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2,801 results on '"Engel W"'

1. Nanoscale transient polarization gratings

Author

Foglia, Laura, Wehinger, Björn, Perosa, Giovanni, Mincigrucci, Riccardo, Allaria, Enrico, Armillotta, Francesco, Brynes, Alexander, Cucini, Riccardo, De Angelis, Dario, De Ninno, Giovanni, Engel, W. Dieter, Fainozzi, Danny, Giannessi, Luca, Khatu, Nupur N., Laterza, Simone, Paltanin, Ettore, Pelli-Cresi, Jacopo Stefano, Penco, Giuseppe, Puntel, Denny, Ribič, Primož Rebernik, Sottocorona, Filippo, Trovò, Mauro, Schmising, Clemens von Korff, Yao, Kelvin, Masciovecchio, Claudio, Bonetti, Stefano, and Bencivenga, Filippo

Subjects
Condensed Matter - Materials Science, Physics - Accelerator Physics, Physics - Optics
Abstract

We present the generation of transient polarization gratings at the nanoscale, achieved using a tailored accelerator configuration of the FERMI free electron laser. We demonstrate the capabilities of such a transient polarization grating by comparing its induced dynamics with the ones triggered by a more conventional intensity grating on a thin film ferrimagnetic alloy. While the signal of the intensity grating is dominated by the thermoelastic response of the system, such a contribution is suppressed in the case of the polarization grating. This exposes helicity-dependent magnetization dynamics that have so-far remained hidden under the large thermally driven response. We anticipate nanoscale transient polarization gratings to become useful for the study of any physical, chemical and biological systems possessing chiral symmetry.

Published
2023

2. Single-step fabrication of surface waveguides in fused silica with few-cycle laser pulses

Author

Furch, Federico J., Engel, W. Dieter, Witting, Tobias, Vrakking, Marc J. J., and Mermillod-Blondin, Alexandre

Subjects
Physics - Applied Physics, Physics - Optics
Abstract

Direct laser writing of surface waveguides with ultrashort pulses is a crucial achievement towards all-laser manufacturing of photonic integrated circuits sensitive to their environment. In this Letter, few-cycle laser pulses (with a sub-10 fs duration) are used to produce subsurface waveguides in a non-doped, non-coated fused silica substrate. The fabrication technique relies on laser-induced microdensification below the threshold for nanopore formation. The optical losses of the fabricated waveguides are governed by the optical properties of the superstrate. We have measured losses ranging from less than 0.1~dB/mm (air superstrate) up to 2.8~dB/mm when immersion oil is applied on top of the waveguide.

Published
2019
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3. Magneto-Optical Functions at the 3p resonances of Fe, Co, and Ni: Ab-initio description and experiment

Author

Willems, F., Sharma, S., Schmising, C. v. Korff, Dewhurst, J. K., Salemi, L., Schick, D., Hessing, P., Strüber, C., Engel, W. D., and Eisebitt, S.

Subjects
Condensed Matter - Materials Science
Abstract

We present theoretical and experimental data on the magneto-optical contributions to the complex refractive index in the extreme ultraviolet (XUV) range covering the 3p resonances of Fe, Co, and Ni. Comparing the spectra from density functional theory with magnetic circular dichroism measurements we find that many body corrections and local field efects are of crucial importance for accurate description of the spectra. Our results are relevant for the application of static XUV spectroscopy for multi element magnetic systems as well as for the investigation of ultrafast magnetization dynamics., Comment: 14 pages, 6 figures, incl. supplementary material

Published
2018
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8. Wide-field magneto-optical microscope to access quantitative magnetization dynamics with femtosecond temporal and sub-micrometer spatial resolution.

Author

Steinbach, F., Schick, D., von Korff Schmising, C., Yao, K., Borchert, M., Engel, W. D., and Eisebitt, S.

Subjects
MAGNETIZATION, MAGNETIC control, OPTICAL pumping, ABSOLUTE value, LIGHT intensity, FEMTOSECOND lasers, MICROSCOPES
Abstract

We introduce a wide-field magneto-optical microscope to probe magnetization dynamics with femtosecond temporal and sub-micrometer spatial resolution. We carefully calibrate the non-linear dependency between the magnetization of the sample and the detected light intensity by determining the absolute values of the magneto-optical polarization rotation. With that, an analytical transfer function is defined to directly map the recorded intensity to the corresponding magnetization, which results in significantly reduced acquisition times and relaxed computational requirements. The performance of the instrument is characterized by probing the magnetic all-optical switching dynamics of GdFe in a pump–probe experiment. The high spatial resolution of the microscope allows for accurately subdividing the laser-excited area into different fluence-regions in order to capture the strongly non-linear magnetization dynamics as a function of the optical pump intensity in a single measurement. [ABSTRACT FROM AUTHOR]

Published
2021
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12. Concept and Design of the SMART Spectromicroscope at BESSY II

Author

Engel, W., Degenhardt, R., Bradshaw, A. M., Erlebach, W., Ihmann, K., Kuhlenbeck, H., Wichtendahl, R., Freund, H.-J., Schlögl, R., Preikszas, D., Rose, H., Spehr, R., Hartel, P., Lilienkamp, G., Schmidt, Th., Bauer, E., Benner, G., Fink, R., Weiss, M. R., Umbach, E., Thieme, Jürgen, editor, Schmahl, Günter, editor, Rudolph, Dietbert, editor, and Umbach, Eberhard, editor

Published
1998
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35. From stripes to bubbles: Deterministic transformation of magnetic domain patterns in Co/Pt multilayers induced by laser helicity

Author

Novakovic-Marinkovic, N., Mawass, M.-A., Volkov, O., Makushko, P., Dieter Engel, W., Makarov, D., and Kronast, F.

Subjects
Magnetic domains, Magnetization switching, Multilayer thin films, Ferromagnetism, Physics::Optics, Ultrafast megnetic effects
Abstract

The optical control of magnetism offers an attractive possibility to manipulate small magnetic domains for prospective memory devices on ultrashort time scales. Here, we report on the local deterministic transformation of the magnetic domain pattern from stripes to bubbles in out-of-plane magnetized Co/Pt multilayers controlled only by the helicity of ultrashort laser pulses. Relying on the experimentally determined average size of stripe domains and the magnetic layer thickness, we calculate the temperature and characteristic fields at which the stripe-bubble transformation occurs. Furthermore, we demonstrate that in the narrow range of the laser power, the helicity induces a drag on domain walls.

Published
2020

45. Coeliac disease: in vivo toxicity of the putative immunodominant epitope

Author

Fraser, J.S., Engel, W., Ellis, H.J., Moodie, S.J., Pollock, E.L., Wieser, H., and Ciclitira, P.J.

Subjects
Blood cells -- Physiological aspects -- Genetic aspects -- Health aspects -- Research, Colorectal diseases -- Research -- Causes of -- Health aspects -- Care and treatment -- Genetic aspects, Antigenic determinants -- Physiological aspects -- Genetic aspects -- Research -- Health aspects, Interferon gamma -- Physiological aspects -- Genetic aspects -- Research, Toxins -- Physiological aspects -- Research -- Health aspects -- Genetic aspects, Patients -- Health aspects -- Care and treatment -- Physiological aspects -- Research, Amino acids -- Physiological aspects -- Health aspects -- Genetic aspects -- Research, Gastrointestinal diseases -- Research -- Causes of -- Health aspects -- Care and treatment -- Genetic aspects, Peptides -- Physiological aspects -- Genetic aspects -- Research -- Health aspects, Health, Care and treatment, Physiological aspects, Genetic aspects, Research, Health aspects, Causes of
Abstract

Gut 2003;52:1698-1702 Background: Peptides from α-gliadins have been used to characterise the immunodominant coeliac toxic epitope. A peptide corresponding to amino acid residues 57-73 of A-gliadin causes peripheral blood mononuclear [...]

Published
2003

46. Investigation of the putative immunodominant T cell epitopes in coeliac disease. (Coeliac Disease)

Author

Ellis, H.J., Pollock, E.L., Engel, W., Fraser, J.S., Rosen-Bronson, S., Wieser, H., and Ciclitira, P.J.

Subjects
Celiac disease -- Research, Health
Abstract

Background: Coeliac disease (CD) is an enteropathy mediated by gluten specific T cells which secrete interferan γ (IFN-γ) when stimulated by gluten peptides presented by HLA-DQ2 or DQ8 molecules. Residues [...]

Published
2003

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