Cascaded Dual-Channel Fiber SPR Sensor Based on Ge₂Sb₂Te₅

Abstract

We propose and demonstrate a cascaded dual-channel fiber surface plasmon resonance (SPR) sensor based on a phase change material, Ge <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Sb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Te <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> (GST). This material may modulate the sensing bands of SPR to the infrared bands. We configure channel I with a 50 nm Au film and configure channel II with a 50 nm Au film and a 30 nm GST film. The experimental results show that the sensing bands of channel I are 596 nm - 793 nm, and the refractive index (RI) sensitivity is 2781 nm/RIU. The sensing bands of channel II are 1045 nm - 1421 nm, and the RI sensitivity reaches 5226 nm/RIU. The RI measuring range is 1.333 - 1.403. The sensing bands of the two channels are completely separated. We coat polydimethylsiloxane (PDMS) on the surface of Au-GST film. Since PDMS is a heat-sensitive material with a high thermo-optical coefficient (TOC), channel II responds to temperature. Therefore, the sensor can also be used to measure the TOC of unknown liquid samples. The temperature sensitivity reaches 5.88 nm/°C. The sensor has high sensitivity, high resolution, good stability, and strong toughness. These advantages meet the requirements of biochemistry for high-precision and harsh experimental environments. We believe that the sensor has bright application prospects.