All-dielectric quasi-BIC metasurface with strong coupling control by adjusting the loss—potential for vibrational strong coupling

Vibrational strong coupling (VSC) has promising applications in chemical reactions, molecular spectroscopy, and biochemical sensing. VSC can be achieved using plasma nanostructures. However, effective coupling between plasma nanostructures and molecules is often hindered by the metal materials used. Dielectric metasurfaces offer significant advantages and can effectively excite VSC, but the implementation of VSC through dielectric metasurfaces has not been widely investigated. Here, a mid-infrared all-dielectric metasurface to realize strong coupling control driven by quasi-bound states in the continuum (QBIC) is proposed. By coupling with polymethyl methacrylate (PMMA) molecules, a significant spectral splitting occurred. A 50-nm-thick PMMA layer increases the molecular signal amplification factor to 91%. Adjusting structural asymmetry parameters and utilizing the high Q factor of the QBIC mode allows flexible modulation of the coupling state. A strong coupling phenomenon is also observed with an oscillator absorption strength (Δε) 0.02 and a 5 nm PMMA thickness. Refractive index sensing analysis indicates a sensitivity of 2118 nm RIU−1, with a maximum figure of merit of 4089 RIU−1. This study highlights the potential of vibrational strong coupling for advancing biochemical sensing and polaritonic chemistry applications.