Dresden 2009 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

DF 11: Photonic Dielectrics II

DF 11.5: Vortrag

Mittwoch, 25. März 2009, 16:10–16:30, WIL A317

Photo-induced light scattering of femtosecond laser pulses in iron-doped lithium niobate crystals* — •Johanna Bückers, Dominik Maxein, Daniel Haertle, and Karsten Buse — Institute of Physics, University of Bonn, Wegelerstr. 8, 53115 Bonn, Germany

Lithium niobate is an advantageous material for photonics, e.g., holographic spectral filtering, optical image processing, and holographic diffraction can be realized. However, since lithium niobate crystals are photorefractive, illumination of the crystals is accompanied with undesirable effects like the “optical damage” and “photo-induced light scattering”. Photo-induced light scattering leads to a loss of the transmitted light because of the self-amplification of weak scattered coherent light waves. Consequently, it causes a distortion of the beam shape of the incoming light wave and, thus, hinders photonic applications.

Our investigations show that for femtosecond laser pulses the light-induced scattering is reduced in LiNbO₃:Fe in comparison to illumination with cw laser light at 532 nm. Moreover, it is completely absent for femtosecond pulses in samples with sufficiently small Fe²⁺ content, in contrast to the scattering of cw light. Further differences are reflected in a slower buildup time, a narrower angular distribution of the scattered light, and a weaker Bragg selectivity for pulsed illumination. These characteristics can be attributed to the shorter coherence length of femtosecond pulses.

*Financial support from the Deutsche Forschungsgemeinschaft (FOR 557) and the Deutsche Telekom AG is gratefully acknowledged.