Image polaritons in van der Waals crystals

TL;DR

This review explores the emerging field of image polaritons in van der Waals crystals, highlighting their unique properties, dispersion, and potential for nanoscale light manipulation with lower losses.

Contribution

It systematically reviews the recent advances in understanding and experimental realization of image polaritons in van der Waals materials, a new class of nanophotonic modes.

Findings

Image polaritons enable ultra-compressed optical fields.

They exhibit lower propagation loss than conventional polaritons.

Experimental breakthroughs demonstrate their potential for nanoscale light control.

Abstract

Polaritonic modes in low-dimensional materials enable strong light-matter interactions and provide a platform for light manipulation at nanoscale. Very recently, a new class of polaritons has attracted considerable interest in nanophotonics: image polaritons in van der Waals crystals, manifesting when a polaritonic material is in close proximity to a highly conductive metal, so that the polaritonic mode couples with its mirror image. Image modes constitute an appealing nanophotonic platform, providing an unparalleled degree of optical field compression into nanometric volumes while exhibiting lower normalized propagation loss compared to conventional polariton modes in van der Waals crystals on non-metallic substrates. Moreover, the ultra-compressed image modes provide access to the nonlocal regime of light-matter interaction. In this Review, we systematically overview the young yet rapidly growing field of image polaritons. We discuss their dispersion properties, showcase the diversity of image modes in various van der Waals materials, and highlight the experimental breakthroughs owing to the unique properties of image polaritons.