Response properties of waveguide-optic evanescent field refractive index sensors according to titanium dioxide thin film conditions

This study examined the response properties of a high-sensitivity waveguide-optic evanescent field refractive index sensor according to the conditions used to deposit the titanium dioxide (TiO₂) thin film. Rib-type silica waveguides were fabricated by plasma enhanced chemical vapor deposition, photolithography and plasma etching. The conditions, such as the thickness and length of a TiO₂ thin film on the silica waveguides, were controlled using a metal shadow-mask and the sputtering deposition parameters. The Polarimetrie interference patterns generated through an interaction between the waveguide and a glycerol solution showed a change in the degree of evanescent field strength according to the TiO₂ thin film deposition conditions. The results suggest that the sensitivity of the fabricated device can be improved by increasing the thickness (maximum-35 nm) and length of the TiO₂ thin film on the optical waveguide.