| 摘要 |
PROBLEM TO BE SOLVED: To realize more efficient and more stable polarization switching by applying control for switching the polarization to the area in which the refractive index may be changed easily by external control, among a plurality of regions having active layer and diffraction grating in the resonance direction. SOLUTION: In a region I of a semiconductor laser, an equivalent refractive index is large and in a region II, an equivalent refractive index is small. By injecting uniform current, distribution of beam is intensified in the area where aλ/4 phase shift section is provided, a carrier density becomes small in the region I, while a carrier density becomes large in the region II. Under this condition, it is assumed here that an output beam has the TE polarization. When the carrier is increased by increasing a current to be injected to the region I, the refractive index will be changed by a relatively large extent depending on such an increase. When the phase of the TM polarization in the region II is matched with the phase of the polarization in the region 1 because the Bragg wavelength in the part of the region I is changed to the short wavelength side, the TM polarization beam can be output.
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