Jiyong Shim | Searcharxiv

arXiv2026

Localized high-Q resonances enable electrically defined beam steering in lithium niobate metasurfaces

High-speed beam steering for LiDAR and optical communication requires independent, reconfigurable control of optical phase. We demonstrate a metasurface combining lithium niobate's Pockels effect with high-Q (Q > 1700) silicon guided-mode resonance nanoantennas whose localized resonances allow individual electro-optic control at a 1 $μ$m pitch. Identical arrays steer light to 53.5$^\circ$ or 32.4$^\circ$, with the angle set by the bias pattern rather than antenna geometry. We measure 18.0% 0th-order modulation depth, 0.09% of incident power in the steered order, and a 940 MHz detected modulation bandwidth. Mode-overlap analysis shows how inter-element coupling limits usable Q, providing design rules for compact, high-speed beam steering.

physics.optics↗

arXiv2025

GHz-speed wavefront shaping metasurface modulators enabled by resonant electro-optic nanoantennas

Electrically tunable metasurfaces that control the amplitude and phase of light through biasing of nanoscale antennas present a route to compact, sub-micron thick modulator devices. However, most platforms face limitations in bandwidth, absolute optical efficiency, and tuning response. Here, we present electro-optically tunable metasurfaces capable of both GHz amplitude modulation and transmissive wavefront shaping in the telecom range. Our resonant electro-optic nanoantenna design consists of a silicon nanobar atop thin-film lithium niobate, with gold electrodes. The silicon nanobar is a periodically perturbed optical waveguide that supports high quality factor (Q $>$ 1000) guided mode resonances excited with free space light. Applying a voltage bias to the lithium niobate tunes its refractive index, modulating the resonant behavior of the silicon nanobar through evanescent mode overlap. We demonstrate an absolute transmittance modulation of 7.1% with $\pm$5 V applied voltage, and show the dependence of this modulation behavior on the resonance quality factor. We additionally study the electrode limitations on modulation bandwidth, demonstrating bandwidths exceeding 800 MHz. Finally, we show how this resonant antenna platform can be used to design wavefront shaping metasurfaces. We demonstrate a beamsplitting metasurface device, whose diffraction efficiency can be modulated with a bandwidth of 1.03 GHz. The high-speed modulation and wavefront control capabilities of this platform provide a foundation for compact, high bandwidth free space communications and sensing devices.

physics.optics↗