Single-gate electro-optic beam switching metasurfaces

TL;DR

This paper introduces a single-gate electro-optic metasurface capable of active beam switching with high directivity and efficiency, simplifying control mechanisms compared to traditional multi-gate designs.

Contribution

The work demonstrates a novel single-gate metasurface device for active beam switching, offering high directivity and efficiency with a simplified control scheme.

Findings

Achieved 57° beam switching from 0th to -1st order

Demonstrated efficiencies of approximately 8%

Provided an analytical framework for understanding the mechanism

Abstract

Electro-optic active metasurfaces have attracted attention due to their ability to electronically control optical wavefront with unprecedented spatiotemporal resolutions. In most studies, such devices require gate arrays composed of a large number of independently-controllable local gate electrodes that address local scattering response of individual metaatoms. Although this approach in principle enables arbitrary wavefront control, the complicated driving mechanism and low optical efficiency have been hindering its practical applications. In this work, we demonstrate an active beam switching device that provides high directivity, uniform efficiency across diffraction orders, and a wide field of view while operating with only a single-gate bias. Experimentally, the metasurface achieves 57{\deg} of active beam switching from the 0th to the -1st order diffraction, with efficiencies of 0.084 and 0.078 and directivities of 0.765 and 0.836, respectively. Furthermore, an analytical framework using nonlocal quasinormal mode expansion provides deeper insight into the operating mechanism of active beam switching. Finally, we discuss the performance limitations of this design platform and provide insights into potential improvements.