Patent ID: 7359423

Claim:
A distributed feedback laser diode comprising: a semiconductor substrate; an active layer supported by said semiconductor substrate; a cladding layer supported by said active layer; a diffraction grating near said active layer and extending along a waveguide direction, said diffraction grating having at least one phase shift portion; and two facets transverse to said active layer, wherein both facets of said distributed feedback laser diode have thereon an antireflective film having a reflectance of no more than 3%, said diffraction grating does not extend into end regions of said distributed feedback laser diode, each end region extending 1 μm-20 μm from a respective one of said facets toward an opposite end in the waveguide direction, said active layer extends into at least one of said end regions to one of said facets, and the portions of said cladding layer within said end regions, into which said diffraction grating does not extend, each have a first part with a carrier concentration lower than carrier concentration of a second part of said cladding layer, said second part being in a region in which said diffraction grating is located.