Controlling optical multistability and bistability in four-level cascade quantum wells

Optical multistablity (OM) and bistability (OB) are investigated theoretically in the four-level cascade quantum wells (QWs) with two similar transitions for the probe laser. It is interesting that the system can be transited from OM to OB by enhancing the coupling laser field or reducing its frequency detuning. In the same time, both of them can also be used to control the OM behavior along with the other corresponding parameters such as the electronic cooperation parameter, the probe laser frequency detuning and the decay rate. Such a system is more practical than those in the atomic systems for the flexibility of QWs, and may be used in the all optical switches or other solid-state quantum information devices.