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Terahertz time-domain magneto-spectroscopy

6/03/2012 Jean Léotin, LNCMI-Toulouse

A revival of THz magneto-spectroscopy is nowadays taking place with implementation of simple and reliable time-domain spectrometers based on novel femtosecond lasers. One basic advantage of time-domain spectroscopy (TDS) is simultaneous measurement of amplitude and phase spectra of the THz electric field. Moreover, the measurement is ultrafast, coherent, covers a wide spectral range, typically from 0.1 to 5THz, and can ultimately display signal to noise ratio up to 6 orders of magnitude in power. As a result, combining TDS techniques with high magnetic fields gives a powerful probe to investigate and even control coherently the dynamics of numbers of charge and spin excitations in condensed matter systems, since these excitations are largely distributed in the THz range (1 THz = 4.1 meV). In this talk, I’ll first review TDS development and then report two implementations of time-domain cyclotron resonance spectroscopy using pulsed magnetic fields. The first experiment relies on a fast mechanical delay line that enables to record over 100 spectra during a long magnet shot (500ms) [1]. The second uses a repetitive short pulse magnet (5 ms at a repetition rate of 5s) and proceeds via step-can recording of the time-domain signal [2].
 [1] High-speed terahertz time-domain spectroscopy of cyclotron resonance in pulsed magnetic fields ; D. Molter, F. Ellrich, T. Weinland, S. George, M. Goiran, F. Keilmann, R. Beigang, and J. Léotin ; OPTICS EXPRESS 26163, December 2010 / Vol. 18, No 25

[2] Step-Scan Terahertz Time-Domain Magneto-Spectroscopy, D. Molter, G. Torosyan, G. Ballon, L. Drigo, R. Beigang, and J. Léotin ; OPTICS EXPRESS (accepted , Feb. 2012)