Low crosstalk dual-parameter no-core fiber based SPR sensor with differentiated silver film thickness

Due to the limitation of the surface plasmon resonance (SPR) sensing band, the resonance wavelength range of dual-parameter sensing is relatively narrow. To solve this problem, we propose the broadband SPR dual-parameter sensor with differentiated silver film thickness. The sensor can simultaneously measure temperature and refractive index (RI). The effect of the silver film thickness on the SPR sensing band is experimentally investigated. The results show that the SPR sensing band redshifts with increasing silver film thickness. Therefore, depositing different thicknesses of silver films on the outer surface of coreless fiber can increase the resonance wavelength range of sensing probes and reduce the crosstalk between the two dips. During the experiments, it was determined that a combination of silver films with 50 nm and 70 nm thickness could maximize the bandwidth of the SPR dual-paremeter sensor. The test results show that the sensor has a maximum RI sensitivity of 3060 nm/RIU and a 1.333-1.375 RI measurement range. The sensor has a maximum temperature sensitivity of 4.3 nm/°C and a 10-80 °C measurement range. In addition, the sensor has an excellent stability. This method of broadening the resonance wavelength range is simple and effective and has potential applications in multiparameter measurements.