Negative refraction of ultra-squeezed in-plane hyperbolic designer polaritons

TL;DR

This paper demonstrates the first experimental observation of in-plane negative refraction of ultra-squeezed hyperbolic designer polaritons using hyperbolic metasurfaces, achieving record-breaking squeezing factors and enabling deep-subwavelength nanophotonic applications.

Contribution

It introduces a novel class of hyperbolic metasurfaces supporting high-momentum polaritons and reports the first experimental observation of all-angle negative refraction at deep-subwavelength scales.

Findings

First experimental observation of negative refraction of designer polaritons.

Record-breaking squeezing factor up to 129.

Hyperbolic metasurfaces support ultra-high-k polaritons with hyperbolic dispersion.

Abstract

The in-plane negative refraction of high-momentum (i.e., high-k) photonic modes could enable many applications such as imaging and hyperlensing in a planar platform at deep-subwavelength scales. However, its practical implementation in experiments remains elusive so far. Here we propose a class of hyperbolic metasurfaces, which is characterized by an anisotropic magnetic sheet conductivity and can support the in-plane ultrahigh-k magnetic designer polaritons. Based on such metasurfaces, we report the first experimental observation of the all-angle negative refraction of designer polaritons at extremely deep-subwavelength scales. Moreover, we directly visualize the designer polaritons with hyperbolic dispersions. Importantly, for these hyperbolic polaritons, we find that their squeezing factor is ultra-large and, to be specific, it can be up to 129 in the experiments, a record-breaking value exceeding those in naturally hyperbolic materials. The present scheme for the achievement of negative refraction is also applicable to other natural materials and may enable intriguing applications in nanophotonics. Besides, the proposed metasurfaces are readily tailorable in space and frequency, which could serve as a versatile platform to explore the extremely high confinement and unusual propagation of hyperbolic polaritons.