Coherent illumination of time-varying metasurfaces: An approach to control frequency response.

Coherent metasurfaces are illuminated by several waves that work in synchronism to control electromagnetic wave interference. However, these metasurfaces are temporally stationary, and the illumination occurs only at one specific frequency. In this paper, we present a new class of coherent metasurfaces which control illuminations at multiple frequencies, and, more importantly, their properties are temporally modulated. In this scenario, the time-varying properties of those metasurfaces are synchronized with the coherent illumination, which allows creating novel interference phenomena and full control over the frequency response of the metasurface. In particular, we present a comprehensive study of possibilities offered by dynamic resistive layers and show how to use them to design multifrequency perfect absorbers. We also demonstrate possibilities of remote tuning of the absorption level. We hope that this work opens up novel avenues in wave engineering using coherent illumination and modulation of metasurface parameters.