Patent ID: 7826507

Claim:
A semiconductor laser device including semiconductor films on a substrate, comprising: a cavity extending in a propagation direction of a laser beam having wavelength λ; a first facet on a first end of the cavity and through which the laser beam is emitted; a second facet on a second end of the cavity and reflecting the laser beam; and a highly reflective film on said second facet and consisting of an insulating multi-layered film of at least three layers, wherein said highly reflective film comprises a first layer which is in contact with said second facet, is constituted of Al 2 O 3 , and has a thickness smaller than λ/4n wherein n is the refractive index of Al 2 O 3 , a second layer which is in contact with said first layer and is constituted of any of SiO 2 , MgF 2 , NaF, Ca 2 F, CeF 3 , LaF 3 , LiF, and NdF 3 , and a third layer which is in contact with said second layer and has a refractive index different from the refractive index of said second layer.