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TT: Fachverband Tiefe Temperaturen

TT 10: Measuring Devices, Cryotechnique: Poster Session

TT 10.2: Poster

Montag, 22. März 2010, 14:00–18:00, Poster A

Coherent broadband cw THz spectroscopy on solid-state samples: recent improvements — •H. Schmitz¹, A. Roggenbuck^1,2, K. Thirunavukkuarasu¹, A. Janssen¹, A. Deninger², I. Cámara Mayorga³, J. Hemberger¹, R. Güsten³, and M. Grüninger¹ — ¹II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 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 aim at the precise determination of the complex dielectric function ε(ω) of solid state samples in the THz range. Our spectrometer employs photomixing of two NIR lasers. The photomixer efficiently converts the laser beat into THz radiation from 60 GHz to 1.8 THz. The signal is coherently detected using a second photomixer which preserves the THz phase information. In order to determine ε(ω), we either sweep the frequency in small steps (∼ 30 MHz) or we modulate the phase of the laser beat. This can be achieved using a fiber stretcher which modulates faster than a mechanical delay stage. In addition, we implement a photocurrent correction to account for drifts in the THz intensity using the dc photocurrents measured at the photomixers. We demonstrate the excellent performance of the spectrometer for different solid state samples.