Patent ID: 7729401

Claim:
A semiconductor laser device comprising: a cavity structure including a first clad layer, an active layer and a second clad layer sequentially formed on a substrate, wherein the second clad layer has a stripe portion extending between a front end face from which laser light is extracted and a rear end face opposite to the front end face, the stripe portion has a first region located closer to the front end face, a second region located closer to the rear end face and a change region whose stripe width changes located between the first region and the second region, the effective refractive index difference between the inside and outside of the stripe portion in the change region is greater than the effective refractive index difference between the inside and outside of the stripe portion in the first region, the active layer is made of a material represented by a general formula (Al a Ga b ) c In 1-c P (0≦a<1, 0<b≦1, a+b=1, 0<c<1), the first and second clad layers are made of a material represented by a general formula (Al d Ga e ) f In 1-f P (0<d<1, 0<e<1, d+e=1, 0<f<1), and the stripe portion is a ridge stripe portion, and wherein the device further comprises a first current block layer covering sidewalls of the ridge stripe portion in the first region and a second current block layer covering sidewalls of the ridge stripe portion in the change region, and the refractive index of the first current block layer is greater than the refractive index of the second current block layer.