# Exciton-polaritons in multilayer WSe$_2$ in a planar microcavity

## TL;DR

This study demonstrates strong exciton-photon coupling in multilayer WSe$_2$ flakes within a tunable planar microcavity, revealing layer-dependent effects and potential for advanced light-matter interaction applications.

## Contribution

It provides the first experimental observation of strong coupling in multilayer WSe$_2$ within a tunable microcavity, including both monolayer and few-layer samples.

## Key findings

- Strong coupling observed in monolayer WSe$_2$
- Strong coupling also observed in few-layer WSe$_2$
- Cavity mode energy tunable by 150 meV

## Abstract

Due to high binding energy and oscillator strength, excitons in thin flakes of transition metal dichalcogenides constitute a perfect foundation for realizing a strongly coupled light-matter system. In this paper we investigate mono- and few-layer WSe$_2$ flakes encapsulated in hexagonal boron nitride and incorporated into a planar dielectric cavity. We use an open cavity design which provides tunability of the cavity mode energy by as much as 150 meV. We observe a strong coupling regime between the cavity photons and the neutral excitons in direct-bandgap monolayer WSe$_2$, as well as in few-layer WSe$_2$ flakes exhibiting indirect bandgap. We discuss the dependence of the exciton's oscillator strength and resonance linewidth on the number of layers and predict the exciton-photon coupling strength.