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Subject: search.filters.subject.530Institute: search.filters.UBSInstitut.Stuttgart Research Centre of Photonic Engineering (SCoPE)Institute: search.filters.UBSInstitut.Zentrum für integrierte Quantenwissenschaft und -technologie (IQST)Author: search.filters.author.Giessen, HaraldAuthor: search.filters.author.Meyer zu Heringdorf, Frank-Joachim

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Now showing 1 - 3 of 3
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    Momentum space separation of quantum path interferences between photons and surface plasmon polaritons in nonlinear photoemission microscopy
    (2024) Dreher, Pascal; Janoschka, David; Giessen, Harald; Schützhold, Ralf; Davis, Timothy J.; Horn-von Hoegen, Michael; Meyer zu Heringdorf, Frank-Joachim
    Quantum path interferences occur whenever multiple equivalent and coherent transitions result in a common final state. Such interferences strongly modify the probability of a particle to be found in that final state, a key concept of quantum coherent control. When multiple nonlinear and energy-degenerate transitions occur in a system, the multitude of possible quantum path interferences is hard to disentangle experimentally. Here, we analyze quantum path interferences during the nonlinear emission of electrons from hybrid plasmonic and photonic fields using time-resolved photoemission electron microscopy. We experimentally distinguish quantum path interferences by exploiting the momentum difference between photons and plasmons and through balancing the relative contributions of their respective fields. Our work provides a fundamental understanding of the nonlinear photon-plasmon-electron interaction. Distinguishing emission processes in momentum space, as introduced here, could allow nano-optical quantum-correlations to be studied without destroying the quantum path interferences.
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    Quantitative determination of the electric field strength in a plasmon focus from ponderomotive energy shifts
    (2022) Dreher, Pascal; Janoschka, David; Neuhaus, Alexander; Frank, Bettina; Giessen, Harald; Horn-von Hoegen, Michael; Meyer zu Heringdorf, Frank-Joachim
    Spectroscopic photoemission microscopy is used to detect and quantify a ponderomotive shift in the energy of electrons that are emitted from a surface plasmon polariton focus. The focus is formed on an atomically flat Au(111) surface by an Archimedean spiral and is spatiotemporally separated from the circularly polarized light pulse used to excite the spiral. A spectroscopic analysis of electrons emitted from the focus exhibits a peaked above-threshold electron emission spectrum. From the shift of the peaks as function of laser power the field strength of the surface plasmon polariton was quantitatively determined without free parameters. Estimations of the Keldysh parameter γ = 4.4 and the adiabaticity parameter δ = 4700 indicate that electron emission occurs in a regime of multiplasmon absorption and nonlocalized surface plasmon fields.
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    Focused surface plasmon polaritons coherently couple to electronic states in above-threshold electron emission
    (2023) Dreher, Pascal; Janoschka, David; Frank, Bettina; Giessen, Harald; Meyer zu Heringdorf, Frank-Joachim
    When an intense light field strongly interacts with the band structure of a solid, the formation of hybrid light-matter quantum states becomes possible. Examples of such Floquet-Bloch states have been reported, but engineering of the band structure using Floquet states can suffer from dissipation and decoherence. Sustaining the necessary quantum coherence of the light-matter interactions requires robust electronic states in combination with strong fields of suitable polarization and frequency. Here, we explore the quantum coherent coupling of nano-focused surface plasmon polaritons (SPP) to distinct electronic states in the band structure of a solid. We observe above-threshold electron emission from the Au(111) Shockley surface state by the absorption of up to seven SPP quanta. Using time-resolved photoelectron spectroscopy the coherence of the interaction of the SPPs with the surface state during electron emission is investigated and the process is shown to be similar to light-driven above threshold electron emission. Ultimately, our work could render SPP-based Floquet engineering in nano-optical systems feasible.