Mid-infrared high performance dual-Fano resonances based on all-dielectric metasurface for refractive index and gas sensing

The attainment of dual-resonance boasting high Q-factors in the mid-infrared spectrum stands as a captivating domain of inquiry. In this paper, a square nanoblock octamer all-dielectric metasurface is proposed. It generates dual-band responses in the mid-infrared band, exhibiting exceptional Q-factors of up to 15,149 and 120,856 respectively. The data evince a remarkable alignment between the Q -factor derived from fitting the Fano resonances and that computed through FWHM. Multipole decomposition and electromagnetic field distributions indicate dual-resonance modes are controlled by toroidal dipole (TD) and magnetic dipole (MD). The maximum sensitivity to the refractive index is 3666 nm/RIU, the maximum FoM is 55,302 RIU -1 , and the polarization is insensitive. Gas sensors can be developed by filling the metasurface structure with hydrogen and methanesensitive films. This sensor has a maximum sensitivity of -1.304 nm/% for hydrogen and -8.917 nm/% for methane. This research provides an important and effective approach to achieving high -performance midinfrared refractive index, hydrogen, and methane sensor devices.