Distributed feedback semiconductor laser and method for fabricating the same

摘要

A distributed feedback semiconductor laser which includes a semiconductor substrate of a first conductive type; a semiconductor multi-layer structure provided on the semiconductor substrate and including an active layer for generating laser light; and a gain-coupled diffraction grating provided between the semiconductor substrate and the semiconductor multi-layer structure. The diffraction grating includes a plurality of curved projections periodically arranged at a surface of the semiconductor substrate and a quantum well light absorption layer for covering the plurality of curved projections. The quantum well light absorption layer includes a light absorption area having a first thickness at each border between two adjacent curved projections and a non-light absorption area having a second thickness which is smaller than the first thickness at a top of each of the curved projections. The light absorption area has a band gap which is narrower than a band gap of the active layer, and the non-light absorption area has a band gap which is wider than the band gap of the active layer.