Refractive index sensing of double Fano resonance excited by nano-cube array coupled with multilayer all-dielectric film

We propose a hybrid structure of a nano-cube array coupled with multilayer full-dielectric thin films for refractive index sensing. In this structure, discrete states generated by two-dimensional grating and continuous states generated by a photonic crystal were coupled at a specific wavelength to form two Fano resonances. The transmission spectra and electric field distributions of the structure were obtained via the finite-difference time-domain method. We obtained the optimal structural parameters after optimizing the geometrical parameters. Under the optimal parameters, the figure of merit (FOM) values of the two Fano resonances reached 1.7×10⁴ and 3.9×10³, respectively. These results indicate that the proposed structure can achieve high FOM refractive index sensing, thus offering extensive application prospects in the biological and chemical fields.