Polaritonic critical coupling in a hybrid quasibound states in the continuum cavity–<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>WS</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math> monolayer system
Xia Zhang, A. Louise Bradley
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--${\mathrm{WS}}_{2}$ monolayer structure. Polaritonic critical coupling, where critical coupling and strong coupling are simultaneously attained, is determined by the relative damping rates of the cavity resonance, ${\ensuremath{\gamma}}_{Q}$, provided by a symmetry-protected quasibound states in the continuum cavity, and excitonic resonance of the ${\mathrm{WS}}_{2}$ monolayer, ${\ensuremath{\gamma}}_{X}$. We reveal that the population of the polariton states can be tuned by the asymmetry parameter of the quasibound states in the continuum. Furthermore, polaritonic critical coupling is achieved in the designed system while ${\ensuremath{\gamma}}_{Q}={\ensuremath{\gamma}}_{X}$, and only strong coupling is achieved while ${\ensuremath{\gamma}}_{Q}\ensuremath{\ne}{\ensuremath{\gamma}}_{X}$. 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.