Patent ID: 8457168

Claim:
A semiconductor laser comprising first and second semiconductor optical waveguides formed on a semiconductor substrate and isolated from each other by an isolation trench, wherein: a facet pair including a facet of said first semiconductor optical waveguide adjacent to said isolation trench and a facet of said second semiconductor optical waveguide opposing said facet of said first semiconductor optical waveguide configures a composite optical reflector/connector, said isolation trench is filled with a medium having a refractive index lower than a refractive index of said semiconductor substrate and residing in a range between 1 and 2, and a wavelength filter is provided between said first optical waveguide and an optical reflector, which is combined with said first optical waveguide and said composite optical reflector/connector to configure an optical resonator, wherein: said first semiconductor optical waveguide includes a light-emitting facet, on which an antireflection film is formed, on a side counter to another facet opposing said second semiconductor optical waveguide, and is bent, in a vicinity of said light-emitting facet, by a range between 5° and 15° with respect to said light-emitting facet; said wavelength filter is a wavelength-tunable filter, which is an optical component disposed outside said semiconductor substrate; and said wavelength-tunable filter includes at least one of quartz-based PLC filter, Si waveguide filter, liquid crystal filter, and optical fiber grating filter.