Hamburg 2001 – scientific programme

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TT: Tiefe Temperaturen

TT 28: HF Anwendungen

TT 28.3: Invited Talk

Friday, March 30, 2001, 10:45–11:15, J

Terahertz Hilbert spectroscopy by high-Tc Josephson junctions — •Y. Y. Divin¹, V. V. Shirotov¹, U. Poppe¹, P. M. Shadrin¹, K. Urban¹, O. Y. Volkov², and V. V. Pavlovskii² — ¹IFF-IMF, Forschungszentrum Juelich GmbH, 52425 Juelich — ²Institute of Radioengineering and Electronics RAS, 103907 Moscow

The operation of Hilbert spectroscopy is based on the frequency-selective detection of weak electromagnetic radiation by Josephson junctions described by the resistively-shunted-junction (RSJ) model. The YBa2Cu3O7-x high-Tc grain-boundary Josephson junctions fabricated on twin-free bicrystal NdGaO3 substrates were found to be more close to the RSJ model in comparison with different types of junctions. General-purpose Hilbert spectrometers with high-Tc grain-boundary Josephson junctions integrated into a liquid-helium dewar and a Stirling cryocooler were developed. The spectral bandwidth of Hilbert spectroscopy for any junction temperature between 30 and 85 K was shown to be of one frequency decade. The middle frequency of this bandwidth scaled with the characteristic frequency fc = (2e/h)IcRn of the Josephson junction and a total bandwidth of almost two orders, from 50 GHz to 4 THz, was covered by one Josephson junction at two temperatures. The spectral resolving power of Hilbert spectroscopy was found to be of 10-3 in the terahertz range. The dynamic range of intensities of electromagnetic radiation, which can be measured by Hilbert spectroscopy, was found to be close to five orders. With a help of Hilbert spectroscopy we measured the following emission spectra: Lorentz spectra of Josephson oscillations, spectra of high-harmonic content in the commercial millimeter-wave oscillators, spectra of radiation from optically-pumped far-infrared lasers and spectra of coherent transition radiation from relativistic electron bunches at the TESLA Test facility at DESY (Hamburg).