Regensburg 2010 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 2: SC: Applications and Measuring Devices

TT 2.1: Talk

Monday, March 22, 2010, 10:15–10:30, H19

Josephson-Cantilever with integrated THz antenna — •Christian Brendel, Heiko Neeland, Tobias Vosskoetter, 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 microwave power distributions at the open end of multimode circular waveguides and in the free space in the THz range. 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. As scanning sensor we employ a Josephson junction from the high-temperature superconductor YBa₂Cu₃O₇ on a vibrating cantilever prepared from a LaAlO₃-bicrystal. The setup is mounted inside a vacuum chamber on x-, y- and z-tables with submicrometer resolution and is cooled to a temperature of about 50 K by a cryocooler. We realized a quasi-optic THz-lens system and determined the beam parameters at the Josephson-cantilever position. The small change of the differential resistance in the Shapiro step is proportional to the microwave power. To improve the signal to noise ratio in the measured curent voltage curve we developed new Josephson cantilever designs with different THz antenna strutures.

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