Patent ID: 6850550

Claim:
A distributed feedback semiconductor laser, comprising: a lower quantum well structure extending along a resonator direction, said lower quantum well structure having a lamination of alternately stacked lower barrier layer and lower well layer having a band gap narrower than the lower barrier layer; an intermediate layer disposed on said lower quantum well structure, said intermediate layer having a band gap broader than the lower well layer and a thickness thicker than the lower barrier layer; an upper quantum well structure periodically disposed on said intermediate layer along the resonator direction, said upper quantum well structure having a lamination of alternately stacked upper well layer and upper barrier layer having a band gap broader than the upper well layer, and a diffraction-grating-burying layer disposed on said intermediate layer along the resonator direction and covering said upper quantum well structure, said diffraction-grating-burying layer having a band gap broader than the lower and upper well layers, wherein envelope of the upper quantum well structure is formed by etched profile which extends to and exposes said intermediate layer.