Dual-parameter fiber optic surface plasmon resonance sensor with narrow FWHM based on an incidence angle adjusting method

We propose a dual-parameter surface plasmon resonance (SPR) sensor based on a simple, and effective incidence angle adjustment method. It is capable of simultaneously detecting the refractive index and temperature of a liquid. For conventional SPR fiber sensors, the resonance dip will be abnormally broadened in the near-infrared band, leading to difficulty in identifying the SPR dip by the spectrometer. The FWHM of the resonance dip depends on the SPR intensity. Therefore, we propose to utilize the bubble structure to change the incidence angle, which can enhance SPR intensity and thus reduce the FWHM of the resonance dip. During our experiments, we investigated the modulation effect of bubble size on the SPR effect. Subsequently, a two-parameter sensor with a narrow FWHM was prepared using PDMS, and the experimental results show that no crosstalk exists between the two sensing channels. This sensor is beneficial for improving the FWHM of SPR dip.