Programmable Controlling of Multiple Spatial Harmonics via a Nonlinearly-Phased Grating Metasurface

By modulating physical characteristics (amplitude, phase, polarization, etc.) at the subwavelength scale, metasurfaces have shown prominence in controlling electromagnetic waves. However, metasurfaces with linear phase distributions face difficulties in various wavefront reconstructions intentionally and efficiently, and complex-amplitude metasurfaces with independent amplitude and phase modulations are preferable. Here, a new scheme of the reprogrammable nonlinearly-phased grating metasurface, comparable to complex-amplitude metasurfaces, enabling real-time and versatile control of multiple spatial harmonics by modulating the phase is reported. Through elaborate and instantaneous programming of nonlinear phase distributions at the metasurface interface, desired electromagnetic wavefronts can be reconstructed in real-time by reconfiguring the generation and suppression of multiple spatial harmonics and by customizing reflection angles and reflection intensities of each spatial harmonic. To corroborate this design, generation and suppression, intensity tailoring, and retro-reflection of multiple spatial harmonics are presented and verified experimentally. This work provides a real-time and efficient way to implement dynamical reconstruction of various electromagnetic wavefronts and can be further applied to other potential scenarios such as holography, imaging, and wireless communication.