Semiconductor laser element and semiconductor laser device

A semiconductor laser element, comprising:

• a substrate;
• semiconductor layers being multi-layered, formed on the substrate and configured to include at least an active layer;
• and
• a reflective film constituted with the substrate and the semiconductor layers and provided on at least one of end faces of a resonator,
• the reflective film including:
• an L1 layer arranged at a first position counting from the one of the end faces of the resonator and having a refractive index of n1;
• and
• a periodic structure configured by layering, on the L1 layer, a plurality of pairs of an L2N layer and an L2N+1 layer, the L2N layer being arranged at a 2N-th position (where N is a positive integer) counting from the one of the end faces of the resonator and having a refractive index of n2, the L2N+1 layer being arranged at a 2N+1-th position (where N is a positive integer) counting from the one of the end faces of the resonator and having a refractive index of n3, where n2<n3,
• the L1 layer having a linear expansion coefficient within ±30% with respect to a linear expansion coefficient of the substrate and being made of a film having an optical film thickness thinner than λ/4, and
• an L2 layer arranged at a second position counting from the one of the end faces of the resonator being made of a film having an optical film thickness thinner than λ/4.