Strongly enhanced light-matter coupling of a monolayer WS2 from a bound state in the continuum

TL;DR

This paper demonstrates a significant enhancement of light-matter coupling at room temperature by coupling monolayer WS2 excitons to a bound state in the continuum (BIC), enabling large nonlinearities and robust polariton devices.

Contribution

It introduces a novel architecture that maximizes coupling between monolayer WS2 and a BIC, achieving record Rabi splitting and enabling room temperature nonlinearities.

Findings

Achieved 70 meV Rabi splitting in monolayer WS2-BIC system.

Realized large room temperature optical nonlinearities.

Optimized grating geometry for maximal electric field at the monolayer.

Abstract

Optical bound states in the continuum (BIC) allow to totally prevent a photonic mode from radiating into free space along a given spatial direction. Polariton excitations derived from the strong radiation-matter interaction of a BIC with an excitonic resonance inherit an ultralong radiative lifetime and significant nonlinearities due to their hybrid nature. However, maximizing the light-matter interaction in these structures remains challenging, especially with 2D semiconductors, thus preventing the observation of room temperature nonlinearities of BIC polaritons. Here we show a strong light-matter interaction enhancement at room temperature by coupling monolayer WS2 excitons to a BIC, while optimizing for the electric field strength at the monolayer position through Bloch surface wave confinement. By acting on the grating geometry, the coupling with the active material is maximized in an open and flexible architecture, allowing to achieve a 100 meV photonic bandgap with the BIC in a local energy minimum and a record 70 meV Rabi splitting. Our novel architecture provides large room temperature optical nonlinearities, thus paving the way to tunable BIC-based polariton devices with topologically-protected robustness to fabrication imperfections.