Space-time metasurfaces employ a spatial and temporal phase-gradient to impart momentum to input light in space and frequency. In this work, we used a reflective gate-tunable ITO-based metasurface operating at 1530 nm to generate diffraction of frequency-shifted light up to 1 MHz. Our device consists of an array of interdigitated plasmonic nanoantennas with two electrical contacts that are modulated with identical electrical waveforms, time-delayed by half a period, to diffract frequency-shifted light. The simultaneous control of spatial and spectral properties of light enabled by space-time metasurfaces is highly desired in applications such as LiDAR, LiFi, and space communication.
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