A QW diode laser whose polarization can be switched. In one embodiment, the device incorporates a tensile strained quantum well active region, whose thickness is adjusted so that the heavy hole and light hole band edges are of the same energy. Since the heavy hole transition provides TE-mode gain, while the light hole band provides mostly TM-mode gain, the resulting laser polarization will be very sensitive to the threshold carrier density. With an intracavity loss modulator in such a structure, the polarization could be switched. Other switching techniques are also described.