Dual-Channel SPR Temperature Sensor Based on Side-Polished Hollow Core Fiber and PDMS

This paper presents a dual-channel surface plasmon resonance (SPR) temperature sensor with an adjustable detection range. We employ a side-polished hollow core fiber (HCF) filled with polydimethylsiloxane (PDMS), with a 50-nm gold film coated on both HCF and PDMS. To further improve sensor performance, a 30-nm-thick Ge₂ Sb₂ Te₅ (GST) is coated on the outer surface of the gold film. The GST film increases the dielectric constant of the metal film, thereby enhancing the sensitivity. The structure of the sensor allows for precise temperature change detection, as the refractive index (RI) of PDMS is highly sensitive to temperature-induced changes. Two separated resonance dips, which are related to the two channels, are observed at different wavelengths in the transmission spectrum. Notably, the two dips move in opposite directions with the temperature variation. The intervals between the two SPR dips are measured at different ambient temperatures, showing a good linear relationship. The proposed sensor with varying detection ranges is fabricated by altering the RI of the external filling liquid, which is simple and convenient. Experimental results demonstrate excellent sensitivity, with a response of 25.8 nm/°C as the temperature rises from 0 °C to 40 °C, and a response of 24 nm/°C as the temperature increases from 40 °C to 80 °C. The dual-channel SPR sensor exhibits outstanding sensitivity in temperature measurement and is expected to find applications in fields such as thermal management, medical diagnostics, industrial process control, and environmental monitoring.