Wavelength-controlled semiconductor laser device

1. A semiconductor laser device comprising

a laser diode device with

a semiconductor laser diode,

an integrated photodiode and

electric contacts for electrically connecting said semiconductor laser diode and said integrated photodiode, said semiconductor laser device further comprising

feedback control circuitry for setting or stabilizing a laser wavelength by stabilizing or setting a temperature of the laser diode device, said feedback control circuitry being set up to generate a heating voltage or current in response to a measured temperature-dependent parameter,

said heating voltage or current being applied to electric contacts of said laser diode device, of which at least one also electrically connects said semiconductor laser diode or said integrated photodiode so that said heating current flows through the laser diode device and heats said semiconductor laser diode.

2. The semiconductor laser device according to claim 1 , wherein said laser diode device comprises a vertical cavity surface emitting laser with said integrated photodiode.

3. The semiconductor laser device according to claim 1 , wherein said integrated photodiode is operated at reverse bias, and said feedback control circuitry for stabilizing or setting the temperature of the laser diode device is set up to set the voltage across the integrated photodiode which is thereby heated by a photocurrent induced by a received light.

4. The semiconductor laser device according to claim 1 , wherein at least one of said electric contacts for electrically connecting the semiconductor laser diode and the integrated photodiode has two terminal points connecting to said feedback control circuitry, wherein said heating current flows between said two terminal points.

5. The semiconductor laser device according to claim 1 , wherein the heating current or voltage is fed between two laterally separated electric contacts on a common surface, at least one of the electric contacts contacting said semiconductor laser diode or said integrated photodiode.

6. The semiconductor laser device according to claim 5 , wherein said separated electric contacts are made from different materials.

7. The semiconductor laser device according to claim 1 , wherein the input of the feedback control circuitry is connected to the electric contacts of said semiconductor laser diode, which feedback control circuitry measures a forward voltage of the laser diode.

8. The semiconductor laser device according to claim 7 , wherein said semiconductor laser diode is heated by the feedback control circuitry as long as the operating voltage comes below a predefined value at a fixed operating current if the laser diode temperature is lower than a temperature corresponding to a predetermined wavelength.

9. The semiconductor laser device according to claim 1 , wherein the feedback control circuitry measures a parameter corresponding to a resistance of a part heated by said heating current or voltage.

10. The semiconductor laser device according to claim 1 , wherein the input of the feedback control circuitry is connected to the electric contacts of said integrated photodiode, and the light output as measured by the integrated photodiode is fed as an input parameter to the feedback control circuitry which sets the heating current or voltage in dependence upon the light output.

11. The semiconductor laser device according to claim 1 , wherein the semiconductor laser diode is formed as a mesa structure on a substrate, which said mesa structure is at least partly surrounded by a trench in said substrate.

12. The semiconductor laser device according to claim 1 , wherein the semiconductor laser diode is formed as a mesa structure on a substrate, wherein a partially oxidized layer is arranged between said mesa and said substrate.