Patent ID: 7362786

Claim:
A semiconductor laser element comprising: a substrate made of GaAs of a first conductive type; a lower cladding layer formed above said substrate and made of AlGaInP of said first conductive type; a lower optical waveguide layer formed above said lower cladding layer and made of AlGaInP; a quantum-well active layer formed above said lower optical waveguide layer and made of InGaP; an upper optical waveguide layer formed above said quantum-well active layer and made of AlGaInP; and an upper cladding layer formed above said upper optical waveguide layer and made of AlGaInP of a second conductive type; wherein said substrate has an intrinsic lattice constant a, and said quantum-well active layer has a thickness dw, an intrinsic lattice constant a+Δa, and a degree of mismatch Δa/a with said substrate, and the thickness dw and the degree of mismatch satisfy conditions, −0.6%≦Δ a/a ≦−0.3%, and 10 nm≦dw≦20 nm; and said semiconductor laser element has a resonator length Lc, a light-emission end facet exhibiting a first reflectance Rf, and an end facet being located opposite to the light-emission end facet and exhibiting a second reflectance Rr, and the resonator length Lc and the first and second reflectances Rf and Rr satisfy conditions, Lc≧400 μm, and Rf×Rr ≧0.5.