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

• A C2 asymmetry four-leaf clover structure is proposed to introduce the quasi-BIC. • The maximum quality factor and figure of merit are 10,383 and 2250RIU -1 , respectively. • The response of the structure to polarized light is explored. • The multipole excitation mode is analyzed by multipole decomposition method. 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 C 2 asymmetric induced quasi-bound states in the continuum(quasi-BIC). Firstly, we obtain dual Fano resonance by C 2 symmetric configuration. Secondly, by introducing C 2 asymmetric parameters, leading to a new Fano resonance peak, and the Q-factor exceeds 10 4 . 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 .