Patent ID: 8094696

Claim:
A semiconductor laser device comprising: a compound semiconductor laser body having a resonator with mutually opposed front and rear facets and emitting laser light having a wavelength of at least 1250 nm; a dielectric film, selected from the group consisting of SiO 2 , Si 3 N 4 , Al 2 O 3 , and AIN, disposed on and in physical contact with one of the front and rear facets of the resonator, the dielectric film having a thickness obtained by dividing by 2 a positive integer multiple 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 the wavelength of the laser light emitted by the compound semiconductor laser body; and a stack of a plurality of dielectric double-layer films sequentially arranged and in contact with one another, the stack of a plurality of dielectric double-layer films being disposed on and in physical contact with the dielectric film, each double-layer dielectric film having a first layer of amorphous silicon having a second refractive index, and a second layer of a material having a third refractive index that is at least 1.55 lower than the second refractive index, 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 laser light emitted by the compound semiconductor laser body.