The interference method for simultaneous measurement of the absolute refractive index and the thickness of plane parallel samples is developed. This method enables us to test solid (including optical glasses, crystals, plastics, and other sheet materials), liquid, and gaseous media over a wide spectral range. The experimental model for the realization of this method, the laser interference refractometer and thick- nessmeter (IRT), is manufactured and investigated. The IRT accuracy of the refractive index measurement is not worse than that of the best modern goniometers and the accuracy of the thickness measurement corresponds to the interference accuracy.
Serguei A. Alexandrov,
Igor V. Chernyh,
"Interference method for determination of the refractive index and thickness," Optical Engineering 39(9), (1 September 2000). http://dx.doi.org/10.1117/1.1287583