Liquid Crystal Based Active Tuning of Strong Coupling in WS ₂ Nanostructured Metasurfaces

Strong light-matter interactions in 2D materials have garnered significant interest for their potential in nonlinear optics and quantum photonics. Transition metal dichalcogenides (TMDCs), with their robust excitonic responses, serve as promising materials for exploring these interactions. Notably, the ability to tailor strong coupling for tunable quantum and nonlinear emissions is still underexplored. In this study, we employ liquid crystals (LCs) as a tunable medium to modulate the strong coupling between excitons and trapped photonic modes in WS2 metasurfaces with asymmetric nanostructures. LCs offer high birefringence and anisotropic optical properties, which can be dynamically tuned by using external stimuli such as electric fields or temperature variations. By embedding WS2 structures within an LC medium and coupling them to photonic quasi-bound states in the continuum (quasi-BIC) exhibited by WS2 metasurfaces, we demonstrate precise control over the exciton-photon interactions. The current work extends our earlier report on LC-based tuning of quasi-BIC states as a function of LC orientations and shows that such a dynamic tuning of quasi-BIC states further results in tailoring the strong coupling between excitons and trapped photons. In the current study, self-hybridization in the WS2 metasurfaces exhibit Rabi splitting energy of 182.5 meV in air and 139, 109.6, and 131 meV, with LC orientations along X-, Y-, and Z-axes, respectively. We show that, as a function of LC orientation, multiple spectral splittings are observed in lower and upper branches of Rabi splitting. Our findings establish a versatile platform where TMDCs and LCs synergistically enable electrically controllable strong coupling, offering a scalable and responsive architecture for next-generation quantum photonic devices.