Space–Time–Frequency Modulation Mechanisms of Monochromatic and Nonmonochromatic Electromagnetic Waves on a Digital Programmable Transmission Metasurface

Abstract By dynamically configuring unit structures, a digital programmable metasurface (DPM) can perform space, time, and frequency modulations of electromagnetic (EM) waves directly on the aperture, and hence linking the metasurface physics to digital information worlds. However, the interactions between DPMs and EM waves have not yet been systematically and efficiently depicted. Based on the Huygens–Fresnel principle and Fourier analysis, here the authors demonstrate the foundations of space–time–frequency joint controls of monochromatic or nonmonochromatic EM waves by DPM. Due to linear superposition properties of Fourier transform in the analysis, the space– and time–frequency modulations are naturally decoupled, hence enabling simultaneous and independent space–time–frequency controls of the EM waves. A transmissive DPM is designed and fabricated to interpret the space–time–frequency joint modulations. This work will facilitate the researches on DPMs and promote the applications of DPMs in wireless communications, intelligent sensing, and radar systems.