Anisotropy in the transparency of HTS films at millimeter and submillimeter microwave radiation

The propagation of microwave radiation through YBa2Cu3O7-delta and Tl2Ba2Cu 1O6 films deposited on Al2O3, MgO, LaAlO3 and LaSrAlTaO single crystal subs trates, as well as through the bare substrates, has been studied in the 60- 600 GHz frequency range. The angular dependence of the transmitted radiatio n was found to have a rather complicated structure. The dependence is affec ted by anisotropy of the substrate doe to birefringence, resonance in subst rate modes, non-homogeneity and the granular structure of the HTS film. To reduce reflections from the surface of the substrate, quarter-wave matching Layers were used at selected frequencies. After correction for stray effec ts, the common feature is the presence of four maxima with a period of pi / 2 with four minima in between that can be due to the energy gap anisotropy in d-wave superconductors.