Multimodal ultra-high Q-factor C2 asymmetric all-dielectric metasurface induced by quasi-BIC states

Abstract

A high Q-factor resonant cavity indicates minimal energy loss at the resonance frequency. In this paper, we propose a four-leaf clover sensor with air pillars based on the all-dielectric metasurface and discuss the C2 asymmetric induced quasi-bound states in the continuum(quasi-BIC). Firstly, we obtain dual Fano resonance by C2 symmetric configuration. Secondly, by introducing C2 asymmetric parameters, leading to a new Fano resonance peak, and the Q-factor exceeds 104. Furthermore, When the incident laser changes from TE mode to TM mode, the original Fano resonance peaks gradually disappear, and a new peak is generated near the 1273 nm. The calculated polarization sensitivity is up to 0.012 per degree. The dynamic range (DR) of the peak value of transmission spectrum with polarization is 58 dB. By calculation, we have achieved a maximum sensitivity (S) of 270 nm/RIU for an optical refractive index sensor, with a figure of merit (FOM) value of 2250 RIU-1.