Distributed feedback laser diode

A semiconductor laser includes an active layer on an n-type InP substrate. A diffraction grating and a p-type InP cladding layer are above the active layer. The diffraction grating has at least one phase shift portion. Facets of the distributed feedback laser each have thereon an antireflective film having a reflectance of 3% or less. The diffraction grating does not extend into end regions of the distributed feedback laser, each end region extending 1 mum-20 mum from a respective one of the facets toward an opposite end in a waveguide direction.