Controllable optical bistability in a four-subband semiconductor quantum well system

We study optical bistability (OB) behavior based on intersubband transitions in asymmetric double quantum wells (QWs) where tunneling-induced quantum inference can be observed. The system interacts with a probe-laser field and a control laser field by means of a unidirectional ring cavity. We show that OB can be controlled efficiently by tuning the coupling strength of the tunneling, the Fano-type interference, and the intensity of the control field. The influence of the frequency detuning of the probe and control fields on the electronic OB behavior is also discussed. This investigation can be used for the optimal design of semiconductor QW systems to achieve fast and low-threshold all-optical switches, which is much more practical than that in an atomic system because of its flexible design and the controllable interference strength.