Single-channel SPRbased mode-division-multiplexing weakly coupled few-mode PCF sensor for simultaneous dual-parameter detection

Purpose This study aims to simultaneously achieve high sensitivity in both temperature and refractive index (RI) sensing, a weakly coupled few-mode photonic crystal fiber-based surface plasmon resonance (FM-PCF-SPR) sensor using mode-division multiplexing technology is proposed theoretically. Design/methodology/approach The proposed weakly coupled few-mode photonic crystal fiber (FM-PCF) is designed to support two linearly polarized (LP) modes (LP01 and LP11) with a minimum effective RI difference of 0.00147, enabling dual-parameter simultaneous sensing. The cladding structure of the proposed weakly coupled FM-PCF consists of two outermost layers arranged in a hexagonal air hole configuration. In addition, the innermost layer of air holes is arranged in a circular shape to enhance the fiber core’s confinement capability. The central hole of the PCF is filled with the analyte, whereas the rightmost hole of the inner layer is coated with metal to excite surface plasmon polariton modes. The optical properties of the proposed weakly coupled FM-PCF-SPR sensor are investigated using the finite element method. Findings Numerical analysis results indicate that the sensor achieves a maximum sensitivity of 25,000 nm/RIU for RI detection within the range of 1.38–1.42 using the LP01 mode, and 10 nm/°C for temperature detection within the range of 50°C–110°C using the LP11 mode. The proposed sensor with enhanced sensitivity holds promising potential for a wide range of applications in life sciences research, chemical production and environmental monitoring. Originality/value This work underscores a study of dual-parametric sensing in a single physical channel by using two modes, LP01 and LP11, of weakly coupled FM-PCFs.