INTERFEROMETRIC DETERMINATION OF THE BIREFRINGENCE DISPERSION OF ANISOTROPIC MATERIALS

A channelled spectrum resulting from two-beam interference fringes is formed by illuminating an anisotropic material, placed between two cro ssed polarizers in front of a spectrograph, with a parallel beam of wh ite light. The resulting interferogram is analyzed by a simple approac h to deduce the birefringence and its dispersion across the visible sp ectrum. A Cauchy and a fourth-order polynomial dispersion formula are used to fit the experimental data for a mica sheet and a transparency film. The method is simple, direct and accurate for deducing the biref ringence of anisotropic materials and its dispersion. (C) 1997 Elsevie r Science B.V.