Low Crosstalk Plastic Optical Fiber-Based Dual-Parameter SPR Sensor With Stepped Side-Polished Structure and Differentiated Au-Film Thickness

In this article, a surface plasmon resonance (SPR) sensor based on a stepped side-polished plastic optical fiber (POF) is proposed and demonstrated for simultaneous measurement of refractive index (RI) and temperature. A differentiated Au-film thickness was deposited on the stepped polished region, which can enlarge the wavelength space for the SPR peaks of RI and temperature sensing channels and reduce their crosstalk. The polydimethylsiloxane (PDMS) film was fabricated on the polished region with a deeper polished depth and a thicker Au-film thickness for temperature sensing. The stepped polished structure can obtain a better resonance peak visibility for the temperature sensing. The experimental results show that the RI sensitivity of the sensor is 1759 nm/RIU in the RI range of 1.335-1.37 and the temperature sensitivity is -0.82 nm/degrees C in the temperature range of 20 degrees C-80 degrees C. The probe has the advantages of easy fabrication and simple structure, which has potential application prospect in the field of biochemical sensing.