Tailoring Quasi-BIC States in Liquid Crystal-Integrated WS₂ Nanostructured Metasurfaces for Tunable High Q-Factor Optoelectronic Devices

This study explores light-matter interactions in nanostructured WS 2 metasurfaces integrated with a liquid crystal (LC) medium using numerical simulations. Transition metal dichalcogenides (TMDCs), particularly WS 2 and MoS 2, are known for their strong excitonic effects as well as trapped photons via quasi-bound states in the continuum (quasi-BIC) and anapoles. Many investigations recently are directed towards hybrid WS 2 + dielectric metasurfaces, in which coupling between excitons in WS 2 and quasi-BIC states formed in dielectric metasurfaces are studied. In contrast, our research in this article focuses on the tunability of quasi-BIC states by embedding nanostructured WS 2 metasurfaces in a liquid crystal (LC) medium, which can be easily controlled using external fields. Our study finds that LC reorientations give rise to splitting of quasi-BIC states into multiple modes. It was observed that in-plane LC reorientations lead to crossing behavior between electric and toroidal dipole modes, while the magnetic dipole seems to be the dominant mode across the investigated frequency range. These results are confirmed using mode analysis, far-field, and near-field radiation patterns. These findings suggest that LC-based tuning of quasi-BIC states could enable advancements in tunable optoelectronic, excitonic, and valleytronic devices, with potential applications in next-generation wearable optoelectronics devices.