Patent ID: 8767788

Claim:
A semiconductor laser device comprising: a semiconductor substrate; a semiconductor laminated section which includes a first conductivity type cladding layer, an active layer, and a second conductivity type cladding layer, sequentially stacked on the semiconductor substrate, and which has a front facet and a rear facet transverse to a resonator length direction; a ridge section located on a top of the semiconductor laminated section; and a pair of terrace sections located on the top of the semiconductor laminated section, and sandwiching and spaced from the ridge section, wherein the ridge section has a width of at least 50 μm, the active layer is divided into an active region, a pair of under-the-terrace-section regions, and a pair of cladding regions, wherein the active region is located below the ridge section, as viewed in plan from the top of the semiconductor laminated section, the under-the-terrace-section regions are located on opposite sides of the active region and each of the under-the-terrace regions is located below a respective one of the pair of terrace sections, as viewed in plan from the top of the semiconductor laminated section, each of the cladding regions located between the active region and a respective one of the pair of under-the-terrace-section regions, and the under-the-terrace-section regions have a higher effective refractive index than the cladding regions due to location opposite respective ones of the pair of terrace sections, the semiconductor laser device satisfies (2π/λ)×(n a 2 −n c 2 ) 1/2 ×(W/2) >π/2, where λ represents lasing wavelength of the semiconductor laser device, n a represents effective refractive index of the active region, n c represents effective refractive index of the cladding regions, and W represents the width of the active region, the pair of terrace sections sandwich a central portion of a length of the ridge section, the length of the ridge section extending, in the resonator length direction, a top portion of the semiconductor laminated section includes first sections sandwiching an end portion of the ridge section on a front facet side of the semiconductor laminated section, and second sections sandwiching an end portion of the ridge section on a rear facet side of the semiconductor laminated section and the first and second sections sandwich the terrace sections, as viewed in plan from the top of the semiconductor laminated section, and the first sections and/or the second sections are closer to the semiconductor substrate than are the ridge section and the pair of terrace sections.