High sensitive temperature sensor based on a polymer waveguide integrated in an optical fibre micro-cavity

A Mach-Zehnder interferometer (MZI) based on a polymer waveguide integrated in an optical fibre micro-cavity was proposed. The micro-cavity with two symmetric openings was fabricated in single mode fibre by using femtosecond laser micromachining and fibre splicing. Then, the polymer waveguide with a length of 70 μm was integrated into the micro-cavity by using a two-photon polymerization fabrication method. The MZI exhibited a perfect interference spectrum with a fringe visibility of almost 25 dB. Owing to the high thermo-optical coefficient of the polymer material, the temperature sensitivity of the proposed MZI reached 447 pm/°C. Meanwhile, it can be used as a reliable temperature sensor as its perfect linearity (99.7%) and repeatability.