High-performance MIM waveguide refractive index sensor based on Fano resonance with a cross-shaped concave rectangular structure

Abstract A novel surface plasmon polariton (SPP) refractive index sensor is proposed in this paper. In this sensor, the input and output waveguides are separated by a metal barrier, and a cross-shaped concave rectangular resonator (CCRR) is placed above the waveguides. Two sharp and independently adjustable Fano resonance peaks are observed in the transmission spectrum. The principle of generating Fano peaks is based on the Fano resonance effect, which is excited by the coupling between the CCRR and the metal barrier. The performance of the proposed structure has been studied using the finite element method (FEM). The CCRR structure can generate two independently adjustable Fano resonance peaks, achieving a sensitivity of 1550 nm RIU −1 and a figure of merit (FOM) of 73.8, which demonstrates its broad application potential in high-precision micro-nano sensing. This work provides valuable insights for the subsequent design of sensor structures based on the Fano resonance principle. Moreover, the proposed structure can have wide research and application in high-precision micro-nano sensing, band-stop filtering, and slow-light devices.