High Q-factor multiple Fano resonances induced by bound states in the continuum based on all-dielectric nanoholes arrays

Multiple Fano resonances have become an effective means to design optical devices in all-dielectric metasurface. A silicon array-based metasurface structure is proposed in this paper, in which a silicon layer is placed on a silica substrate. Each unit structure is a cube with a square cross section and two half-cylinder etched holes with a cuboid etched hole in the middle. Asymmetry was created by changing the radius of one of the two half-cylinders, resulting in a tunable quasi- BIC mode. As a result, two new Fano peaks with Q values more than 10000 have been discovered, reaching 1.3×10⁴ and 1.5×10⁴ respectively. The highest sensitivity is calculated to be 277.5nm/RIU, while the maximum FOM value is 1387.5, indicating good sensing performance. It is believed that the proposed structure can provide inspiration for the applications of nonlinear optics, optical switches and biochemical sensors.