Determination of the dielectric function of strongly anisotropic crystals in reflection

We suggest that the optical dielectric function of absorbing and strongly anisotropic crystals can be determined by combining ellipsometry and polarimetry in reflection experiments. The advantage of ellipsometry is its sensitivity to average optical properties, whereas polarimetry detects the optical anisotropy most sensitively. The concept is systematically tested with different dielectric materials, and it is applied to a detwinned YBa2Cu3O7-x single crystal at discrete photon energies between 1.2 and 2.7 eV. The results show evidence for structural variations of the Cu-O chains. A polarimetric measurement on a (110) face of CuO demonstrates the ease of detecting the absence of two-dimensional P symmetry in the reflecting surface. (C) 1996 Optical Society of America