Abstract: Disclosed herein is a semiconductor laser element capable of suppressing a wavelength dependency of a reflection ratio. A reflective film of the semiconductor laser element includes an L1 layer arranged at a first position from the end faces of the resonator and having a refractive index of n1; and a periodic structure configured by layering a plurality of pairs of an L2N layer and an L2N+1 layer. The L2N layer has a refractive index of n2, and the L2N+1 layer has a refractive index of n3, where n2<n3. The L1 layer has a linear expansion coefficient of ±30% with respect to a linear expansion coefficient of the substrate and is made of a film having an optical film thickness thinner than ?/4. An L2 layer arranged at a second position from the end faces of the resonator is made of a film having an optical film thickness thinner than ?/4.

Abstract: Disclosed herein is a semiconductor laser element capable of suppressing a wavelength dependency of a reflection ratio. A reflective film of the semiconductor laser element includes an L1 layer arranged at a first position from the end faces of the resonator and having a refractive index of n1; and a periodic structure configured by layering a plurality of pairs of an L2N layer and an L2N+1 layer. The L2N layer has a refractive index of n2, and the L2N+1 layer has a refractive index of n3, where n2<n3. The L1 layer has a linear expansion coefficient of ±30% with respect to a linear expansion coefficient of the substrate and is made of a film having an optical film thickness thinner than ?/4. An L2 layer arranged at a second position from the end faces of the resonator is made of a film having an optical film thickness thinner than ?/4.