Harnessing dielectric metasurfaces for light-matter interactions in the infrared region

Resonant metasurfaces exhibit exceptional subwavelength light-trapping capabilities crucial for advanced biochemical sensors and surface-enhanced spectroscopy. While mid-infrared light-matter interactions have predominantly operated in the weak coupling regime, exploring the strong coupling regime—marked by hybrid polariton states—remains underexplored. Notably, low-loss dielectric metasurfaces with quasi-bound states in the continuum (q-BIC) offer ideal platforms for coherent energy exchange between their high-Q cavities and molecular resonances. This study delves into q-BIC resonances at mid-infrared wavelengths identifying key parameters governing the transition from weak to strong coupling. Moreover, we introduce a novel transitional coupling zone where polaritons are challenging to spectrally distinguish. Additionally, we analyze molecules' transition dipole strength, damping rate, and the total number of molecules coupled to a single cavity, offering insights to optimize dielectric metasurfaces for VSC. These findings provide crucial guidelines for enhancing VSC across diverse molecular transitions, anticipating transformative impacts on polaritonic chemistry.