A METHOD FOR THE OPTICAL CHARACTERIZATION OF THIN UNIAXIAL SAMPLES

An optical characterization procedure for small fragments of uniaxial materials is described involving the simple use of crossed polarizers with one polished face of the material. The reflectance at a fluid-uni axial slab boundary beyond, but near, the critical angle of incident l ight is examined for linear incidence polarization using an orthogonal output polarizer. It is found that, as the crossed incident and outpu t polarizers are rotated together, there are, for a given angle of inc idence, particular polarization angles for which the reflectivity is a minimum. These angles give information on the optical tenser of the c rystal under study. Further the intensity of the reflected light, for incidence angles beyond critical with the input and output polarizers crossed, has as a function of the incident polarization angle an oscil latory form which, when fitted to theory, can also yield the full unia xial tenser of the material under study. This is confirmed experimenta lly for a thin single crystal of calcite with one polished face.