Bistable operation of a semiconductor laser

Bistability has been achieved in the output of GaAs-AlAs injection heterojunction lasers made from LOC structures in which the bandgap of the material of one of the emitters, serving as a saturable absorber, is just slightly greater than the bandgap of the material making up the active layer. The composition varies smoothly over the thickness. The lasers had a wide contact of 150 microns, while the length of the Fabry-Perot resonator was 450-500 microns. The lasers were pumped with bell-shaped current pulses in order to smoothly vary the instantaneous value of the current through the laser diode during a single pulse. Under lasing conditions, when a certain instantanous pump current was reached, the peak intensity of the laser output rose sharply and the shape of the output pulse changed markedly. The dependence of the amplitude of the output pulse on that of the pump current pulse is shown.