Self-heating mitigation in an acoustically tunable distributed feedback laser

1. A laser assembly, comprising:

a semiconductor laser with an active semiconductor region for emitting an optical signal in response to a drive current that is applied to the active semiconductor region;

a drive circuit for generating the drive current in accordance with an input signal and applying the drive current to the active semiconductor region;

a controllable oscillator for generating a periodic electric signal that is applied to the semiconductor laser to generate a surface acoustic wave in or near the active semiconductor region such that a diffraction grating structure is created in or near the active semiconductor region by the surface acoustic wave, an emission wavelength of the active semiconductor region being determined by a periodicity of the diffraction grating structure, wherein the controllable oscillator is configured to set a frequency of the periodic electric signal in accordance with a control signal; and

a control circuit for generating the control signal for the controllable oscillator in such a manner that a shift of the emission wavelength away from a predetermined emission wavelength that results from heating of the active semiconductor region during emission of the optical signal is at least partially compensated by an opposite shift of the emission wavelength that results from a change of the periodicity of the diffraction grating structure in or near the active semiconductor region.

2. The laser assembly according to claim 1 , wherein the control signal is a time-dependent control signal.

3. The laser assembly according to claim 1 , wherein the control circuit is configured to generate the control signal in such a

manner that the controllable oscillator ( 140 ) increases the frequency of the periodic electric signal during emission of the optical signal.

4. The laser assembly according to claims 1 , wherein the control signal comprises a constant contribution corresponding to the predetermined emission wavelength and a time-dependent contribution corresponding to the opposite shift of the emission wavelength.

5. The laser assembly according to claims 1 , wherein the control circuit is configured to generate the control signal on the basis of the input signal.

6. The laser assembly according to claims 1 , wherein the input signal comprises a rectangular pulse indicating a transmission period, and the control signal is generated on the basis of the rectangular pulse.

7. The laser assembly according to claim 6 ,

wherein the control circuit comprises a pulse shaping circuit for generating an output voltage level depending on the rectangular pulse; and

the controllable oscillator is a voltage controlled oscillator.

8. The laser assembly according to claim 7 , wherein the pulse shaping circuit comprises a look-up table or a filter unit.

9. The laser assembly according to any claims 1 ,

wherein the input signal comprises a data signal indicative of data to be transmitted by means of the optical signal;

the control circuit is configured to determine an envelope of the data signal; and

the control signal is generated on the basis of the envelope of the data signal.

10. The laser assembly according to claim 9 ,

wherein the control circuit comprises an averaging circuit for determining the envelope of the data signal and a pulse shaping circuit for generating an output voltage level depending on the determined envelope of the data signal; and

the controllable oscillator is a voltage controlled oscillator.

11. A method of driving a semiconductor laser having an active semiconductor region for emitting an optical signal in response to a drive current that is applied to the active semiconductor region, the method comprising:

generating the drive current in accordance with an input signal and applying the drive current to the active semiconductor region;

generating a surface acoustic wave in or near the active semiconductor region by applying a periodic electric signal to the semiconductor laser such that a diffraction grating structure is created in or near the active semiconductor region by the surface acoustic wave, an emission wavelength of the active semiconductor region being determined by a periodicity of the diffraction grating structure; and

controlling a frequency of the periodic electric signal in such a manner that a shift of the emission wavelength away from a predetermined emission wavelength that results from heating of the active semiconductor region during emission of the optical signal is at least partially compensated by an opposite shift of the emission wavelength that results from a change of the periodicity of the diffraction grating structure in or near the active semiconductor region.

12. The method according to claim 11 , wherein controlling the frequency of the electric signal involves increasing the frequency of the periodic electric signal during emission of the optical signal.

13. The method according to claim 11 , wherein controlling the frequency of the electric signal involves controlling the frequency of the periodic electric signal on the basis of the input signal.

14. The method according to claims 11 ,

wherein the input signal comprises a rectangular pulse indicating a transmission period; and

controlling the frequency of the periodic electric signal involves controlling the frequency of the periodic electric signal on the basis of the rectangular pulse.

15. The method according to claims 11 ,

wherein the input signal comprises a data signal indicative of data to be transmitted by means of the optical signal; and

controlling the frequency of the periodic electric signal involves:

determining an envelope of the data signal and controlling the frequency of the periodic electric signal on the basis of the envelope of the data signal.