Patent ID: 7061963

Claim:
A semiconductor laser device comprising: an n type InP substrate; an n type diffraction grating layer supported by said InP substrate, lattice matching with InP, and having a refractive index different from the refractive index of InP, said n type diffraction grating layer having concave portions periodically disposed alongside of one another in a laser optical waveguide direction; an n type InP layer containing a Group VI element as a dopant impurity in a concentration of at least 1×10 19 cm −3 and filling the concave portions of said diffractive grating layer so that said InP layer and said diffraction grating layer have substantially co-planar surfaces; an n type first cladding layer disposed on the substantially co-planar surfaces of said InP layer and said diffraction grating layer; an active layer disposed on said first cladding layer; and a p type second cladding layer disposed on said active layer.