Spectral And Angular Responses Of High Sensitivity Refractive Index Sensors Based On Titanium Nitride

Refractive index sensors of high sensitivity were built by depositing thin films of titanium nitride and plane waveguides made of Nb2O5 and SiO2 on the planar face of D-shaped prisms, by dc and rf magnetron sputtering. Devices with structures Glass/TiN, Sapphire/TiN and Sapphire/TiN/SiO2/Nb2O5 were studied. Measurements of reflectance as a function of the angle of incidence were made in the Kretschmann configuration. For devices Glass/TiN and Sapphire/TiN, typical broad absorption band was observed. For devices with structure Sapphire/TiN/SiO2/Nb2O5, we observed a sharp reflectance peak, at a very well defined value of the angle of incidence within the broad absorption band, attributed to the phenomena of Plasmon Induced Transparency (PIT) and Fano resonance. Then, in the range of incidence angle values for which PIT and Fano resonance were observed, we studied the spectral response in the range of wavelength between 400 and 800 nm. Results show that high sensitivity sensors may also be used as tunable-by-incidence-angle optical filters. All data, reflectance vs angle of incidence and reflectance vs wavelength, were fitted by using a calculation program based on the solutions to Maxwell equations and boundary conditions.