Freiburg 2024 – scientific programme
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MO: Fachverband Molekülphysik
MO 27: Ultrafast Dynamics III and High-harmonic Generation (joint session MO/A)
MO 27.7: Talk
Friday, March 15, 2024, 16:00–16:15, HS 3044
Observation of HHG from organic molecular crystals — •Falk-Erik Wiechmann1, Samuel Schöpa1, Alexander Villinger2, Dieter Bauer1, and Franziska Fennel1 — 1Institute of Physics, Rostock, Germany — 2Institute of Chemistry, Rostock, Germany
This project aims at a detailed understanding of the harmonic generation process in large organic molecules in the crystalline phase. Unlike previous studies, which were limited to small molecules in the gas phase, we introduce organic molecular crystals as a novel target for HH spectroscopy, taking advantage of the inherent molecular alignment. Unlike in gas phase experiments, neighboring molecules in organic crystals experience a weak but finite coupling, leading to 'solid like' features, e.g. a delocalization of the electronic states over several unit cells. With a fundamental 4000 nm mid-IR beam reaching 6 TW/cm2 we demonstrate that HHG up to the order of 17 is possible without imposing physical damage. When the fundamental driving polarization is rotated, maxima of harmonic emission occur at polarization directions parallel to connecting axes between neighboring molecules, reflecting the crystal structure. Despite the linearly polarized driving field, the emitted harmonics exhibit elliptical polarization with a main axis different from the fundamental polarization direction.
Keywords: High harmonic generation; Organic molecular crystals; Pentacene; Molecular alignment; Elliptical polarization