Ag micro-spheres doped silica fiber used as a miniature refractive index sensor

In this paper, a novel micro-fiber sensor was proposed and fabricated by the silica micro-fiber with the diameter of ∼2.3 μm and the Ag micro-spheres with the diameter of ∼1.3 μm. Its refractive index sensing properties we experimentally demonstrated using the NaCl solution with different concentrations. On its transmission spectra, both the wavelength and intensity of the characteristic peak depend on the refractive index difference of the analyte. The experimental results indicate that the wavelength and intensity sensitivities of the micro-fiber sensor are 19.2 nm/RIU and 40.5 μW/RIU, respectively, which are still far below than that of the simulation results, those are 520.1 nm/RIU and 333.5 μW/RIU, respectively. By optimizing the coupling method and preparation process, the performance of the micro-fiber sensor will be improved significant in the future work. This kind of miniature micro-fiber can be further explored to be the fluid and gas sensors with the high sensitivity.