To provide a semiconductor laser device the characteristics of which are not largely affected by deviation of the design value for manufacturing the laser and which can be stably switched in polarization at a high yield, a method for driving the device, and an optical communication system using the device.

A semiconductor laser device has light guide layers 103 and 106 respectively formed on and under an active layer 104. The laser device is constituted so that a common laser bias current can be made to flow to one light guide layer 103 and active layer 104 and a current or electrical field can be independently impressed upon the other light guide layer 106. Because of the current or electrical field independently impressed upon the layer 106, the coupling states of the two polarization modes, TE mode and TM mode, of the semiconductor laser device can be changed substantially independently.