Investigation of High Temperature Superconductors with Terahertz Bandwidth Electrical Pulses.

We summarize recent attempts to propagate ultrashort electrical pulses containing frequency components up to 1-THz on transmission lines made from thin films of the high temperature superconductor YBa sub 2 Cu sub 3 O sub 7 delta. Optoelectronic generation of extremely short electrical transients and jitter-free electrooptic detection of the pulse shape and amplitude as they propagate along the superconducting line enable us to investigate the high-frequency properties of the high-T sub c material with high accuracy because of the long interaction lengths that are possible on transmission lines. We discuss the influence of epitaxy, surface roughness and magnetic field on the pulse propagation. Important parameters like the magnetic penetration depth lambda (T) and the superconducting energy gap DELTA are directly determined from the experimental data. Finally, we compare our results with weak coupling BCS theory.