Dresden 2006 – wissenschaftliches Programm
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DF: Dielektrische Festkörper
DF 11: Electric, Electromechanical and Optical Properties II
DF 11.5: Vortrag
Freitag, 31. März 2006, 12:30–12:50, M{\"U}L Elch
Holographic Investigation of Lithium Niobate Crystals with Femtosecond Laser Pulses* — •Peter Reckenthäler1, Dominik Maxein1, Oliver Beyer1, Boris Sturman2, and Karsten Buse1 — 1Physikalisches Institut, Universität Bonn, Wegelerstr. 8, 53115 Bonn — 2Institute of Automation and Electrometry, Novosibirsk, Russia
Lithium niobate is an important material for nonlinear and photorefractive applications. For short light pulses high intensities occur, and transient nonlinearities like the Kerr-effect and free charge-carriers, become increasingly important. These effects can be serious obstacles for applications. A profound understanding of the processes on the femtosecond-timescale is therefore indispensable. Holography with femtosecond laser pulses allows to investigate charge excitation and transport processes as well as other nonlinear effects with very high temporal resolution. Volume gratings are generated with two interfering pump pulses (λp = 388 nm, tp ≃ 200 fs) in lithium niobate crystals, and time-resolved read out is performed using a probe pulse (λr = 776 nm, tr ≃ 200 fs). The diffraction efficiency shows mainly two features: A sharp peak with a width of the order of the pump-probe-crosscorrelation, and a plateau which is constant on the picosecond timescale. Matching the Bragg condition for the 2K contribution to the grating allows to separate different transient effects. With further experiments, it is possible to extract information about the build up of photorefractive gratings and to learn about the dynamics of charge separation on the femtosecond time scale.
* Financial support by the DFG (award BU 913 / 13) and the Deutsche Telekom AG is gratefully acknowledged.