Patent ID: 7590158

Claim:
A semiconductor laser comprising: a semiconductor substrate of a first conductivity type; a buffer layer of the first conductivity type, containing AlGaAs having an Al ratio of at least 0.2 and less than 0.3, and having a thickness in a range from 0.2 μm to 0.6 μm, on said semiconductor substrate; a first cladding layer of the first conductivity type, on said buffer layer; an active layer containing a quantum well, on said first cladding layer; a second cladding layer of a second conductivity type, on said active layer; and a window region disordered by an impurity and located proximate an end surface of a laser resonator, wherein said window region comprises parts of said buffer layer, said first cladding layer, said active layer, and said second cladding layer and extending in an optical waveguide direction, and said window region extends through only part of the thickness of said buffer layer and does not extend to said semiconductor substrate.