Optimization of waveguide parameters for minimization of the sensitivity temperature dependence for the SiO2:TiO2 planar waveguide optical sensor

This study focuses on investigating how changes in temperature affect the sensitivities of an optical sensor that uses a SiO2:TiO2 planar waveguide, with particular emphasis on the fundamental modes sensitivities. The results showed that, by accurately determining the appropriate core thickness for each set of physical parameters of the waveguide, we not only increased the sensitivity, but also extended its stabilization range with respect to the temperature. The best results, in terms of values and stabilities of the sensitivities were obtained for a high refractive index of the core and selecting a measurand refractive index closest to that of substrate. As regards the geometrical parameters, the most favorable results can be attained for the core thicknesses located between the thickness corresponding to the maximum sensitivity at room temperature and the cut-off thickness of the TM0 mode, the sensitivity remain relatively stable at the vicinity of 0.41. However, for the monomode structure, the best results can be achieved for the core thicknesses situated between the thickness corresponding to the maximum sensitivity at room temperature and twice the cut-off thickness of the TE0 single mode, the average sensitivity is relatively constant at around 0.35.