Enhanced electro-optic modulation in resonant metasurfaces of lithium niobate

TL;DR

This paper demonstrates a lithium niobate metasurface capable of fast, low-voltage, MHz-range optical modulation, with resonance-enhanced transmission modulation by a factor of 80, advancing free-space photonic device technology.

Contribution

It introduces a resonant lithium niobate metasurface that significantly enhances electro-optic modulation efficiency for free-space applications.

Findings

Resonance enhances transmission modulation by 80 times.

Achieved low-voltage, MHz-speed modulation.

First demonstration of lithium niobate metasurface for free-space modulation.

Abstract

In display technologies or data processing, planar and subwavelength free-space components suited for flat photonic devices are needed. Metasurfaces, which shape the optical wavefront within hundreds of nanometers, can provide a solution for thin and portable photonic devices, e.g. as CMOS-compatible modules. While conventional electro-optic modulators are inconvenient to operate in free space configurations, its principle can largely be applied to the development of active metasurfaces with the prospect of modulation speeds up to the GHz region. Here, we use this concept to realize fast and continuous modulation of light at low voltage and MHz speed with a lithium niobate metasurface tuned by the linear electro-optic effect. Furthermore, we exploit the resonance in the visible to enhance the modulation of the transmitted light by two orders of magnitude, namely by a factor of 80, compared to the unstructured substrate. This proof-of-concept work is a first important step towards the use of lithium niobate metasurfaces for free space modulation.