Patent ID: 7197055

Claim:
A semiconductor laser comprising: an optical resonator formed by processing either end of an optical waveguide to be a partially reflective surface, the optical waveguide being formed from a 1 st conductive-type cladding layer, an active layer and a 2 nd conductive-type cladding layer layered in the stated order; and a current blocking layer formed on 1 st and 2 nd regions of the optical resonator, the 1 st region extending a 1 st length from a light-emission end surface of the optical resonator and the 2 nd region extending a 2 nd length from an opposite end surface of the optical resonator, wherein a section of the active layer extending a predetermined length from the light-emission end surface and a section of the active layer extending a predetermined length from the opposite end surface are formed to have an energy bandgap larger than a remaining section thereof, and a horizontal divergence angle of light emerging from the light-emission end surface is managed by setting the 1 st length to be longer than a distance over which current flowing into the 1 st region from a 3 rd region of the optical resonator that excludes the 1 st and 2 nd regions is reduced to 1/e by diffusion, where e is a base of a natural logarithm.