An interferometric technique based on Fourier fringe analysis for measuring the thermo-optic coefficients of transparent materials

We describe an interferometric technique based on temperature-dependent opt ical path length changes in a thin slab of transparent materials, suitable for measuring the thermal coefficient of refractive index. This technique a llows an accurate determination of the fringe shift corresponding to a chan ge in the sample temperature, by means of a two fringe pattern Fourier-tran sform-based processing algorithm for phase retrieval. The principle of meas urement of the method and its applications to the measurements of the therm o-optic coefficients of some commercial glasses are presented and discussed . (C) 1999 Published by Elsevier Science B.V. All rights reserved.