c-axis infrared response of Tl2Ba2Ca2Cu3O10 studied by oblique-incidence polarized-reflectivity measurements

We show that from measurements of the reflectivity of a uniaxial medium taken at a finite incidence angle with s- and p-polarized light it is possible to determine the dielectric function both parallel and perpendicular to the optical axis. When applied to layered compounds with its surface parallel to the layers, this technique allows for an accurate determination of the loss function perpendicular to the layers. This is demonstrated for the example of c-axis-oriented thin films of the high-T(c) superconductor Tl2Ba2Ca2Cu3O10, on which we carried out polarized reflectivity measurements at 45-degrees incidence angle above and below T(c).