US Patent 7274720 Semiconductor laser element having InGaAs compressive-strained quantum-well active layer

In a semiconductor laser element, a lower cladding layer, a lower optical waveguide layer, an InGaAs compressive-strain quantum-well active layer, an upper optical waveguide layer, and an upper cladding layer are formed in this order in a stripe-shaped region on a substrate. A current-blocking layer is formed on both sides of the compressive-strain quantum-well active layer so that the compressive-strain quantum-well active layer is sandwiched between two portions of the current-blocking layer, and trenches extending along the direction of the laser resonator are formed through the current-blocking layer. Instead of providing the trenches, the widths of the layers formed above the substrate are reduced so as to form a ridge structure.