Abstract

A phase refractive index is measured directly from an unwrapped spectral phase distribution whose ${2}\pi$ 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 ${2}\pi$ 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.

© 2021 Optical Society of America

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