Wideband Phase Refractive Indices and Group Index Measurement of Liquid Samples with low Coherent Fabry-Perot Interferometry

We present a simple method allowing simultaneous measurement of group and phase refractive indices of liquid samples by using low coherence Fabry-Perot (FP) interferometry and Fourier transform (FT) analysis. The liquid sample was placed in a very thin cuvettes and located within a fiber-type FP interferometer with a broad-band light source of 1.5 mu m wavelength region. The interference spectrum of the FP interferometer including the liquid sample was measured with an optical spectrum analyzer (OSA), and Fourier transform analysis on the spectrum was performed to determine the sample's refractive index profile over a broad spectral range. Our measurement method was proved by measuring the refractive index profile of a pure water. The accuracy of this method was within third decimal point for both the group refractive index and the phase refractive indices.