Dependences of the polarization-bistable condition on the coefficients of linear and nonlinear gains of a laser diode are analyzed, including S-shaped and pitchfork types of bistability, in the optical output versus injection current characteristics. Moreover, the steady-state and dynamic characteristics of the optical output for optical input are investigated, taking account of a detuning of incident optical beam from the cavity resonant frequency of a polarization-bistable laser diode, TE-TM polarization switching is shown to be attained in the optical output of the polarization-bistable laser diode in a very fast switching time less than a nanosecond by the application of TE and TM optical input pulses.