Hyperspectral measurement of dispersion in aqueous solution and its effect on ultra-sensitive interferometer.

Abstract

Since the reported Sellmeier equation of water is fitted with sparse sampling points in the near-infrared region, the simulated refractive index sensitivity of dispersion enhanced interferometers deviates from the true value. Here, we measure the refractive index of aqueous sample based on hyperspectra, and research the effect of dispersion on ultra-sensitive interferometer. A piece of quartz plate is used to generate hyperspectra in the near-infrared region by building a wavefront splitting fiber Mach-Zehnder interferometer (WFSF-MZIs). The refractive index of saline water is tested after measuring the thickness of the quartz plate. By taking the wavelength of 1450 nm as break-point, the empirical dispersion equations of saline water are piecewise fitted. When the normal and abnormal dispersion are taken into account, the theoretical sensitivity of phase compensated WFSF-MZI is in good agreement with the experimental results. Our methodology provides a good reference in designing dispersion sensitized optical refractive index sensor for detecting aqueous samples.