Dfb laser diode having a modified profile of linewidth enhancement factor

摘要

A distributed feedback laser diode comprises an active layer (13), a waveguide layer (12), a corrugation grating (11a) for causing a Bragg reflection of an optical beam, and a phase shift point (11A) provided in the corrugation grating. The active layer is formed of a first region (13A), a second region (13B) and a third region (13C) aligned in a longitudinal direction such that the first region and third region are located at both sides of the second region in the first direction, wherein the first region, the second region and the third region have first, second and third profiles of the linewidth enhancement factor respectively such that the linewidth enhancement factor of the second profile is smaller than the linewidth enhancement factor of the first and third profiles and the linewidth enhancement factor changes stepwise at a boundary between the first region and the second region and at a boundary between the second region and the third region.