A high-performance multi-wavelength optical switch based on multiple Fano resonances in an all-dielectric metastructure

The multi-wavelength optical switch based on an all-dielectric metastructure consisting of four asymmetric semi-circular rings was designed and analyzed in this paper. Four Fano resonance modes, which can be explained by bound states in the continuum (BIC) theory, are excited in our structure with a maximum Q-factor of about 2 450 and a modulation depth close to 100%. By changing the polarization direction of the incident light, the transmission amplitude of Fano resonances can get effectively modulated. Based on this tuning property, the metastructure can achieve a multi-wavelength optical switch in the near-infrared region (900–980 nm) and the maximum extinction ratio can reach 38.3 dB. In addition, the results indicate that the Fano resonances are sensitive to the changes in the refractive index. The sensitivity (S) and the figure of merit (FOM) are 197 nm/RIU and 492 RIU−1. The proposed metastructure has promising potential in applications such as optical switches, sensors, modulators and lasers.