Tunable nonlinear coherent perfect absorption and reflection in cavity QED
We propose and analyze a scheme for realizing tunable coherent perfect absorption (CPA) and reflection (CPR) in a three-level $\Lambda$-type atom-cavity system. With EIT-type interference induced by a coherent coupling laser, the scheme provides a new method of attaining tunable near CPR at two-photon resonance. By different coupling strength, the system can be excited from linear CPA regime into nonlinear even bistable CPA regime without changing the frequency of the probe field, where the hysteresis cycle of the bistability is controllable. In addition, the CPA regime can be transferred into the near CPR regime with controllable atomic coherence and linear absorption induced by an incoherent pump field. Our work suggests a mechanism for manipulation on extreme absorption (0% and 100%), which can potentially be applied in logical gates and optical switches for coherent optical computing and communication.