Loss-induced enhancement of Kerr nonlinearity and optical-frequency-comb generation in a non-Hermitian cavity-QED system.

A scheme for realizing loss-induced enhancement of optical nonlinearity in a non-Hermitian cavity quantum electrodynamics system is proposed and investigated. It is shown that the system can experience an exceptional point (EP)-based phase transition process by varying the additional loss induced on the system, which leads to nontrivial phenomena with interesting counterintuitive features. We demonstrate that the Kerr nonlinearity in the system can be counterintuitively monotonically enhanced by increasing the additional loss, meanwhile, a high on-resonance linear transmission rate of the system can be maintained. Furthermore, we also demonstrate that the loss-induced nonlinearity enhancement is beneficial for realizing broadband and robust optical frequency comb. These results indicate that the additional loss can be utilized as an alternative degree of freedom to control the nonlinear dynamics of the system based on the EP-related features, which may be used in a variety of nonlinearity-based applications ranging from information processing to precision measurement.