Augsburg 2006 – wissenschaftliches Programm

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K: Kurzzeitphysik

K 1: Neue Verfahren I

K 1.1: Hauptvortrag

Montag, 27. März 2006, 15:00–15:30, 1003

Ultrafast pump-probe and THz spectroscopy without mechanical delay line — •Albrecht Bartels — Universität Konstanz and Center for Applied Photonics, Universitätsstrasse 10, 78457 Konstanz — Gigaoptics GmbH, Blarerstraße 56, 78462 Konstanz

We present an ultrafast spectrometer that is capable of acquiring optical pump-probe and THz transients over 1 ns time-delay with ≈200 fs time-resolution. Temporal scanning is performed without mechanical delay line at a rate of 10 kHz, thus data acquisition times are reduced by approximately two orders of magnitude compared to conventional techniques employing mirrors on stepper motors or vibrating membranes. A spectral resolution of ≈1 GHz is demonstrated for coherent phonon spectroscopy on a GaAs/AlAs superlattice. Time-domain THz spectroscopy is performed at up to 3 THz and high-resolution water vapor absorption spectra with a 30 dB dynamic range are obtained within only 25 s of total acquisition time. The spectrometer is based on high-speed asynchronous optical sampling and employs two Ti:sapphire femtosecond lasers whose 1 GHz repetition rates are linked at a fixed difference. Consequently, their time-delay is automatically ramped between zero and 1 ns and the lasers are employed as pump- and probe-laser, respectively. In addition to rapid data acquisition and real-time signal optimization, significant advantages of the method are the absence of pointing or spot size variations at the sample position as time-delay is scanned. Furthermore, two-color spectroscopy is straightforward.