Wavefront shaping and modulation with resonant electro-optic phase gradient metasurfaces

Abstract

Phase gradient metasurfaces have revolutionized modern optical components by significantly reducing the path length of bulk optics while maintaining high performance. However, their geometric design makes dynamic modulation challenging, with devices facing a trade-off between the modulation range and efficiency. Here, we introduce Silicon-on-Lithium Niobate (LNO) high-Quality-factor (high-Q) metasurfaces for efficient electro-optic wavefront shaping and modulation. Periodic perturbations within Si metasurface elements allow incident light to be weakly coupled into guided modes, generating high-Q resonances that manifest in the far-field diffraction spectrum. The near field of each Si element spatially overlaps with the LNO substrate, enabling electrically tunable modulation of the resonant frequency. Using full-field simulations, we demonstrate near-infrared, dynamically tunable beamsteering, and beamsplitting metasurfaces. First, we demonstrate beamsteering metasurfaces whose +1st order diffracted intensity can be modulated from 70% to 7% absolute efficiency near the resonant frequency with applied electric fields of order V/μm. Next, we design a tunable beam splitter, switching between direct, 0th order transmission and beamsplitting with the application of 30 V across the metasurface. Our high-Q electro-optic metasurfaces provide a foundation for efficient, time-dependent transfer functions in subwavelength footprints.