Nitride–Silver Hybrid PCF-SPR Biosensor: A High-Sensitivity Platform for Synchronous Monitoring of Low-Concentration Analytes and Temperature

This study proposes a dual-parameter photonic crystal fiber-based surface plasmon resonance (SPR) sensor for simultaneous refractive index and temperature detection. The sensor architecture incorporates an asymmetric air hole lattice, featuring elliptical inner holes (aspect ratio: 1.5) to enhance birefringence and axially aligned outer circular holes to optimize surface plasmon coupling. Horizontally, symmetrically deposited silver films and silicon nitride layers constitute the RI-sensing channel, while a vertically machined PDMS-coated silver-nitride structure enables temperature responsivity. The temperature-sensing channel delivers a sensitivity of 20 nm/°C within 0-100 °C, while the RI channel achieves a peak sensitivity of 18,600 nm/RIU across <i>n_a</i> = 1.33-1.41 with a resolution of 5.38 × 10^-6 RIU. Notably, cross-sensitivity between the two channels remains below 5%, underscoring the sensor's capability for independent dual-parameter analysis. This low-interference, high-sensitivity platform holds significant promise for advanced biosensing applications requiring real-time multiparametric monitoring.