1,091 research outputs found
Limitations and possibilities in painting: tracing the unrepresentable
No full textM.F.A.Includes bibliographical references (p. 13)by Viktor Lukas Witkowsk
Revealing the time-dependent polarization of ultrashort pulses with sub-cycle resolution
Full text linkWe report on the first experiments characterizing the complete time-dependent 2D vector potential of a few-cycle laser pulse. The instantaneous amplitude and orientation of the electric field is determined with sub-cycle resolution, directly giving access to the polarization state of the pulse at any instant in time. This is achieved by performing an attosecond streaking experiment using a reaction microscope, where the full pulse characterization is performed directly in the target region
Ptychographic reconstruction of attosecond pulses
Full text linkWe demonstrate a new attosecond pulse reconstruction modality which uses an algorithm that is derived from ptychography. In contrast to other methods, energy and delay sampling are not correlated, and as a result, the number of electron spectra to record is considerably smaller. Together with the robust algorithm, this leads to a more precise and fast convergence of the reconstruction
Attosecond dynamical Franz-Keldysh effect in polycrystalline diamond
Full text linkShort, intense laser pulses can be used to access the transition regime between classical and quantum optical responses in dielectrics. In this regime, the relative roles of inter- and intraband light-driven electronic transitions remain uncertain.We applied attosecond transient absorption spectroscopy to investigate the interaction between polycrystalline diamond and a few-femtosecond infrared pulse with intensity below the critical intensity of optical breakdown. Ab initio time-dependent density functional theory calculations, in tandem with a two-band parabolic model, accounted for the experimental results in the framework of the dynamical Franz-Keldysh effect and identified infrared induction of intraband currents as the main physical mechanism responsible for the observations
Combining attosecond XUV pulses with coincidence spectroscopy
Full text linkHere we present a successful combination of an attosecond beamline with a COLTRIMS apparatus, which we refer to as AttoCOLTRIMS. The setup provides either single attosecond pulses or attosecond pulse trains for extreme ultraviolet-infrared pump-probe experiments. We achieve full attosecond stability by using an active interferometer stabilization. The capability of the setup is demonstrated by means of two measurements, which lie at the heart of the COLTRIMS detector: firstly, we resolve the rotating electric field vector of an elliptically polarized few-cycle infrared laser field by attosecond streaking exploiting the access to the 3D momentum space of the charged particles. Secondly, we show streaking measurements on different atomic species obtained simultaneously in a single measurement making use of the advantage of measuring ions and electrons in coincidence. Both of these studies demonstrate the potential of the AttoCOLTRIMS for attosecond science
Access to phases of coherent phonon excitations by femtosecond ultraviolet photoelectron diffraction
Full text linkCoherent phonons are an excellent tool to investigate the interplay between electronic and structural dynamics. The displacive excitation of coherent phonons in elemental bismuth is one of the most widely studied processes for this purpose. We employ time-resolved photoelectron diffraction to access the structural dynamics by recording the photoemission intensity from one initial state as a function of emission angle. In comparison with tight-binding and single-scattering cluster calculations, this allows electronic and structural effects to be disentangled. Hence, the full dynamics of the hot electron gas and of coherently excited phonons can be accessed in a single experiment. As a major result the phase lag between the coherent phonons and the modulation of the electronic structure can be determined with high precision. The phonon phase lag with respect to the modulation of the electronic structure is about 2.85±0.21 rad, thus significantly smaller than π. The difference is not due to phonon decay by energy dissipation into low-energy modes, but rather caused by the very early evolution of the highly excited electron distribution
Economics of credence goods : the effect of monitoring and its costs in the health care market
No full textauthor: Lukas SchönerMasterarbeit University of Innsbruck 201
Economics of credence goods : the effect of monitoring and its costs in the health care market
No full textauthor: Lukas SchönerMasterarbeit University of Innsbruck 201
Tailoring comonomer incorporation in Ziegler-Natta based Linear Low Density Polyethylene
No full textAuthor DI Lukas GöpperlDissertation Johannes Kepler Universität Linz 202
Time-bin entangled photons from a quantum dot embedded in a nanowire
No full textauthor: Lukas Kirchner, BSc.Zusammenfassung in deutscher SpracheMasterarbeit University of Innsbruck 201
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