Ultra-sensitive polymeric waveguide temperature sensor based on asymmetric Mach–Zehnder interferometer

We proposed and designed an ultra-sensitive polymeric waveguide temperature sensor based on an asymmetric Mach–Zehnder interferometer that has different widths in the two interferometer arms. A polymer with a larger thermo-optic coefficient (TOC) was employed to enhance the sensitivity of the waveguide temperature sensor. The influence of the width difference between the two arms and the cladding materials with different TOCs on the sensitivity of the sensor was studied and experimentally demonstrated. The devices were fabricated by using the standard photolithography and simple all-wet etching process. When the cladding material Norland optical adhesive 73 (NOA 73) and the width difference of 6.5 μm were selected, the sensitivity of the waveguide temperature sensor was measured to be 30.8 nm/°C. Moreover, the minimum temperature resolution was about 0.97×10−3°C. The proposed sensor has the distinct advantages of high sensitivity, high resolution, easy fabrication, low cost, and biological compatibility, which make it have potential applications in temperature detection of organisms, molecular analysis, and biotechnology.