Angle-breaking all-dielectric metasurface optical sensor based on bound states in the continuum

We investigate and analyze the excitation mechanism of multiple Fano resonances based on an angle-breaking all-dielectric metasurface. By introducing a sector defect, the field strength of the excited Fano resonance peak is mainly centered around the sector structure, indicating a quasi-bound state in the continuum (BIC) mode at 1287.97 nm, with a modulation depth of 100%, a Q-factor of 2.23×10⁴, and a maximum figure of merit (FOM) of 4300RIU^-1. Moreover, we study the dispersion relations and near-field distributions of the BIC corresponding to resonance peaks at different wavelengths. Results illustrate that the excited new Fano resonance is mainly dominated by the magnetic dipole (MD). Modifying structural parameters such as the period and semicircular radius can enhance the structure's stability and adaptability. The proposed sensor has great prospects in healthcare, environmental monitoring, and multi-channel biosensing.