Research and Application of Multiple Fano Peaks in the Mid-Infrared Band of All-Dielectric Metasurfaces With a Sunken Step-Style Groove

The intrinsic loss associated with metals is avoided by an all-dielectric metasurface, enabling a higher Q-factor to be achieved. In this study, multiple Fano resonances are generated by a metasurface designed with an all-dielectric array, facilitating four applications in the mid-infrared (MIR) band, namely, refractive index sensing, temperature sensing, fingerprint detection, and optical switching. Particularly noteworthy is refractive index sensing, which achieves a figure of merit of up to 8809.756 RIU<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-{1}}$ </tex-math></inline-formula> and a high Q magnitude of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{{5}}$ </tex-math></inline-formula>. A sensitivity of 263.8 pm/°C is attained for temperature sensing, indicating good sensing performance. Toluene (C7H8) and blood were effectively detected via fingerprint detection. The nanoarray cell primarily comprises a sunken step-style groove, enabling both in-plane and out-of-plane asymmetry and facilitating application to the quasi-continuous domain-bound state (q-BIC). These high and low structural dropouts enable the metasurface to form multiple Fano resonances and respond differently to transverse electric (TE) and transverse magnetic (TM) polarized light. A multipole decomposition of the resonance peaks was conducted to investigate the formation mechanism of the resonance peaks. The incorporation of in-plane and out-of-plane asymmetry, in addition to its multifaceted applications within a single metasurface, enhances the informational richness of metasurface designs.