Refractive index sensor of a photonic crystal fiber Sagnac interferometer based on variable polarization states

Micron-sized holes distributed in the cross section of photonic crystal fibers allow the integration of the microfluidic analyte and fiber which makes it possible for rapid and effective chemical analysis. The innovation of this paper is that the polarization states of the fiber modes vary with the wavelength. The polarization directions of the two polarized modes are nearly 45 degrees with the horizontal direction at a certain wavelength, then the resonance wavelength will appear by a fiber Sagnac interferometer. The average sensitivity is up to −19040 nm/RIU as the refractive index of the microfluidic analyte varies from 1.33 to 1.37.