Core-mismatched SPR temperature sensor based on silver and PDMS films

Abstract

Surface plasmon resonance (SPR) sensors show great potential in practical applications of concentration and temperature measurement due to their high sensitivity and fast response speed. However, the cumbersome probe preparation process is still a significant problem faced by fiber SPR technology. Here, we propose a simple and rapid method for the fabrication of sensing probes. In this study, the silver mirror reaction was used to coat the silver film on the surface of a core mismatch fiber structure formed by a single-mode fiber (SMF) and two multimode fibers (MMF) to excite the SPR, The core mismatch sensing element is prepared by cleaving and fusion splicing, and the coating of the sensing film adopts a simple silver mirror reaction, so the preparation process is extremely simple. After the silver film is uniformly coated on the single-mode fiber sensing unit, the sensing unit was immersed in polydimethylsiloxane (PDMS) and cured by heating for temperature sensing measurement. Thanks to the higher thermo-optic coefficient, the refractive index of PDMS on the sensor probe will also change when the external temperature changes, so the surface plasmon resonance dip underwent a noticeable wavelength shift. Further, the cured PDMS can also enhance the stability of the probe structure. The results show that in the temperature range of 20℃ to 80℃, the maximum temperature sensitivity is -1.66nm/℃, with good stability, accuracy and repeatability. In addition, the sensor has the advantages of simple structure, convenient fabrication, good reversibility and strong stability. The temperature sensor based on core mismatch is expected to be used in the temperature detection of fields such as biology, medical treatment, and aerospace.