Large optical nonlinearity enhancement under electronic strong coupling

Nonlinear optical responses provide a powerful way to understand the microscopic interactions between laser fields and matter. They are critical for plenty of applications, such as in lasers, integrated photonic circuits, biosensing medical tools. However, most materials exhibit weak nonlinearities or long response times when they interact with intense fields. Here, we strongly couple exciton organic molecules an mode Fabry-Perot cavity, achieve enhancement nonlinear complex refractive index by two orders magnitude compared that uncoupled condition. Moreover, coupled system shows ultrafast ~120 fs extract from cross-correlation measurements. The large nonlinar coefficients this work paves exploring strong coupling effects on various third-order phenomena technological applications.