Meta-Optics with Lithium Niobate

TL;DR

This paper reviews recent advances in lithium niobate-based metasurfaces, highlighting their potential for miniaturized nonlinear optical devices, light sources, and quantum optics applications, while discussing current limitations.

Contribution

It provides a comprehensive overview of recent progress in lithium niobate metasurfaces and discusses future prospects and challenges in the field.

Findings

First demonstrations of LN-based metasurfaces achieved

Potential for ultra-flat nonlinear light sources

Applications in quantum optics and light modulation

Abstract

The rapid development of metasurfaces - 2D ensembles of engineered nanostructures - is presently fostering a steady drive towards the miniaturization of many optical functionalities and devices to a subwavelength size. The material platforms for optical metasurfaces are rapidly expanding and for the past few years, we are seeing a surge in establishing meta-optical elements from high-index, highly transparent materials with strong nonlinear and electro-optic properties. Crystalline lithium niobate (LN), a prime material of choice in integrated photonics, has shown great promise for future meta-optical components, thanks to its large electro-optical coefficient, second-order nonlinear response and broad transparency window ranging from the visible to the mid-infrared. Recent advances in nanofabrication technology have indeed marked a new milestone in the miniaturization of LN platforms, hence enabling the first demonstrations of LN-based metasurfaces. These seminal works set the first steppingstone towards the realization of ultra-flat monolithic nonlinear light sources with emission ranging from the visible to the infrared, efficient sources of correlated photon pairs, as well as electro-optical devices. Here, we review these recent advances, discussing potential perspectives for applications in light conversion and modulation shaping as well as quantum optics, with a critical eye on the potential setbacks and limitations of this emerging field.