# Infrared hyperbolic metasurface based on nanostructured van der Waals materials

## TL;DR

This paper demonstrates a mid-infrared hyperbolic metasurface created by nanostructuring hexagonal boron nitride, enabling visualization of hyperbolic polaritons and opening new avenues for compact photonic devices.

## Contribution

It introduces a novel hyperbolic metasurface based on nanostructured van der Waals materials and visualizes polariton wavefronts using infrared nanoimaging.

## Key findings

- Visualization of anomalous wavefronts of polaritons
- Nanostructured van der Waals materials support hyperbolic dispersion
- Potential for compact infrared photonic devices

## Abstract

Metasurfaces with strongly anisotropic optical properties can support deep subwavelength-scale confined electromagnetic waves (polaritons) that promise opportunities for controlling light in photonic and optoelectronic applications. We develop a mid-infrared hyperbolic metasurface by nanostructuring a thin layer of hexagonal boron nitride supporting deep subwavelength-scale phonon polaritons that propagate with in-plane hyperbolic dispersion. By applying an infrared nanoimaging technique, we visualize the concave (anomalous) wavefronts of a diverging polariton beam, which represent a landmark feature of hyperbolic polaritons. The results illustrate how near-field microscopy can be applied to reveal the exotic wavefronts of polaritons in anisotropic materials, and demonstrate that nanostructured van der Waals materials can form a highly variable and compact platform for hyperbolic infrared metasurface devices and circuits.

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Source: https://tomesphere.com/paper/1904.03945