High-Linearity Refractive Index Sensor Based on Analyte-Filled Defect Hollow Core Bragg Fiber

We propose a high-linearity refractive index (RI) sensor based on an analyte-filled defect hollow core Bragg fiber (DHCBF) for large dynamic ranges. A resonant wavelength induced by the transverse coupling between core modes and defect modes is used as the characteristic wavelength for realizing a high-linearity RI sensor. The numerical results show that the linear correlation between characteristic wavelength and analyte RI can be significantly improved by optimizing structural parameters of a defect layer, which would be beneficial to the enlargement of dynamic measurement range. Furthermore, we numerically demonstrated an RI sensor with the sensitivity of 2062 nm/RIU and the adjusted R-Square value of 0.99967 in the measurement range of 1.324-1.432, by using an analyte-filled DHCBF with a low RI-contrast cladding. Compared with that based on a standard HCBF, our proposed high-linearity RI sensor can achieve high sensitivity in a larger dynamic range.