Thermal compensation in semiconductor lasers

• US 20080063016A1
• Filed: 09/13/2006
• Published: 03/13/2008
• Est. Priority Date: 09/13/2006
• Status: Abandoned Application

• Current Assignee: Corning Incorporated
• Original Assignee: Corning Incorporated
• Inventors: Bhatia, Vikram, Ricketts, Daniel Ohen, Loeber, David August Sniezek, Zah, Chung-En, Hu, Martin Hai, Liu, Xingsheng
• Application Number:
  US11/520,223
• Publication Number:
  US 20080063016A1
• Time in Patent Office: Days
• US Class Current: 372/34
• CPC Class Codes: H01S 5/024 Arrangements for thermal management
• CPC Class Codes: H01S 5/02453 Heating, e.g. the laser is heated for stabilisation against temperature fluctuations of the environment H01S5/0612 takes precedence, for monolithically integrated heaters see also H01S5/0261
• CPC Class Codes: H01S 5/0261 Non-optical elements, e.g. laser driver components, heaters H01S5/0265 takes precedence
• CPC Class Codes: H01S 5/04256 characterised by the configuration
• CPC Class Codes: H01S 5/0612 controlled by temperature
• CPC Class Codes: H01S 5/06213 Amplitude modulation
• CPC Class Codes: H01S 5/06251 Amplitude modulation
• CPC Class Codes: H01S 5/06256 with DBR-structure
• CPC Class Codes: H01S 5/22 having a ridge or stripe structure
• CPC Class Codes: H01S 5/2231 with inner confining structure only between the active layer and the upper electrode

Abstract

The present invention relates to methods for modulating a semiconductor laser and wavelength matching to a wavelength converter using monolithic micro-heaters integrated in the semiconductor laser. The present invention also relates to wavelength matching and stabilization in laser sources in general, without regard to whether the laser is modulated or whether second harmonic generation is utilized in the laser source. According to one embodiment of the present invention, a method of compensating for thermally induced patterning effects in a semiconductor laser is provided where the laser'"'"'s heating element driving current I_H is set to a relatively high magnitude when the laser'"'"'s driving current I_D is at a relatively low magnitude. Additional embodiments are disclosed and claimed.

Claims

1. A method of compensating for thermally induced patterning effects in a semiconductor laser, said method comprising:

driving an active region of said semiconductor laser with a laser driving current I_D sufficient to generate stimulated emission of photons in said active region;

generating a modulated laser output signal P_λ

by driving said active region of said semiconductor laser with relatively high magnitude and relatively low magnitude laser driving currents I_D;

heating said active region of semiconductor laser with a heating element driving current I_H to generate heat in a heating element structure thermally coupled to said active region; and

controlling a junction temperature T_J of said active region by driving said heating element with relatively high magnitude and relatively low magnitude heating element driving currents I_H, wherein said control of said laser driving current I_D and said control of said heating element driving current I_H are such that

said heating element driving current I_H is at said relatively high magnitude when said laser driving current I_D is at a relatively low magnitude for at least a portion of a duration over which said heating element is driven by said heating element driving current I_H, and

said heating element driving current I_H decreases from said relatively high magnitude to said relatively low magnitude at a time prior to an increase in said laser driving current I_D from said relatively low magnitude to said relatively high magnitude.

2. A method as claimed in claim 1 wherein said heating element driving current I_H is controlled relative to said laser driving current I_D to compensate at least partially for thermally-induced patterning effects arising from historical thermal conditions in the semiconductor laser.

3. A method as claimed in claim 1 wherein:

said heating element driving current I_H is controlled such that said relatively low magnitude comprises a minimum current value portion a and a maximum current value portion b; and

said heating element driving current I_H transitions in time from said minimum current value portion a to said maximum current value portion b along a temperature profile that increases gradually or in stepped increments.

4. A method as claimed in claim 3 wherein said heating element driving current I_H transitions in time from:

said relatively high heating element driving current I_H to said minimum current value portion a of said relatively low heating element driving current I_H;

said minimum current value portion a to said maximum current value portion b of said relatively low heating element driving current I_H; and

said maximum current value portion b of said relatively low heating element driving current I_H to said relatively high heating element driving current I_H.

5. A method as claimed in claim 1 wherein said heating element driving current I_H is controlled so as to maintain said junction temperature T_J at a substantially constant value.

6. A method as claimed in claim 1 wherein said heating element driving current is controlled to compensate for said thermally-induced patterning effects by initiating a reduction in said heating element driving current I_H prior to an increase in said laser driving current I_D.

7. A method as claimed in claim 1 wherein said compensation for said thermally-induced patterning effects is limited to conditions where said laser driving current transitions from an off state to an on state or between two on states of different power levels.

8. A method as claimed in claim 1 wherein said control of said laser driving current I_D and said control of said heating element driving current I_H are such that:

said heating element driving current I_H is at said relatively low magnitude when said laser driving current I_D is at a relatively high magnitude for at least a portion of a duration over which said heating element is driven by said heating element driving current I_H; and

said heating element driving current I_H increases from said relatively low magnitude to said relatively high magnitude at a time prior to a decrease in said laser driving current I_D from said relatively high magnitude to said relatively low magnitude.

9. A method as claimed in claim 1 wherein the phase of said modulated laser driving current I_D is delayed relative to the phase of said heating element driving current I_H by a time delay Δ

t.

10. A method as claimed in claim 1 wherein:

said semiconductor comprises a DFB laser diode comprising a distributed feedback grating; and

said active region of semiconductor laser is heated with a micro-heating element structure extending over a substantial portion of said distributed feedback grating.

11. A method as claimed in claim 1 wherein:

said semiconductor comprises a DBR laser diode comprising a wavelength selective region, a phase matching region, and a gain region; and

said semiconductor laser is heated with a micro-heating element structure extending over said gain region.

12. A method as claimed in claim 1 wherein:

said semiconductor comprises a DBR laser diode comprising a wavelength selective region, a phase matching region, and a gain region; and

said semiconductor laser is heated with a micro-heating element structure extending over said phase matching region.

13. A method of compensating for thermally induced patterning effects in a DBR laser diode comprising a wavelength selective region, a phase matching region, and a gain region, said method comprising:

driving an active region of said semiconductor laser with a laser driving current I_D sufficient to generate stimulated emission of photons in said active region;

generating a modulated laser output signal P_λ

by driving said active region of said semiconductor laser with relatively high magnitude and relatively low magnitude laser driving currents I_D;

heating said phase matching region of said DBR laser by applying a heating element driving current I_H to a micro-heating element structure extending over at least a portion of said phase matching region to generate heat in said micro-heating element structure; and

controlling said laser driving current I_D and said heating element driving current I_H such that, for at least a portion of a duration over which said heating element is driven by said heating element driving current I_H, said heating element driving current I_H is at a relatively high magnitude when said laser driving current I_D is at said relatively low magnitude and said heating element driving current I_H is at a relatively low magnitude when said laser driving current I_D is at said relatively high magnitude to compensate at least partially for an increase in optical path length attributable to heat generated in said active region by said laser driving current I_D.

14. A method as claimed in claim 13 wherein said phase matching region is further heated by injecting electrical current I_J into said phase matching region.

15. A method as claimed in claim 14 wherein said heating element driving current I_H and said injection current I_J are controlled such that said optical path length compensation is initially achieved under the primary influence of the injection current I_J and is subsequently achieved under the primary influence of the heating element driving current I_H.

16. A method as claimed in claim 13 wherein said heating element driving current I_H in said phase matching region and said laser driving current I_D in said active region are controlled such that the total optical path length of said DBR laser is maintained at a substantially constant value.

17. A method as claimed in claim 13 wherein said heating element driving current I_H decreases from said relatively high magnitude to said relatively low magnitude at a time prior to an increase in said laser driving current I_D from said relatively low magnitude to said relatively high magnitude.

18. A method as claimed in claim 13 wherein said heating element driving current I_H transitions in time from a substantially constant relatively low magnitude to a substantially constant relatively high magnitude.

19. A method as claimed in claim 13 wherein:

said heating element driving current I_H is controlled such that said relatively low magnitude comprises a minimum current value portion a and a maximum current value portion b; and

said heating element driving current I_H transitions in time from said minimum current value portion a to said maximum current value portion b along a temperature profile that increases gradually or in stepped increments.

20. A method of compensating for thermally induced patterning effects in a semiconductor laser comprising a semiconductor substrate, an active region, a ridge waveguide, a driving electrode structure, and a micro-heating element structure, wherein:

said active region is defined within said semiconductor substrate and is configured for stimulated emission of photons under an electrical bias generated by said driving electrode structure;

said ridge waveguide is positioned to optically guide said stimulated emission of photons along a longitudinal dimension of said semiconductor laser;

said micro-heating element structure comprises a pair of heating element strips extending along said longitudinal dimension of said semiconductor laser;

said heating element strips are on opposite sides of said ridge waveguide such that one of said heating element strips extends along one side of said ridge waveguide while a remaining heating element strip extends along another side of said ridge waveguide; and

said method comprises driving an active region of said semiconductor laser with a laser driving current I_D sufficient to generate stimulated emission of photons in said active region, generating a modulated laser output signal P_λ

by driving said active region of said semiconductor laser with relatively high magnitude and relatively low magnitude laser driving currents I_D, heating said active region of semiconductor laser with a heating element driving current I_H to generate heat in a heating element structure thermally coupled to said active region, and controlling a junction temperature T_J of said active region by driving said heating element with relatively high magnitude and relatively low magnitude heating element driving currents I_H, wherein, for at least a portion of a duration over which said heating element is driven by said heating element driving current I_H, said heating element driving current I_H is at said relatively high magnitude when said laser driving current I_D is at said relatively low magnitude and said heating element driving current I_H is at said relatively low magnitude when said laser driving current I_D is at said relatively high magnitude.