| 摘要 |
A wavelength-tunable semiconductor laser is constructed by a semiconductor substrate; an optical waveguide provided over the upper surface of the semiconductor substrate; a front light reflection area that is provided at the front side in a laser beam emission direction by a part of the optical waveguide and comprises an SG-DBR mirror achieved by structurally repeating a portion comprising a pair of diffraction grating portion and a non-diffraction grating portion over plural periods on the assumption that the portion is set as one period; a rear light reflection area that is provided at the rear side in the laser beam emission direction by a part of the optical waveguide and comprises an SSG-DBR mirror achieved by structurally repeating, over plural periods, a portion in which the pitch of a diffraction grating pitch regularly varies from one end to the other end, both the ends being spaced at a predetermined distance, on the assumption that the portion is set as one period; an active region comprising an active layer provided between the front light reflection area and the rear light reflection area by a part of the optical waveguide; and a phase control area that is provided between the front light reflection area and the rear light reflection area by a part of the optical waveguide, and comprises a phase control layer whose refractive index is varied by current injection.
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