Polaritonic Critical Coupling in a Hybrid Quasi-Bound States in the Continuum Cavity-WS$_2$ Monolayer System

TL;DR

This paper theoretically and numerically demonstrates a hybrid cavity-WS$_2$ monolayer system achieving polaritonic critical coupling, enabling full electromagnetic energy transfer and controlled polariton population for potential light-emitting applications.

Contribution

It introduces the concept of polaritonic critical coupling in a hybrid metasurface-WS$_2$ system, revealing how damping rates control strong and critical coupling conditions.

Findings

Polaritonic critical coupling occurs when cavity and excitonic damping rates are equal.

Asymmetry in quasi-bound states tunes polariton population.

Full electromagnetic energy transfer is achieved at critical coupling.

Abstract

We theoretically propose and numerically demonstrate that perfect feeding of a polaritonic system with full electromagnetic energy under one-port beam incidence, referred to as polaritonic critical coupling, can be achieved in a hybrid dielectric metasurface-WS$_2$ monolayer structure. Polaritonic critical coupling, where the critical coupling and strong coupling are simultaneously attained, is determined by the relative damping rates of the cavity resonance, $\rm \gamma_Q$, provided by a symmetry-protected quasi-bound states in the continuum, and excitonic resonance of WS$_2$ monolayer, $\rm \gamma_X$. We reveal that the population of the polariton states can be tuned by the asymmetric parameter of the quasi-bound states in the continuum. Furthermore, polaritonic critical coupling is achieved in the designed system while $\rm \gamma_Q=\gamma_X$ and only strong coupling is achieved while $\rm \gamma_Q\neq\gamma_X$. This work enriches the study of polaritonic physics with controlled absorbance and may guide the design and application of efficient polariton-based light-emitting or lasing devices.