Laser device, light modulation device, and optical semiconductor device

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.