Ultra-sensitive hexagonal PCF-SPR sensor with a broad detection range

A photonic crystal fibre (PCF) sensor based on surface plasmon resonance (SPR) with a hexagonal structure and external gold coating is designed and demonstrated to have a broad detection range and ultra-high sensitivity. Gold is chosen as the plasmonic materials due to the inert and stable chemical properties and the gold coating on the PCF-SPR sensor also simplifies the detection and fabrication processes. The sensing properties are analysed by the finite element method (FEM). In this sensor, the y-polarized mode with the large mode field area shows better performance such as the high spectral sensitivity of 28,700 nm/RIU, wide analyte refractive index (RI) range from 1.28 to 1.43, resolution of 3.48×10^-6 RIU, and maximum amplitude sensitivity of 2481.06 RIU⁻¹. Furthermore, the paragon figure of merit and signal-to-noise ratio of the sensor are 517.81 RIU⁻¹ and 5.18, respectively.