Machine learning analysis of a Fano resonance based plasmonic refractive index sensor using U shaped resonators.

Plasmonic sensors have received special consideration for refractive index (RI) measurement due to the benefits of compact footprints and high sensitivities. To fulfill such conditions, a Fano resonance (FR)-based RI sensor using plasmonic nano-structures is designed and analyzed here. The presented topology comprises a metal-insulator-metal waveguide, a U-shaped, and an inverted U-shaped resonator. The transmission spectrum is obtained utilizing the finite-difference time-domain method. Two FRs appear in the transmission spectrum that are suitable options for sensing performance. The best values of two important factors are a sensitivity of 571.4 nm/RIU and a figure of merit of 14,987 RIU^-1 for the first FR (598 nm). Furthermore, the transmittance values at intermediate wavelengths with four geometrical parameters and the RI of the analyte are predicted utilizing the Extreme Randomized Tree regression model. This model is evaluated utilizing an adjusted R square score (Adj-R²S) as an assessment parameter using the value of n_min = 3 and a test case of 10%. The Adj-R²S closes 1, showing that transmittance values can be forecasted with high precision. Applying this method decreases the simulation time and resources by 90%. The presented sensor with machine learning behavior prediction ability can be utilized for RI sensing performance.