Optical anisotropy of YBa2Cu3O/sub 7-//sub x/

The optical anisotropy of YBa2Cu3O/sub 7-//sub x/ in the 0.08--5.6 eV region is investigated by polarized reflectance measurements on single crystals, and by transmittance, reflectance, and ellipsometric measurements on oriented thin films. In the visible--near-uv spectral region the anisotropy is relatively mild, but a huge anisotropy is observed in the infrared. Here, the reflectance increases with decreasing frequency for both polraizations, consistent with metallic conductance both parallel and perpendicular to the ab plane. The c-axis plasma frequency is strikingly low, but there is strong damping which could originate from a continuum of low-energy interband transitions