Berlin 2005 – scientific programme

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HL: Halbleiterphysik

HL 17: Poster Ib

HL 17.33: Poster

Friday, March 4, 2005, 16:30–19:00, Poster TU F

Time-resolved THz-spectroscopy of Graphite — •Florian Schapper, Tobias Kampfrath, Luca Perfetti, Christian Frischkorn, and Martin Wolf — Fachbereich Physik der Freien Universität Berlin, Arnimallee 14, 14195 Berlin

We excite graphite with short laser pulses centered at 775 nm and subsequently probe its in-plane optical properties with mid-infrared pulses in a frequency range of about 8 to 28 THz. The field-resolved sampling of the probe pulses allows for the determination of the transient dielectric function of the sample. It contains a Drude-like response and a contribution induced by the blocking of direct optical transition. We are able to extract the temporal evolution of the electronic temperature, plasma frequency, and Drude current relaxation rate. Our results give evidence for the generation of hot optical phonons, which contribute strongly to a striking increase of the Drude relaxation rate by more than 100% during the first picosecond after excitation.

We present first results on shaping mid-infrared pulses by shaping the visible generation pulses.