THz-spectroscopy with YBa2Cu3O7-Josephson junctions on LaAlO 3-bicrystals

For the detection and spectral characterization of transition radiation in the operation of the linear accelerator at the TESLA test facility (TTF) we employ Hilbert-transform spectroscopy with Josephson junctions from high-temperature superconductors (HTS). The Josephson junctions with integrated wideband antennas from HTS are prepared on symmetric 24° LaAlO₃ bicrystal substrates. The set-up is optimized for low insertion loss over a wide frequency range from 50 GHz to about 2 THz. The HF-characterization is made by microwave Hilbert-transform spectroscopy with a far-infrared laser at 762 GHz and 1.2 THz. The spectral reconstruction of pulsed radiation in dependence of measuring time, signal-to-noise ratio, system noise, junction output voltage and repetition rate of pulsed radiation is deduced from simulation measurements of the Josephson junction response. For the spectral measurement of a single pulse we recommend quasi-optical time delay structures and high repetition rates of generated pulses