SAMOP 2023 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 6: Poster I

MO 6.11: Poster

Dienstag, 7. März 2023, 16:30–19:00, Empore Lichthof

Ultrafast coherent control of single molecules via two-photon excitation at room temperature — •Xinpeng Xu¹, Ullrich Scherf², and Richard Hildner¹ — ¹Zernike Institute for Advanced Materials, University of Groningen, The Netherlands — ²Institut für Polymertechnologie, Universität Wuppertal, Germany

Quantum coherent control has been a powerful technique to understand and manipulate ultrafast photoinduced processes occurring at the inter-/intra-molecular level for more than twenty years. In a coherent control experiment, one can exploit quantum interference between competing pathways of multiphoton transitions toward the desired outcome by tailoring the spectral phase, amplitude, or polarization of the electromagnetic field of the exciting laser. For larger functional molecules in condensed phase, the influence of the (often disordered) surrounding environment varies between molecules. Hence, ensemble measurements do typically not allow to exert full control over competing pathways. Here, we demonstrate that the two-photon transition of single molecules can be controlled by a sequence of shaped pulses at room temperature. Varying the spectral phase of the pulses, we observe phase-dependent photoluminescence signals corresponding to the two-photon excitation probability. We assign this phase dependence to the combination of quantum photon interference and coherence between the incident laser spectrum and the single molecule absorption spectrum. Notably, cancellation of the transition probability by so-called *dark pulses* is observed in some molecules, which shows the ability to fully coherent control of single molecules in condensed phase.