High Sensitivity Refractive Index Sensor by D-Shaped Fibers and Titanium Dioxide Nanofilm

This paper presents a high sensitivity liquid refractive index (RI) sensor based on lossy mode resonance (LMR) effect. The D-shaped fibers coated with nanosized titanium dioxide (TiO 2 ) thin film as a sensing head were submerged into different refractive index solutions. The variations in the optical spectrum of the proposed RI sensor with different refractive index solutions were measured. The LMR resonance peaks were used to determine the wavelength shifts with different refractive index solutions. The results show that the optical spectrum peaks shifted towards the longer wavelength side with increasing the refractive index. For the proposed fiber sensing head with a polishing residual thickness of 72 μ m, the maximum shift of the absorption peak was 264 nm. The sensitivity of the proposed RI sensor was 4122 nm/RIU for the refractive index range from 1.333 to 1.398.