Visible-NIR Surface Plasmon Resonance Sensing Technology for High-Sensitivity RI and Temperature Simultaneous Detection

Since the development of surface plasmon resonance (SPR) sensors in the visible wavelength band has encountered a bottleneck, we propose to excite the SPR effect in the near-infrared (NIR) wavelength band. In this work, we utilize ZnO with a high dielectric constant to modulate the SPR effect. Experimental results show that ZnO can induce a redshift in the SPR effect, and the degree of redshift is proportional to the thickness of the ZnO film. We give a corresponding physical explanation for this and utilize this phenomenon to prepare a dual-parameter sensor that can work simultaneously in the visible and NIR. With a bandwidth of 500–1400 nm, the sensor enables simultaneous detection of the refractive index and temperature of liquids. The sensor has a photonic crystal fiber (PCF) as the substrate, a silver film as the excitation layer, and a ZnO film as the modulation layer. We conducted dual-parameter sensing experiments on it, and the experimental results show that the maximum sensitivity of this sensor is 9135 nm/RIU and 8.68 nm/°C in the range of RI of 1.333–1.420 and temperature of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0~^{\circ }$ </tex-math></inline-formula> C–<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$70~^{\circ }$ </tex-math></inline-formula> C, respectively. In addition, we verified that the dual-parameter sensor has good repeatability and stability through repeatability experiments. This work demonstrates the feasibility of simultaneous excitation of the SPR effect in the visible and NIR wavelength bands. This study significantly improves the narrowband problem of previous multichannel sensors and promotes the development of SPR sensing technology to the NIR band.