# Photonic-Crystal Exciton-Polaritons in Monolayer Semiconductors

## TL;DR

This paper demonstrates a compact, tunable photonic crystal platform for strong exciton-photon coupling with monolayer semiconductors, enabling room-temperature polariton phenomena and flexible device engineering.

## Contribution

It introduces sub-wavelength photonic crystals integrated with monolayer semiconductors for strong coupling, offering enhanced control and room-temperature operation.

## Key findings

- Room-temperature polariton dispersions measured.
- Suppressed non-radiative decay to dark excitons.
- Anisotropic dispersions and Fano resonances observed.

## Abstract

Semiconductor microcavity polaritons, formed via strong exciton-photon coupling, provide a quantum many-body system on a chip, featuring rich physics phenomena for better photonic technology. However, conventional polariton cavities are bulky, difficult to integrate, and inflexible for mode control, especially for room temperature materials. Here we demonstrate sub-wavelength thick one-dimensional photonic crystals (PCs) as a designable, compact and practical platform for strong coupling with atomically thin van der Waals Crystals (vdWCs). Polariton dispersions and mode anti-crossings are measured up to room temperature. Non-radiative decay to dark excitons was suppressed due to polariton enhancement of the radiative decay. Unusual features, including highly anisotropic dispersions and adjustable Fano resonances in reflectance, may facilitate high temperature polariton condensation in variable dimensions. Combining slab PCs and vdWCs in the strong coupling regime allows unprecedented engineering flexibility for exploring novel polariton phenomena and device concepts.