Nonlinear Metasurface Based on Giant Optical Kerr Response of Gold Quantum Wells

A nonlinear metasurface is demonstrated numerically based on the recently developed quantum-sized gold film. The active functionality of the metasurface is realized by varying the incident optical power through the ultrahigh Kerr nonlinearity of the quantum-sized gold films. In the low power region, the device acts as a normal reflecting surface, while it becomes a phase grating with most energy in the 1 diffraction modes when the optical power increases and the nonlinear effect plays a dominating role. Unlike previously demonstrated nonlinear metasurfaces focusing on nonlinear frequency generation, the functionality of our device may be modulated by the power of incident light. As the first nonlinear metasurface that is based on optical Kerr nonlinearity, our design may lead to various applications, such as optical limiters and tunable phase gratings.