Theoretical study of a broadband dual-channel sensor based on sodium-based SPR

Abstract

For wavelength-modulated surface plasmon resonance (SPR) sensors, bandwidth is an essential factor limiting sensor performance. Wide sensing bandwidth is a prerequisite for a dual-channel sensor with high sensitivity and wide detection range. To improve the performance of the dual-channel sensor, we propose a wide-bandwidth photonic crystal fiber (PCF) sensor based on the sodium-coated SPR effect. The substrate of the proposed sensor is a commercial PCF with air holes arranged in a hexagonal pattern and two planes introduced in the cladding by polishing. A sodium film and Polymethyl methacrylate are deposited in the upper plane to form a refractive index sensing channel. A sodium film and Polydimethylsiloxane are deposited in the lower plane to form a temperature sensing channel. The performance of the sensor was analyzed by the finite element method, and the bandwidth of the sensor covers the wavelength range of 600–1700 nm owing to the low intrinsic loss of the sodium film. Numerical results show that the maximum spectral sensitivity of the sensor is 8700 nm/RIU and 20.20 nm/°C when the refractive index of the analyte is 1.330–1.410, and the temperature is 0–50 °C, respectively. The results also show that the sensitivity of the sensor is insensitive to minor changes in structural parameters. Therefore, the sensor is easy to fabricate. Our study provides a theoretical and analytical basis for preparing sodium-based SPR sensors, which have good prospects for applications in the fields of biochemical detection and environmental monitoring.