Phase Space of Tristability in Dual Injection-Locked Fabry-Perot Laser Diodes

We investigate theoretically the case of dual injection-locking, in which the two light signals are simultaneously externally injected into the cavity of a slave Fabry-Perot laser diode. We show that dual injection-locking leads to formation of new stationary points, and potentially to optical tristability of the slave laser. We show that a region in which the slave laser exhibits three stable steady-states occurs only for sufficiently different frequency detunings of the two injection signals. Moreover, the slave laser tunability depends on the choice of injection modes, and strongly depends on the slave laser bias current, with an optimal value around 2 times threshold current