DFB semiconductor laser and method for production thereof

摘要

A DFB laser (10) has a semiconductor substrate (1) of a first conductivity type, a semiconductor multilayer structure (7) which is formed on the semiconductor substrate (1) and an active layer (4) for producing laser light and a gain-coupled diffraction grating which is arranged between the semiconductor substrate (1) and the semiconductor multilayer structure (7). The diffraction grating comprises a multiplicity of arched projections which are periodically arranged on one surface of the semiconductor substrate, and a quantum-well light-absorption layer for covering the multiplicity of arched projections. A quantum-well light-absorption layer has a light-absorbing region which has a first thickness on each boundary between two neighbouring arched projections and a region which does not absorb light and has a second thickness on each of the apices of each of the arched projections which is smaller than the first thickness. The light-absorbing region has a band gap which is narrower than a band gap of the active layer, and the region which does not absorb light has a band gap which is wider than the band gap of the active layer (Figure 5).