Patent ID: 7274720

Claim:
A substrate made of GaAs; a lower optical waveguide formed above a lower cladding layer that being formed above said substrate having a stripe shape with a width smaller than a width which the substrate and made of a material of a first conductive type, where at least one compressive-strain quantum-well active layer being formed above said lower optical waveguide layer and made of InGaAs, and having a stripe shape with a width smaller than said substrate width; an upper cladding layer formed above an upper optical waveguide layer being formed above compressive-strain quantum-well active layer and made of a second conductive type, and having a stripe shape with a width smaller than said substrate width; a current-blocking layer formed on both sides of compressive-strain quantum-well active layer so that the at least one compressive-strain quantum-well active layer is sandwiched between two portions of the current-blocking layer; and trenches being formed through said current-blocking layer and extending along a direction of a laser resonator formed in said semiconductor laser element.