Measurement of phase refractive index directly from phase distributions detected with a spectrally resolved interferometer

A phase refractive index is measured directly from an unwrapped spectral phase distribution whose 2 π ambiguity is determined by fitting the spectral phase distribution with functions based on Cauchy’s equation. The phase refractive index of a quartz glass with 20 µm thickness is measured exactly from three spectral phase distributions detected in two different configurations of a spectrally resolved interferometer. Since there is a high possibility that the 2 π ambiguity cannot be correctly determined when there is a large difference between a function of the real refractive index and Cauchy’s equation, characteristics of the fitting are examined.