Nonlocal Electro-Optic Metasurfaces for Free-Space Light Modulation

TL;DR

This paper demonstrates a novel nonlocal electro-optic metasurface using lithium niobate for fast, efficient free-space light modulation with high depth and bandwidth, advancing integrated photonics technology.

Contribution

It introduces a new nonlocal electro-optic metasurface design utilizing resonant waveguide modes in lithium niobate for ultrafast light modulation.

Findings

Achieved up to 42% intensity modulation depth

Operates at 850-950 nm wavelength range

Bandwidth potential of 6.5 GHz

Abstract

Dynamic optical metasurfaces with ultrafast temporal response, i.e., spatiotemporal optical metasurfaces, provide attractive solutions and open fascinating perspectives for modern highly integrated optics and photonics. In this work, electro-optically controlled optical metasurfaces operating in reflection and utilizing resonant waveguide mode excitation are demonstrated from the viewpoint of free-space propagating light modulation. The modulation of reflected light power with superior characteristics in comparison with prior research is achieved by identifying a suitable low-loss waveguide mode and exploiting its resonant excitation. The electro-optic Pockels effect in a 300-nm-thick lithium niobate (LN) film sandwiched between a continuous thick gold film and an array of gold nanostripes, serving also as control electrodes, is exploited to realize fast and efficient light modulation. The fabricated compact (active area <1000 $\mu$m) modulators operate in the wavelength range of 850-950 nm, featuring a maximum intensity modulation depth of $\sim\!$ 42 % at the driving voltage of $\pm$10 V within the bandwidth of 13.5 MHz (with the potential bandwidth of 6.5 GHz). The introduced nonlocal electro-optic metasurface configuration opens new avenues towards the realization of ultrafast, efficient and robust free-space light modulators based on an LN flat optics approach.