-05 Hitachi, Ltd. Semiconductor laser module having an improved temperature control arrangement
WO1984003592A1 (en) * 1983-03-09 1984-09-13 Pierre Lecoy Method and device for regulating the light power of laser diodes
FR2542511A1 (en) * 1983-03-09 1984-09-14 Lecoy Pierre METHOD AND DEVICE FOR REGULATING THE LIGHT POWER OF LASER DIODES
US4856011A (en) * 1985-01-30 1989-08-08 Ricoh Company, Ltd. Semiconductor laser control circuit
DE3603548A1 (en) * 1985-02-19 1986-10-02 Videoton Elektronikai Vállalat, Székesfehérvár Method for determining and regulating the temperature of laser diodes, and a circuit arrangement for carrying out the method
GB2180985A (en) * 1985-09-28 1987-04-08 Int Standard Electric Corp Laser device with stabilised power output
AU586279B2 (en) * 1985-09-28 1989-07-06 Alcatel N.V. Laser device
GB2180985B (en) * 1985-09-28 1989-10-25 Int Standard Electric Corp Laser device with stabilised power output
GB2190783A (en) * 1986-05-13 1987-11-25 Litton Systems Inc Laser diode intensity and wavelength control
US4792956A (en) * 1986-05-13 1988-12-20 Litton Systems, Inc. Laser diode intensity and wavelength control
GB2190783B (en) * 1986-05-13 1989-12-13 Litton Systems Inc Laser diode intensity and wavelength control
US4842358A (en) * 1987-02-20 1989-06-27 Litton Systems, Inc. Apparatus and method for optical signal source stabilization
US5032897A (en) * 1990-02-28 1991-07-16 International Business Machines Corp. Integrated thermoelectric cooling
US5012325A (en) * 1990-04-24 1991-04-30 International Business Machines Corp. Thermoelectric cooling via electrical connections
EP1182757A2 (en) * 2000-07-26 2002-02-27 Robert Bosch Gmbh Laserdiode assembly
EP1182757A3 (en) * 2000-07-26 2003-01-15 Tesat-Spacecom GmbH & Co. KG Laserdiode assembly

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Publication number Publication date
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Legal Events

Date Code Title Description
746 Register noted 'licences of right' (sect. 46/1977)
PCNP Patent ceased through non-payment of renewal fee