Micro-rectangular grooved D-shaped PCF-SPR temperature sensor

Abstract A D-shaped micro-rectangular channel photonic crystal fiber (PCF) based high-sensitivity surface plasmon resonance (SPR) temperature sensor is proposed and designed in this work. Silver (Ag) is utilized as the plasmonic material, and titanium dioxide (TiO 2 ) is introduced as both an anti-oxidation protective layer and a sensitivity-enhancing layer. The SPR effect is excited by depositing a bilayer Ag/TiO 2 film within the D-shaped micro-rectangular channel. Polydimethylsiloxane (PDMS), which exhibits a negative thermo-optic coefficient, is selected as the temperature-sensitive filling material. The coupling characteristics between the fundamental core mode and the surface plasmon polariton (SPP) mode were numerically analyzed using the finite element method (FEM). Key structural parameters, including the type and thickness of the metal film, air hole diameter, and pitch, were systematically optimized through a variable-controlled approach. Simulation results demonstrate that the sensor exhibits excellent performance over a broad detection range of 10 °C–130 °C, achieving a high linear correlation coefficient (R 2 ) of 0.99972. The sensor demonstrates an ultra-high wavelength sensitivity of 42.5 nm °C −1 , achieving an exceptional temperature resolution of 0.0023 °C. The proposed structure features a simplified design, high sensitivity, and robust fabrication tolerance, making it a promising candidate for real-time biomedical and environmental monitoring applications.