Laser device, light modulation device, and optical semiconductor device

1. A laser device comprising:

an optical semiconductor device formed of a compound semiconductor material; and

a wavelength-selective reflection device including optical waveguides,

wherein the optical semiconductor device includes

a first gain waveguide,

a second gain waveguide,

a DBR waveguide formed between the first gain waveguide and the second gain waveguide,

a first electrode configured to inject current in the first gain waveguide,

a second electrode configured to inject current in the second gain waveguide, and

an antireflection film formed on a device facet to which the second gain waveguide is connected,

wherein the optical waveguides in the wavelength-selective reflection device reflect light having a predetermined wavelength from incident light in the optical waveguides, and

wherein the first gain waveguide is optically coupled with the wavelength-selective reflection device, so that a laser resonator is formed by the DBR waveguide and the wavelength-selective reflection device, and the first gain waveguide functions as a gain medium.

2. The laser device according to claim 1 ,

wherein another antireflection film is formed on a facet to which the first gain waveguide is connected in the optical semiconductor device.

3. The laser device according to claim 1 ,

wherein there is further disposed an optical waveguide which is optically connected to the second gain waveguide of the optical semiconductor device and is formed on a same substrate on which the wavelength-selective reflection device is formed.

4. The laser device according to claim 1 ,

wherein the first gain waveguide, the second gain waveguide, and the DBR waveguide are formed of a material including InP.

5. The laser device according to claim 1 ,

wherein core layers of the first gain waveguide, the second gain waveguide, and the DBR waveguide are formed of a material including InGaAsP.

6. The laser device according to claim 1 ,

wherein a band gap wavelength in a compound semiconductor material forming a core layer of the DBR waveguide is shorter than a band gap wavelength in a compound semiconductor material forming core layers of the first gain waveguide and the second gain waveguide.

7. The laser device according to claim 1 ,

wherein the first gain waveguide, the second gain waveguide, and the DBR waveguide are formed on a lower cladding which is formed of a compound semiconductor material including a first conductivity type of InP, and

wherein an upper cladding, which is formed of a compound semiconductor material including a second conductivity type of InP, is formed on the first gain waveguide, the second gain waveguide, and the DBR waveguide.

8. The laser device according to claim 7 ,

wherein a diffraction grating is formed in the lower cladding in the area where the DBR waveguide is formed.

9. The laser device according to claim 1 ,

wherein intensity of laser light which is emitted from a facet of the second gain waveguide can be changed by fixing a current in the first gain waveguide and changing a current in the second gain waveguide.

10. The laser device according to claim 1 ,

wherein a facet to which the first gain waveguide of the optical semiconductor device is connected is opposite to the facet to which the second gain waveguide of the optical semiconductor device is connected.

11. The laser device according to claim 1 ,

wherein a facet to which the first gain waveguide is connected and a facet to which the second gain waveguide is connected are same.

12. The laser device according to claim 1 ,

wherein the wavelength-selective reflection device includes

a first optical waveguide,

a second optical waveguide,

a ring resonator formed between the first optical waveguide and the second optical waveguide and formed of an optical waveguide,

a reflection mirror formed in a part of the second optical waveguide.

13. The laser device according to claim 12 ,

wherein the reflection mirror is formed by periodically changing a width of an optical waveguide.

14. The laser device according to claim 12 ,

wherein the reflection mirror is a loop mirror.

15. The laser device according to claim 1 ,

wherein the optical waveguides are Si optical waveguides.

16. A light modulation device comprising:

the laser device according to claim 1 ; and

an optical modulator,

wherein laser light, which is emitted from a facet of the second gain waveguide, coupled to an end surface of an optical waveguide in the optical modulator, and then, the laser light is modulated in the optical modulator and is emitted from other end surface of an optical waveguide of the optical modulator.

17. The light modulation device according to claim 16 ,

wherein a ring resonator is formed at least at a part of the optical modulator.

18. The light modulation device according to claim 17 ,

wherein a circumference length of a ring resonator in the wavelength-selective reflection device is the same as the circumference length of the ring resonator formed in the optical modulator.

19. The light modulation device according to claim 16 ,

wherein the wavelength-selective reflection device and the optical modulator are formed on a same substrate.

20. An optical semiconductor device comprising:

a first gain waveguide formed of a compound semiconductor material;

a second gain waveguide formed of a compound semiconductor material;

a DBR waveguide formed between the first gain waveguide and the second gain waveguide and formed of a compound semiconductor;

a first electrode configured to inject current in the first gain waveguide; and

a second electrode configured to inject current in the second gain waveguide,

wherein an antireflection film is formed on a facet to which the first gain waveguide is connected and a facet to which the second gain waveguide is connected.