Patent ID: 8233514

Claim:
A semiconductor laser device comprising: a compound semiconductor laser body having a resonator with facets mutually opposed; a dielectric film, selected from the group consisting of SiO 2 , Si 3 N 4 , and AlN, disposed on one of the facets of the resonator, and in contact with the facet of the resonator, the dielectric film having a thickness 1/25 or less of a first in-medium wavelength determined by a first refractive index, which is the refractive index of the material composing the dielectric film, and wavelength of emitted light of the compound semiconductor laser body; and a first dielectric double layered film on the dielectric film, having a first layer of amorphous silicon and a second layer of a material having a third refractive index, lower than a second refractive index, which is the refractive index of amorphous silicon, the first layer being closer to the dielectric film than the second layer, and having a thickness ¼ of a second in-medium wavelength determined by the second refractive index and the wavelength of the emitted light, and the second layer having a thickness ¼ of a third in-medium wavelength determined by the third refractive index and the wavelength of the emitted light.