Thermo-Optic Property Measurement Using Surface Plasmon Resonance-Based Fiber Optic Sensor
Yuzhi Chen, Lin Fang, Duo Yi, Xuejin Li, Xueming Hong
Abstract
The temperature disturbances greatly influence the performances of microfluidic chips during the working process. It is therefore important to evaluate the thermo-optic properties of microfluidic materials. Here, we measure the thermo-optic property by employing a fiber optic surface plasmon resonance (SPR) sensor combined with a thermocouple. This setup can be applied for embedding in microfluidic materials or directly detecting fluidic samples. Three fiber optic SPR sensors were fabricated with a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$400~\mu m$ </tex-math></inline-formula> -bare-core, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$600~\mu m$ </tex-math></inline-formula> -bare-core and mismatched-core structures. The thermo-optic responses of the three sensors were compared to determine the optimum sensor structure. The thermo-optic property of polydimethylsiloxane was then investigated over the full temperature detection range of 25–200 °C. The thermo-optic coefficient of polydimethylsiloxane was determine to be <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$- 4.19\times 10^{-4}$ </tex-math></inline-formula> RIU/°C, which agrees well with previous reports. The thermo-optic properties of ethanol and brine were also evaluated to confirm the universality of the proposed measurement method. To our knowledge, this is the first reported detection of thermo-optic properties using a fiber optic SPR sensor.