A semiconductor laser includes a semiconductor laser structure having an active layer (13, 155, 217, 353). The laser structure is designed such that light in both of two polarization modes can be excited therein. First and second reflectors (14, 106; 114, 206; 216; 316) are provided, and at least one of them is a distributed reflector (14, 114, 216, 316) which determines first and second reflection wavelengths for the two polarization modes. A coupling unit (17, 18, 19; 117, 151, 152; 214, 217; 314, 351, 352, 353) is provided for coupling the laser structure and the first and second reflectors for either of the light of the two polarization modes at first and second coupling wavelengths, which respectively coincide with the first and second reflection wavelengths. One of the light of the two polarization modes at the first and second reflection wavelengths is selectively propagated along a cavity comprised of the laser structure and the first and second reflectors by a control unit (104, 110; 204, 210; 304, 305; 404, 405). Thus, light oscillates in one of the two polarization modes at the first and second reflection wavelengths.
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