High-Contrast Multiple Quantum-Well Optical Bistable Device with Integrated Bragg Reflectors

Monolithic bistable microcavities with a GaAs/Al0.3Ga0.7As multiple quantum well active layer and AlAs/Al0.1Ga0.9As Bragg reflectors have been fabricated by metalorganic vapor phase epitaxy. The design of the whole structure is such that a good cavity finesse and a high contrast in the reflective mode are simultaneously obtained. This results in a bistability power threshold of less than 3 mW at 838 nm and a contrast ratio as high as 30:1. A new method is proposed, which allows to measure the nonlinear refractive index in a quasi-continuous regime, and in the operating conditions for bistability. The nonlinear index is shown to saturate at higher power, which evidences the need of a good cavity finesse for such bistable devices. Memory effect is then demonstrated: the sample can stay in either of its two stable states for more than 1 ms without spontaneously switching, and for input pulses as short as 60 ns. Finally we describe two-beam experiments with a new experimental configuration, also in reflection, which allows to mix the two input beams and extract the output beam with an ideal 100% efficiency.