Cascaded dual-channel broadband SPR fiber optic sensor based on Ag/ZnO and Ag/TiO2/PDMS films structure

In order to broaden the bandwidth of SPR dual-channel sensors, this work proposes to tune the resonance wavelength range of the sensors using a cascade of ZnO and TiO2 films. The two oxides are transversely deposited on Ag-based no-core fiber to form a dual-channel sensor that can be used for refractive index (RI) and temperature measurements. Among them, Ag/ZnO is used for RI sensing and Ag/TiO2/PDMS is used for temperature sensing. The simulation and experimental results show that ZnO and TiO2 have the effect of broadening the resonance wavelength range by 44 nm and 72 nm, respectively. In addition, when the two oxides are added to the Ag-based sensor, the SPR valley is red-shifted, and the sensitivity is enhanced. The experimental results also show that the two oxides make the silver film less susceptible to oxidation and enhance the stability of the sensor. Numerical results show that the maximum RI sensitivity of the sensor is 4630 nm/RIU, and the temperature sensitivity is 5.8 nm/°C. The range of the object to be measured is 1.333–1.385, 0–50 °C. This ability to broaden the sensor bandwidth provides a new direction for designing and applying high-performance multi-channel SPR sensors.