DETERMINATION OF THE DIELECTRIC FUNCTION OF STRONGLY ANISOTROPIC CRYSTALS IN REFLECTION

We suggest that the optical dielectric function of absorbing and stron gly anisotropic crystals can be determined by combining ellipsometry a nd polarimetry in reflection experiments. The advantage of ellipsometr y is its sensitivity to average optical properties, whereas polarimetr y detects the optical anisotropy most sensitively. The concept is syst ematically tested with different dielectric materials, and it is appli ed to a detwinned YBa2Cu3O7-x single crystal at discrete photon energi es between 1.2 and 2.7 eV. The results show evidence for structural va riations of the Cu-O chains. A polarimetric measurement on a (110) fac e of CuO demonstrates the ease of detecting the absence of two-dimensi onal P symmetry in the reflecting surface. (C) 1996 Optical Society of America