Dynamic properties of optically switched bistable semiconductor lasers

The dynamic properties of optically switched semiconductor lasers biased from below-to-above threshold are presented theoretically. An analytic expression for the carrier density in the active region of a laser with respect to time is given to discuss the switching-off time. The numerical results show that the switching-on time and the switching-off time are governed by different mechanisms. They are related to the laser parameters for the free-running laser. They also depend on the optical power and the time duration of the input optical pulse and the frequency detuning between the frequency of the free-running laser and that of the input optical pulse. A small frequency detuning is desired to reduce both the switching-on and switching-off times. However, there is an optimal detuning to maximize the energy of the output optical pulse. On the other hand, for fixed detuning and injection power, a larger bias current results in a shorter switching-off time, but a lower bias current results in a shorter switching-on time.