High-Q mid-infrared fano metasurface biosensor based on toroidal dipole resonance

Abstract

This article presents a metasurface biosensor exhibiting a Fano resonance with ultra-high quality factor (Q) up to 153,789. Field distribution and multipole decomposition reveal that the sharp Fano resonance originates from a toroidal dipole mode. The metasurface demonstrates polarization-independent response, enhancing operational robustness in practical biosensing scenarios. Numerical simulations are conducted to detect different types of amino acids, blood samples infected with Mycobacterium tuberculosis, and malaria-affected red blood cells (RBCs). The results show that the sensor can achieve maximum sensitivity of 4.084 μm/RIU and figure of merit (FOM) of 73,781. This research highlights the metasurface's great potential for label-free biosensing applications while providing a theoretical foundation for high-Q factor sensor design.