Berlin 2012 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 33: Superconductivity, Measuring Devices, Matter at Low Temperature: Poster Session
TT 33.72: Poster
Mittwoch, 28. März 2012, 15:00–19:00, Poster B
Coherent broadband THz spectrometer using photomixers for accurate determination of complex dielectric function — •Malte Langenbach1, Komalavalli Thirunavukkuarasu1, Holger Schmitz1, Ernesto Vidal1, Jennifer Marx1, Iván Cámara Mayorga2, Rolf Güsten2, Axel Roggenbuck3, Anselm Deninger3, Joachim Hemberger1, and Markus Grüninger1 — 1II. Physikalisches Institut, Universität zu Köln, Köln, Germany; — 2Max-Planck-Institut für Radioastronomie, Bonn, Germany; — 3Toptica Photonics AG, Gräfelfing, Germany
We report on a novel cw THz spectrometer for measurements in high magnetic fields and at low temperatures. The spectrometer employs photomixing of two NIR lasers for generation and phase-sensitive detection of THz radiation from 60 GHz to 1.8 THz. A fast phase-modulation technique using two fiber stretchers is used to determine the amplitude and the phase at a given frequency with excellent reliability. The phase accuracy is increased with further implementation of a third laser which enables correction of phase drifts mainly caused by thermal drifts. Thus, the complex dielectric function can be determined very accurately with a very high resolution in the MHz range. This compact spectrometer in combination with the magneto-cryostat allows for investigations in magnetic fields up to 8 T and temperatures down to 3 K with excellent reliability. Various aspects of the above-mentioned developments will be outlined.