Optical properties of thin TiO2 film deposited on the fiber optic sensor head

The presented study was focused on investigation of the titanium dioxide (TiO2) thin film optical properties. The intention of this investigation was using TiO2 film in the construction of the optical fiber sensor head. In the demonstrated construction TiO2 thin layer was deposited on the tip of a commonly used telecommunication single mode optical fiber (SMF-28) by means of the Atomic Layer Deposition (ALD). Thickness of the fabricated film was 80 nm. The characterization of the optical properties focuses on the most significant factors for the application in the interferometric sensing devices, namely - spectral reflectance function and its thermal dependence. The measurements were performed using two broadband sources (SuperLuminescent Diodes (SLD)) with central wavelengths of 1300 nm and 1550 nm. The examination of the sensitivity of reflectance spectra to the thermal shift was conducted for temperatures in the range from 25 °C up to 150 °C. Obtained results have showed that the investigated layer exhibited high reflectance value. Moreover, while the variation in signal intensity induced by temperature change is noticeable, no significant spectral shift is observed in the reflection function. Therefore the examined structure presents interesting choice for use in the interferometric fiber optic sensors.