| 摘要 |
PROBLEM TO BE SOLVED: To obtain a wavelength tunable semiconductor laser that is superior in wavelength stability. SOLUTION: This wavelength tunable semiconductor laser comprises a semiconductor substrate 6; an optical waveguide 5 provided on the upper surface of the substrate 6; and a front reflecting region 2, which is provided on the front side of the waveguide 5 in the laser beam emission direction of laser light as part of the waveguide 5, and composed of SG-DBR mirrors repectedly arranged in a plurality of cycles 10 with each cycle 10 composed of a pair of diffraction grating sections 11a and 11a and a non-diffraction grating section 11b. The laser also comprises a rear reflecting region 3 which is provided on the rear side of the waveguide 5 in the laser beam emission direction as part of the waveguide 5 and composed of SSG-DBR mirrors repetitively arranged in a plurality of cycles 12, with each cycle 12 being composed of portions in which the pitch of diffraction gratings is changed regularly from one end to the other end of a section having a prescribed distance; an active region 1, which is provided between the reflecting regions 2 and 3 as part of the waveguide 5 and composed of an active layer; and a phase control region 4, which is provided between the reflecting regions 2 and 3 as part of the waveguide 5 and composed of a phase control layer which causes refractive index changes, when current is injected into the layer.
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