Dresden 2011 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 60: SC \& MLT: Cryodetectors

TT 60.7: Talk

Friday, March 18, 2011, 12:30–12:45, HSZ 301

3D power distribution scan of Gaussian beams and THz-antennas — •Christian Brendel, Alexander Guillaume, Jan M. Scholtyssek, and Meinhard Schilling — Institut für Elektrische Messtechnik und Grundlagen der Elektrotechnik, Technische Universität Braunschweig, Hans-Sommer-Str. 66, D-38106 Braunschweig, Germany

We imaged the three dimensional power distribution of far infrared Gaussian beams in the free space. Close to the beam waist we irradiated different THz antennas from below and scanned the radiation pattern in the 3D half space above the antennas. As scanning sensor we employ a Josephson-junction from the high-temperature superconductor YBa₂Cu₃O₇ on cantilever prepared from a LaAlO₃-bicrystal. The antenna on the Josephson-junction has to be smaller than the wavelength to achieve high spatial resolution but large enough to be able to detect sufficient power. Also the characteristic frequency, antenna impedance, bandwidth up to 1 THz and connection filters have to be optimized for a LaAlO₃-bicrystal substrate. The setup is mounted inside a vacuum chamber on x-, y- and z-tables with 15 mm scan length and is cooled down to a temperature of 38 K by a cryocooler. The measurement setup consists of a grating-tuned CO₂ laser (emission 9 - 11 µm) to pump a FIR laser with an output frequency range from 584 GHz up to 4.2 THz. We realized a quasi-optic THz-lens system to transfer the far infrared beam into the vacuum chamber.

We wish to acknowledge the financial support of C. Brendel by the Braunschweig International Graduate School of Metrology.