Regensburg 2010 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 2: SC: Applications and Measuring Devices
TT 2.8: Talk
Monday, March 22, 2010, 12:15–12:30, H19
Coherent broadband continuous-wave THz spectrometry: A powerful tool for low-energy solid-state spectroscopy at low temperature and high magnetic field — •Komalavalli Thirunavukkuarasu1, Holger Schmitz1, Axel Roggenbuck2, Andreas Janssen1, Anselm Deninger2, Iván Cámara Mayorga3, Joachim Hemberger1, Rolf Güsten3, and Markus Grüninger1 — 1II. Physikalisches Institut, Universität zu Köln, D-50937 Köln, Germany — 2TOPTICA Photonics AG, Lochhamer Schlag 19, D-82166 Gräfelfing, Germany — 3Max-Planck Institute for Radio Astronomy, Auf dem Hügel 69, D-53121 Bonn, Germany
We present the development of a continuous-wave THz spectrometer and its application at low temperatures and high magnetic fields. The spectrometer employs photomixing of two NIR-DFB diode lasers for generation and phase sensitive detection of THz radiation of frequency from 60 GHz to 1.8 THz. A phase modulation technique and photocurrent correction are used to accurately determine amplitude and phase at a given frequency, and to correct for instabilities, respectively. The complex optical functions can be evaluated from the full THz phase information, and a very high spectral resolution in the MHz range can be achieved. Furthermore, this compact spectrometer can be integrated within a magnetic cryostat eliminating the need for optical windows. In this way, the investigations at high magnetic fields up to 16 T and low temperatures up to 2 K can be achieved without loss of intensity. Thus, a new door is opened for exploring low-energy electronic excitations of novel materials, lying in the sub-phonon energy regime.