Abstract
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 (TiO2) 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 μm, 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.
Highlights
Many fiber-optic sensors for refractive index (RI) sensing have been developed due to some advantages such as small size, high sensitivity, light weight, and immunity to external electromagnetic interference
We proposed a D-shaped optical fiber coated with a high refractive index titanium dioxide (TiO2) nanofilm to enhance the sensitivity and to extend the detection range of the sensor
The wavelength interrogation method along with D-lossy mode resonance (LMR) type optical fiber sensors was considered in our analysis
Summary
Many fiber-optic sensors for refractive index (RI) sensing have been developed due to some advantages such as small size, high sensitivity, light weight, and immunity to external electromagnetic interference. Various fabrication methods for fiber-based RI sensors have been reported in the literature [1], including surface plasmon resonance (SPR) [2, 3], evanescent field [4], fiber gratings [5, 6], and optical fiber interferometry [7]. Optical fiber sensors based on evanescent wave generate a strong interaction between the guided wave and the surrounding materials. Most of the reported sensors showed a low-sensitivity or low-detection range. To overcome this problem, we proposed a D-shaped optical fiber coated with a high refractive index titanium dioxide (TiO2) nanofilm to enhance the sensitivity and to extend the detection range of the sensor
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