New model of nonlinear metasurfaces：space-time-coding digital metasurfaces

A metasurface is an ultrathin artificial surface, composed of sub-wavelength structures, which exhibits an extraordinary capability in controlling electromagnetic waves. It has attracted more and more interest owing to its huge potential in enhancing nonlinear effects. In recent years, space-time-coding digital metasurfaces with field programmable capabilities and spatiotemporally modulated electromagnetic parameters have been successfully used to manipulate nonlinear electromagnetic effects accurately and efficiently, and have thus become a new model of nonlinear metasurfaces. In this article, we first briefly outline the basic concepts of space-timecoding digital metasurfaces, and then review the recent research on nonlinear electromagnetic manipulation, including harmonic generation, electromagnetic parameter control, and nonlinear wavefront control. Finally, current challenges and future development prospects will be summarizeds.