FG Röntgenoptik und Nanometer-Optik

24 Items

Recent Submissions
Nonlocal ultrafast demagnetization dynamics of Co/Pt multilayers by optical field enhancement

Korff Schmising, Clemens von ; Giovannella, M. ; Weder, David ; Schaffert, Stefan ; Webb, J. L. ; Eisebitt, Stefan (2015)

The influence on ultrafast demagnetization dynamics of metallic nano-structured gratings deposited on thin films of magnetic Co/Pt multilayers is investigated by the time-resolved optical Kerr effect. Depending on the polarization of the pump pulse, a pronounced enhancement of the demagnetization amplitude is found. Calculation of the inhomogeneous optical field distribution due to plasmon inte...

Mask-based dual-axes tomoholography using soft x-rays

Guehrs, Erik ; Fohler, Manuel ; Frömmel, Stefanie ; Günther, Christian M. ; Hessing, Piet ; Schneider, Michael ; Shemilt, Laura ; Eisebitt, Stefan (2015)

We explore tomographic mask-based Fourier transform x-ray holography with respect to the use of a thin slit as a reference wave source. This imaging technique exclusively uses the interference between the waves scattered by the object and the slit simplifying the experimental realization and ensuring high data quality. Furthermore, we introduce a second reference slit to rotate the sample aroun...

The UE49 SGM RICXS beamline at BESSY II

Pietzsch, Annette ; Eisebitt, Stefan (2016)

Beamline UE49 SGM is a dedicated high flux soft x ray beamline, spanning the energy range of 95 eV to 1400 eV. Its micrometer focus makes it ideally suitable for investigation of small or inhomogeneous samples both with spectroscopic methods and coherent scattering as well as imaging techniques with full polarization control.

Mechanical Design of the MID Split-and-Delay Line at the European XFEL

Friedrich, B. ; Noll, Tino ; Lu, Wei ; Roth, T. ; Madsen, Anders ; Eisebitt, Stefan (2016)

A new split-and-delay line (SDL) is under development for the Materials Imaging and Dynamics (MID) end station at the European XFEL.* The device utilises Bragg reflection to provide pairs of X-ray pulses with an energy of (5 - 10) keV and a continuously tunable time delay of (-10 - 800) ps - thus allowing zero-crossing of the time delay. The mechanical concept features separate positioning stag...

Multi-Color Imaging of Magnetic Co/Pt Multilayers

Weder, David ; Korff Schmising, Clemens von ; Willems, Felix ; Günther, Christian M. ; Schneider, Michael ; Pfau, Bastian ; Merhe, A. ; Jal, Emmanuelle ; Vodungbo, Boris ; Lüning, Jan ; Mahieu, B. ; Capotondi, F. ; Pedersoli, Emanuele ; Eisebitt, Stefan (2017)

We demonstrate for the first time the realization of a spatial resolved two color, element-specific imaging experiment at the free-electron laser facility FERMI. Coherent imaging using Fourier transform holography was used to achieve direct real space access to the nanometer length scale of magnetic domains of Co/Pt heterostructures via the element-specific magnetic dichroism in the extreme ult...

Achieving diffraction-limited resolution in soft-X-ray Fourier-transform holography

Geilhufe, Jan ; Pfau, Bastian ; Günther, Christian M. ; Schneider, Michael ; Eisebitt, Stefan (2020)

The spatial resolution of microscopic images acquired via X-ray Fourier-transform holography is limited by the source size of the reference wave and by the numerical aperture of the detector. We analyze the interplay between both influences and show how they are matched in practice. We further identify, how high spatial frequencies translate to imaging artifacts in holographic reconstructions w...

CAMP@FLASH: an end-station for imaging, electron- and ion-spectroscopy, and pump–probe experiments at the FLASH free-electron laser

Erk, Benjamin ; Müller, Jan P. ; Bomme, Cédric ; Boll, Rebecca ; Brenner, Günter ; Chapman, Henry N. ; Correa, Jonathan ; Düsterer, Stefan ; Dziarzhytski, Siarhei ; Eisebitt, Stefan ; Graafsma, Heinz ; Grunewald, Sören ; Gumprecht, Lars ; Hartmann, Robert ; Hauser, Günter ; Keitel, Barbara ; Korff Schmising, Clemens von ; Kuhlmann, Marion ; Manschwetus, Bastian ; Mercadier, Laurent ; Müller, Erland ; Passow, Christopher ; Plönjes, Elke ; Ramm, Daniel ; Rompotis, Dimitrios ; Rudenko, Artem ; Rupp, Daniela ; Sauppe, Mario ; Siewert, Frank ; Schlosser, Dieter ; Strüder, Lothar ; Swiderski, Angad ; Techert, Simone ; Tiedtke, Kai ; Tilp, Thomas ; Treusch, Rolf ; Schlichting, Ilme ; Ullrich, Joachim ; Moshammer, Robert ; Möller, Thomas ; Rolles, Daniel (2018)

The non-monochromatic beamline BL1 at the FLASH free-electron laser facility at DESY was upgraded with new transport and focusing optics, and a new permanent end-station, CAMP, was installed. This multi-purpose instrument is optimized for electron- and ion-spectroscopy, imaging and pump–probe experiments at free-electron lasers. It can be equipped with various electron- and ion-spectrometers, a...

Experimental evaluation of signal-to-noise in spectro-holography via modified uniformly redundant arrays in the soft x-ray and extreme ultraviolet spectral regime

Günther, Christian M. ; Guehrs, Erik ; Schneider, Michael ; Pfau, Bastian ; Korff Schmising, Clemens von ; Geilhufe, Jan ; Schaffert, Stefan ; Eisebitt, Stefan (2017)

We present dichroic x-ray lensless magnetic imaging by Fourier transform holography with an extended reference scheme via a modified uniformly redundant array (mURA). Holographic images of magnetic domains simultaneously generated by a single pinhole reference as well as by a mURA reference are compared with respect to the signal-to-noise ratio (SNR) as a function of exposure time. We apply thi...

Terahertz magnetic field enhancement in an asymmetric spiral metamaterial

Polley, Debanjan ; Hagström, Nanna Zhou ; Korff Schmising, Clemens von ; Eisebitt, Stefan ; Bonetti, Stefano (2018)

We use finite element simulations in both the frequency and the time-domain to study the terahertz resonance characteristics of a metamaterial (MM) comprising a spiral connected to a straight arm. The MM acts as a RLC circuit whose resonance frequency can be precisely tuned by varying the characteristic geometrical parameters of the spiral: inner and outer radius, width and number of turns. We ...

Indirect excitation of ultrafast demagnetization

Vodungbo, Boris ; Tudu, Bharati ; Perron, Jonathan ; Delaunay, Renaud ; Müller, Leonard ; Berntsen, Magnus H. ; Grübel, Gerhard ; Malinowski, Grégory ; Weier, Christian ; Gautier, Julien ; Lambert, Guillaume ; Zeitoun, Philippe ; Gutt, Christian ; Jal, Emmanuelle ; Reid, Alexander H. ; Granitzka, Patrick W. ; Jaouen, Nicolas ; Dakovski, Georgi L. ; Moeller, Stefan ; Minitti, Michael P. ; Mitra, Ankush ; Carron, Sebastian ; Pfau, Bastian ; Korff Schmising, Clemens von ; Schneider, Michael ; Eisebitt, Stefan ; Lüning, Jan (2016)

Does the excitation of ultrafast magnetization require direct interaction between the photons of the optical pump pulse and the magnetic layer? Here, we demonstrate unambiguously that this is not the case. For this we have studied the magnetization dynamics of a ferromagnetic cobalt/palladium multilayer capped by an IR-opaque aluminum layer. Upon excitation with an intense femtosecond-short IR ...

Optical inter-site spin transfer probed by energy and spin-resolved transient absorption spectroscopy

Willems, Felix ; Korff Schmising, Clemens von ; Strüber, Christian ; Schick, Daniel ; Engel, Dieter W. ; Dewhurst, J. K. ; Elliott, Peter ; Sharma, Sangeeta ; Eisebitt, Stefan (2020)

Optically driven spin transport is the fastest and most efficient process to manipulate macroscopic magnetization as it does not rely on secondary mechanisms to dissipate angular momentum. In the present work, we show that such an optical inter-site spin transfer (OISTR) from Pt to Co emerges as a dominant mechanism governing the ultrafast magnetization dynamics of a CoPt alloy. To demonstrate ...

In situ single-shot diffractive fluence mapping for X-ray free-electron laser pulses

Schneider, Michael ; Günther, Christian M. ; Pfau, Bastian ; Capotondi, Flavio ; Manfredda, Michele ; Zangrando, Marco ; Mahne, Nicola ; Raimondi, Lorenzo ; Pedersoli, Emanuele ; Naumenko, Denys ; Eisebitt, Stefan (2018)

Free-electron lasers (FELs) in the extreme ultraviolet (XUV) and X-ray regime opened up the possibility for experiments at high power densities, in particular allowing for fluence-dependent absorption and scattering experiments to reveal non-linear light–matter interactions at ever shorter wavelengths. Findings of such non-linear effects are met with tremendous interest, but prove difficult to ...

Generating circularly polarized radiation in the extreme ultraviolet spectral range at the free-electron laser FLASH

Korff Schmising, Clemens von ; Weder, David ; Noll, Tino ; Pfau, Bastian ; Hennecke, Martin ; Strüber, Christian ; Radu, Ilie ; Schneider, Michael ; Staeck, Steffen ; Günther, Christian M. ; Lüning, Jan ; Merhe, Alaa el Dine ; Buck, Jens ; Hartmann, Gregor ; Viefhaus, Jens ; Treusch, Rolf ; Eisebitt, Stefan (2017)

A new device for polarization control at the free electron laser facility FLASH1 at DESY has been commissioned for user operation. The polarizer is based on phase retardation upon reflection off metallic mirrors. Its performance is characterized in three independent measurements and confirms the theoretical predictions of efficient and broadband generation of circularly polarized radiation in t...

Multi-color imaging of magnetic Co/Pt heterostructures

Willems, Felix ; Korff Schmising, Clemens von ; Weder, David ; Günther, Christian M. ; Schneider, Michael ; Pfau, Bastian ; Meise, Sven ; Guehrs, Erik ; Geilhufe, Jan ; Merhe, Alaa El Din ; Jal, Emmanuelle ; Vodungbo, Boris ; Lüning, Jan ; Mahieu, Benoit ; Capotondi, Flavio ; Pedersoli, Emanuele ; Gauthier, David ; Manfredda, Michele ; Eisebitt, Stefan (2017)

We present an element specific and spatially resolved view of magnetic domains in Co/Pt heterostructures in the extreme ultraviolet spectral range. Resonant small-angle scattering and coherent imaging with Fourier-transform holography reveal nanoscale magnetic domain networks via magnetic dichroism of Co at the M2,3 edges as well as via strong dichroic signals at the O2,3 and N6,7 edges of Pt. ...

Singleshot polychromatic coherent diffractive imaging with a high-order harmonic source

Malm, Erik ; Wikmark, Hampus ; Pfau, Bastian ; Villanueva-Perez, Pablo ; Rudawski, Piotr ; Peschel, Jasper ; Maclot, Sylvain ; Schneider, Michael ; Eisebitt, Stefan ; Mikkelsen, Anders ; L’Huillier, Anne ; Johnsson, Per (2020-01-02)

Singleshot polychromatic coherent diffractive imaging is performed with a high-intensity high-order harmonic generation source. The coherence properties are analyzed and several reconstructions show the shot-to-shot fluctuations of the incident beam wavefront. The method is based on a multi-step approach. First, the spectrum is extracted from double-slit diffraction data. The spectrum is used a...

27 W 2.1 µm OPCPA system for coherent soft X-ray generation operating at 10 kHz

Feng, Tianli ; Heilmann, Anke ; Bock, Martin ; Ehrentraut, Lutz ; Witting, Tobias ; Yu, Haohai ; Stiel, Holger ; Eisebitt, Stefan ; Schnürer, Matthias (2020-03-11)

We developed a high power optical parametric chirped-pulse amplification (OPCPA) system at 2.1 µm harnessing a 500 W Yb:YAG thin disk laser as the only pump and signal generation source. The OPCPA system operates at 10 kHz with a single pulse energy of up to 2.7 mJ and pulse duration of 30 fs. The maximum average output power of 27 W sets a new record for an OPCPA system in the 2 µm wavelength ...

Pump-Probe X-ray Holographic Imaging of Dynamic Magnetization Processes Down to the Femtosecond Timescale

Eisebitt, Stefan (2015-09-23)

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Thermally induced magnetic switching in bit-patterned media

Pfau, Bastian ; Günther, Christian Michael ; Hauet, Thomas ; Eisebitt, Stefan ; Hellwig, O. (2017-07-31)

We have studied the thermal variation of the switching field of magnetic islands at room temperature. A model bit-pattern media composed of an assembly of islands with 80 nm width was fabricated by sputter deposition onto a pre-patterned substrate. Using direct magnetic-contrast imaging of the islands under applied field, we extract the switching probabilities of individual islands. Based on an...

Design and throughput simulations of a hard x-ray split and delay line for the MID station at the European XFEL

Lu, Wei ; Noll, T. ; Roth, T. ; Agapov, I. ; Geloni, G. ; Holler, M. ; Hallmann, J. ; Ansaldi, G. ; Eisebitt, Stefan ; Madsen, Anders (2016-07-27)

A hard X-ray Split and Delay Line (SDL) under development for the Materials Imaging and Dynamics (MID) station at the European X-Ray Free-Electron Laser (XFEL.EU) is presented. This device will provide pairs of X-ray pulses with a variable time delay ranging from −10 ps to 800 ps in a photon energy range from 5 to 10 keV. Throughput simulations in the SASE case indicate a total transmission of ...

Electric field modification of magnetotransport in Ni thin films on (011) PMN-PT piezosubstrates

Tkach, Alexander ; Kehlberger, Andreas ; Büttner, Felix ; Jakob, Gerhard ; Eisebitt, Stefan ; Kläui, Mathias (2015-02-10)

This study reports the magnetotransport and magnetic properties of 20 nm-thick polycrystalline Ni films deposited by magnetron sputtering on unpoled piezoelectric (011) [PbMg1/3Nb2/3O3]0.68-[PbTiO3]0.32 (PMN-PT) substrates. The longitudinal magnetoresistance (MR) of the Ni films on (011) PMN-PT, measured at room temperature in the magnetic field range of −0.3 T < μ0H < 0.3 T, is found to depend...