Bistable lasing of the vertical cavity surface emitting laser with a saturable absorber

The energy characteristics of a quantum-dot (QD) semiconductor laser with a saturable absorber in the regime of bistable lasing, which allow one to implement the device in a monolithic form, are calculated. The active and passive layers of the laser may include the same QDs. The phonon- and collision-related mechanisms of relaxation of carriers, which are substantial for the experiment, are considered. Formulas are derived for the saturation intensity, weak-signal gain/absorption coefficients, and their asymptotic dependence on the pump current. The restriction factor for filling by carriers, Fermions, and the possibility of fast capture of carriers by QDs are taken into account, and distinctions from the two-level model of saturation are demonstrated. It is shown that, to ensure the bistable mode for the laser with a saturable absorber, it is preferable to choose the resonance mode tuned to the excited state of the exciton, with predominant collision-related relaxation mechanism.