Dresden 2009 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

DF 11: Photonic Dielectrics II

DF 11.7: Vortrag

Mittwoch, 25. März 2009, 16:50–17:10, WIL A317

Determination of the light-induced absorption by transient grating spectroscopy — •Hauke Brüning, Bettina Schoke, and Mirco Imlau — Department of Physics, University of Osnabrück, Germany

Transient absorption spectroscopy is a well-known pump-probe technique for the study of optically-induced photochromic properties showing decay times in the ms and µs range. The spectral and temporal behavior of the light-induced absorption is determined from the transmission of white light or probe laser beams. Therefore, single intense laser pulses with a spatially homogeneous intensity distribution have to be applied for the pump process. In contrast, transient grating spectroscopy accounts for light diffraction from an optically-induced absorption grating recorded with spatially modulated pump light using a two-beam interferometer. For grating analysis, the probe-light diffraction efficiency is determined as a function of time and wavelength. Here we demonstrate the possibility to determine the light-induced absorption from transient grating spectroscopy in lithium niobate crystals as an example. Experimental results are presented for the particular case of the presence of mixed photochromic and photorefractive gratings, i.e. light-induced refractive-index changes contribute to the light diffraction as well. Theoretical considerations based on wave-mixing theory allowing for a comprehensive grating analysis are presented. Advantages of the procedure are discussed by comparison with results determined from transient absorption spectroscopy. *Financial support by the DFG (Projects IM37/5-1 and GRK 695).