| 1. |
- Schmising, Clemens von Korff, et al.
(författare)
-
Element-Specific Magnetization Dynamics of Complex Magnetic Systems Probed by Ultrafast Magneto-Optical Spectroscopy
- 2020
-
Ingår i: Applied Sciences. - : MDPI AG. - 2076-3417. ; 10:21
-
Tidskriftsartikel (refereegranskat)abstract
- The vision to manipulate and control magnetism with light is driven on the one hand by fundamental questions of direct and indirect photon-spin interactions, and on the other hand by the necessity to cope with ever growing data volumes, requiring radically new approaches on how to write, read and process information. Here, we present two complementary experimental geometries to access the element-specific magnetization dynamics of complex magnetic systems via ultrafast magneto-optical spectroscopy in the extreme ultraviolet spectral range. First, we employ linearly polarized radiation of a free electron laser facility to demonstrate decoupled dynamics of the two sublattices of an FeGd alloy, a prerequisite for all-optical magnetization switching. Second, we use circularly polarized radiation generated in a laboratory-based high harmonic generation setup to show optical inter-site spin transfer in a CoPt alloy, a mechanism which only very recently has been predicted to mediate ultrafast metamagnetic phase transitions.
|
|
| 2. |
- Vodungbo, Boris, et al.
(författare)
-
Indirect excitation of ultrafast demagnetization.
- 2016
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
-
Tidskriftsartikel (refereegranskat)abstract
- 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 laser pulse, the film exhibits the classical ultrafast demagnetization phenomenon although only a negligible number of IR photons penetrate the aluminum layer. In comparison with an uncapped cobalt/palladium reference film, the initial demagnetization of the capped film occurs with a delayed onset and at a slower rate. Both observations are qualitatively in line with energy transport from the aluminum layer into the underlying magnetic film by the excited, hot electrons of the aluminum film. Our data thus confirm recent theoretical predictions.
|
|
| 3. |
- Aziz, Emad F., et al.
(författare)
-
Cation-specific interactions with carboxylate in amino acid and acetate aqueous solutions : X-ray absorption and ab initio calculations
- 2008
-
Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 112:40, s. 12567-12570
-
Tidskriftsartikel (refereegranskat)abstract
- Relative interaction strengths between cations (X = Li+, Na+, K+, NH4+) and anionic carboxylate groups of acetate and glycine in aqueous solution are determined. These model systems mimic ion pairing of biologically relevant cations with negatively charged groups at protein surfaces. With oxygen ls X-ray absorption spectroscopy, we can distinguish between spectral contributions from H2O and carboxylate, which allows us to probe the electronic structure changes of the atomic site of the carboxylate group being closest to the countercation. From the intensity variations of the COOaq- ls X-ray absorption peak, which quantitatively correlate with the change in the local partial density of states from the carboxylic site, interactions are found to decrease in the sequence Na+ > Li+ > K+ > NH4+. This ordering, as well as the observed bidental nature of the -COOaq- and X-aq(+) interaction, is supported by combined ab initio and molecular dynamics calculations.
|
|
| 4. |
- Aziz, Emad F., et al.
(författare)
-
Photoinduced formation of N-2 molecules in ammonium compounds
- 2007
-
Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 111:39, s. 9662-9669
-
Tidskriftsartikel (refereegranskat)abstract
- Via fluorescence yield (FY) and resonant inelastic scattering spectroscopy in the soft X-ray range we find that soft X-rays induce formation of N-2 molecules in solid NH4Cl and in related compounds. The nitrogen molecules form weak bonds in NH4Cl, so that a substantial fraction of the molecules remains in the sample. From measurements of the FY as a function of exposure and temperature, the rates for the photochemical processes are estimated. At elevated temperatures (363 K), several nitrogen atoms are removed from the sample per incoming photon. At lower temperatures (233 K), the rate is reduced to around 0.02 nitrogen atoms for each incoming photon. Virtually all these atoms form N-2 molecules which are bound in the sample. The generality and implications of these results are briefly discussed.
|
|
| 5. |
- Durr, Hermann A., et al.
(författare)
-
A Closer Look Into Magnetism : Opportunities With Synchrotron Radiation
- 2009
-
Ingår i: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 45:1, s. 15-57
-
Forskningsöversikt (refereegranskat)abstract
- The unique properties of synchrotron radiation, such as broad energy spectrum, variable light polarization, and flexible time structure, have made it an enormously powerful tool in the study of magnetic phenomena and materials. The refinement of experimental techniques has led to many new research opportunities, keeping up with the challenges put up by modern magnetism research. In this contribution, we review some of the recent developments in the application of synchrotron radiation and particularly soft X-rays to current problems in magnetism, and we discuss future perspectives.
|
|
| 6. |
- Geilhufe, J., et al.
(författare)
-
Extracting depth information of 3-dimensional structures from a single-view X-ray Fourier-transform hologram
- 2014
-
Ingår i: Optics Express. - 1094-4087. ; 22:21, s. 24959-24969
-
Tidskriftsartikel (refereegranskat)abstract
- We demonstrate how information about the three-dimensional structure of an object can be extracted from a single Fourier-transform Xray hologram. In contrast to lens-based 3D imaging approaches that provide depth information of a specimen utilizing several images from different angles or via adjusting the focus to different depths, our method capitalizes on the use of the holographically encoded phase and amplitude information of the object's wavefield. It enables single-shot measurements of 3D objects at coherent X-ray sources. As the ratio of longitudinal resolution over transverse resolution scales proportional to the diameter of the reference beam aperture over the X-ray wavelength, we expect the approach to be particularly useful in the extreme ultraviolet and soft-X-ray regime. (C) 2014 Optical Society of America
|
|
| 7. |
- Hennecke, Martin, et al.
(författare)
-
Ultrafast opto-magnetic effects in the extreme ultraviolet spectral range
- 2024
-
Ingår i: Communications Physics. - : Springer Nature. - 2399-3650. ; 7:1
-
Tidskriftsartikel (refereegranskat)abstract
- Coherent light-matter interactions mediated by opto-magnetic phenomena like the inverse Faraday effect (IFE) are expected to provide a non-thermal pathway for ultrafast manipulation of magnetism on timescales as short as the excitation pulse itself. As the IFE scales with the spin-orbit coupling strength of the involved electronic states, photo-exciting the strongly spin-orbit coupled core-level electrons in magnetic materials appears as an appealing method to transiently generate large opto-magnetic moments. Here, we investigate this scenario in a ferrimagnetic GdFeCo alloy by using intense and circularly polarized pulses of extreme ultraviolet radiation. Our results reveal ultrafast and strong helicity-dependent magnetic effects which are in line with the characteristic fingerprints of an IFE, corroborated by ab initio opto-magnetic IFE theory and atomistic spin dynamics simulations.
|
|
| 8. |
- Hessing, Piet, et al.
(författare)
-
Holography-guided ptychography with soft X-rays
- 2016
-
Ingår i: Optics Express. - 1094-4087. ; 24:2, s. 1840-1851
-
Tidskriftsartikel (refereegranskat)abstract
- Ptychography is a lensless imaging technique that aims to reconstruct an object from a set of coherent diffraction patterns originating from different and partially overlapping sample illumination areas. For a successful convergence of the iterative algorithms used, the sample scan positions have to be known with very high accuracy. Here, we present a method that allows to directly encode this information in the diffraction patterns without the need of accurate position encoders. Our approach relies on combining ptychography with another coherent imaging method, namely Fourier-transform holography. We have imaged two different objects using coherent soft-X-ray illumination and investigate the influence of experimental and numerical position refinement on the reconstruction result. We demonstrate that holographically encoded positions significantly reduce the experimental and numerical requirements. Our ptychographic reconstructions cover a large field of view with diffraction-limited resolution and high sensitivity in the reconstructed phase shift and absorption of the objects.
|
|
| 9. |
- Malm, Erik, et al.
(författare)
-
Reference shape effects on Fourier transform holography
- 2022
-
Ingår i: Optics Express. - 1094-4087. ; 30:21, s. 38424-38438
-
Tidskriftsartikel (refereegranskat)abstract
- Soft-x-ray holography which utilizes an optics mask fabricated in direct contact with the sample, is a widely applied x-ray microscopy method, in particular, for investigating magnetic samples. The optics mask splits the x-ray beam into a reference wave and a wave to illuminate the sample. The reconstruction quality in such a Fourier-transform holography experiment depends primarily on the characteristics of the reference wave, typically emerging from a small, high-aspect-ratio pinhole in the mask. In this paper, we study two commonly used reference geometries and investigate how their 3D structure affects the reconstruction within an x-ray Fourier holography experiment. Insight into these effects is obtained by imaging the exit waves from reference pinholes via high-resolution coherent diffraction imaging combined with three-dimensional multislice simulations of the x-ray propagation through the reference pinhole. The results were used to simulate Fourier-transform holography experiments to determine the spatial resolution and precise location of the reconstruction plane for different reference geometries. Based on our findings, we discuss the properties of the reference pinholes with view on application in soft-x-ray holography experiments.
|
|
| 10. |
- Malm, Erik, et al.
(författare)
-
Singleshot polychromatic coherent diffractive imaging with a high-order harmonic source
- 2020
-
Ingår i: Optics Express. - 1094-4087. ; 28:1, s. 394-404
-
Tidskriftsartikel (refereegranskat)abstract
- 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 as input to extract the monochromatic sample diffraction pattern, then phase retrieval is performed on the quasi-monochromatic data to obtain the sample's exit surface wave. Reconstructions based on guided error reduction (ER) and alternating direction method of multipliers (ADMM) are compared. ADMM allows additional penalty terms to be included in the cost functional to promote sparsity within the reconstruction.
|
|
| 11. |
- Pancaldi, Matteo, 1989-, et al.
(författare)
-
Spiral metamaterials for terahertz magnetic field enhancement
- 2019
-
Ingår i: META 2019 Lisbon - Portugal. - : META Conference. ; , s. 1343-1344
-
Konferensbidrag (refereegranskat)abstract
- We designed a class of spiral thin-film antennas for enhancing, in the near field, the incident terahertz (THz) magnetic field. Indeed, using existing laser-based THz sources, our metamaterial geometry allows generating magnetic fields of the order of 2 T over a time scale of few picoseconds, enabling the investigation of nonlinear ultrafast spin dynamics in table-top experiments.
|
|
| 12. |
- Pfau, Bastian, et al.
(författare)
-
X-ray holography
- 2016
-
Ingår i: Synchrotron Light Sources and Free-Electron Lasers: Accelerator Physics, Instrumentation and Science Applications. - Cham : Springer International Publishing. - 9783319143934 - 9783319143941 ; , s. 1093-1133
-
Bokkapitel (refereegranskat)abstract
- With the dramatic increase in x-ray source brilliance and associated coherent photon flux, holography with x-rays has become feasible and is increasingly used for real-space investigations of static and dynamic properties of nanoscale systems. We describe the basic principles and capabilities of the method and present the current state of the art. A particular emphasis is put on the investigation of magnetic nanostructures, where x-ray holography has been applied at synchrotron radiation sources and free-electron x-ray lasers to investigate dynamic effects on time scales down to the femtosecond regime.
|
|
| 13. |
- Pfau, Bastian, et al.
(författare)
-
X-ray holography
- 2020
-
Ingår i: Synchrotron Light Sources and Free-Electron Lasers : Accelerator Physics, Instrumentation and Science Applications - Accelerator Physics, Instrumentation and Science Applications. - Cham : Springer International Publishing. - 9783030232009 - 9783030232016 ; , s. 1295-1335
-
Bokkapitel (refereegranskat)abstract
- With the dramatic increase in x-ray source brilliance and associated coherent photon flux, holography with x-rays has become feasible and is increasingly used for real-space investigations of static and dynamic properties of nanoscale systems. We describe the basic principles and capabilities of the method and present the current state of the art. A particular emphasis is put on the investigation of magnetic nanostructures, where x-ray holography has been applied at synchrotron radiation sources and free-electron x-ray lasers to investigate dynamic effects on time scales down to the femtosecond regime.
|
|
| 14. |
- Polley, Debanjan, et al.
(författare)
-
Terahertz magnetic field enhancement in an asymmetric spiral metamaterial
- 2018
-
Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 51:22
-
Tidskriftsartikel (refereegranskat)abstract
- 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 provide a simple analytical model that uses these geometrical parameters as input to give accurate estimates of the resonance frequency. Finite element simulations show that linearly polarized terahertz radiation efficiently couples to the MM thanks to the straight arm, inducing a current in the spiral, which in turn induces a resonant magnetic field enhancement at the center of the spiral. We observe a large (approximately 40 times) and uniform (over an area of similar to 10 mu m(2)) enhancement of the magnetic field for narrowband terahertz radiation with frequency matching the resonance frequency of the MM. When a broadband, single-cycle terahertz pulse propagates towards the MM, the peak magnetic field of the resulting band-passed waveform still maintains a six-fold enhancement compared to the peak impinging field. Using existing laser-based terahertz sources, our MM design allows to generate magnetic fields of the order of 2 T over a time scale of several picoseconds, enabling the investigation of nonlinear ultrafast spin dynamics in table-top experiments. Furthermore, our MM can be implemented to generate intense near-field narrowband, multi-cycle electromagnetic fields to study generic ultrafast resonant terahertz dynamics in condensed matter.
|
|
| 15. |
- Schmising, C. von Korff, et al.
(författare)
-
Imaging Ultrafast Demagnetization Dynamics after a Spatially Localized Optical Excitation
- 2014
-
Ingår i: Physical Review Letters. - 1079-7114. ; 111:21
-
Tidskriftsartikel (refereegranskat)abstract
- Ultrashort, coherent x-ray pulses of a free-electron laser are used to holographically image the magnetization dynamics within a magnetic domain pattern after creation of a localized excitation via an optical standing wave. We observe a spatially confined reduction of the magnetization within a couple of hundred femtoseconds followed by its slower recovery. Additionally, the experimental results show evidence of a spatial evolution of magnetization, which we attribute to ultrafast transport of nonequilibrium spin-polarized electrons for early times and to a fluence-dependent remagnetization rate for later times.
|
|
| 16. |
- Schmising, C. vonKorff, et al.
(författare)
-
Nonlocal ultrafast demagnetization dynamics of Co/Pt multilayers by optical field enhancement
- 2015
-
Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 17
-
Tidskriftsartikel (refereegranskat)abstract
- 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 interaction and time-dependent solutions of the coupled electron, lattice, and spin temperatures in two dimensions show good agreement with the experimental data, as well as giving evidence of non-local demagnetization dynamics due to electron diffusion.
|
|
| 17. |
- Schmitt, Thorsten, 1972-
(författare)
-
Resonant Soft X-Ray Emission Spectroscopy of Vanadium Oxides and Related Compounds
- 2004
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis addresses the electronic structure of vanadium and copper oxides using soft X-ray absorption (SXA) spectroscopy and resonant inelastic X-ray scattering (RIXS) at high brightness synchrotron radiation sources. In RIXS incident photons, tuned to the energy of specific absorption resonances, are inelastically scattered leaving behind a low energy valence excitation in the system studied. Effects of electron localization are reflected by the occurrence of low-energy excitations in form of dd- and charge-transfer excitations that are modelled by cluster calculations. Band-like states are dominating when the intermediate core excited state is delocalized.RIXS at V 2p and O 1s resonances has been used to study the electronic structure of the monovalent vanadium oxides VO2 and V2O3, and of the mixed valence compounds, NaV2O5 and V6O13. For NaV2O5 and V6O13 significant contributions from localized low-energy excitations reflect the partly localized character of their valence band electronic structure, whereas VO2 and V2O3 appear mostly as band-like. Effects of carrier doping are addressed for the case of Mo doping into VO2 and reveal a quasi-rigid band behavior. In the cases of VO2 and V6O13 the temperature dependent metal-insulator transition could be monitored by following the spectral evolution of bands originating from V 3d and V 3d - O2p hybridized states. For Na2V3O7 nanotubes it was possible to selectively probe states from the apical and the basal oxygen sites of VO5 pyramids that constitute these nanotubes. Furthermore, the RIXS technique has been demonstrated to be highly valuable in characterizing the charge transfer processes that accompany lithium insertion into vanadium oxide battery cathodes. Finally, for insulating cuprates RIXS at O 1s, Cu 3p and Cu 3s resonances has been recorded at high-resolution for the detailed investigation of crystal field excitations.
|
|
| 18. |
- Söderström, Johan, et al.
(författare)
-
Radiative decay spectra of selected doubly excited states in helium
- 2008
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 77:1, s. 012513-
-
Tidskriftsartikel (refereegranskat)abstract
- Radiative decay spectra of doubly excited states in He have been measured after selective excitation with monochromatized synchrotron radiation. The decay spectra are in excellent agreement with predictions based on calculations.
|
|
| 19. |
|
|
| 20. |
- Turenne, Diego, et al.
(författare)
-
Nonequilibrium sub–10 nm spin-wave soliton formation in FePt nanoparticles
- 2022
-
Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 8:13
-
Tidskriftsartikel (refereegranskat)abstract
- Magnetic nanoparticles such as FePt in the L10 phase are the bedrock of our current data storage technology. As the grains become smaller to keep up with technological demands, the superparamagnetic limit calls for materials with higher magnetocrystalline anisotropy. This, in turn, reduces the magnetic exchange length to just a few nanometers, enabling magnetic structures to be induced within the nanoparticles. Here, we describe the existence of spin-wave solitons, dynamic localized bound states of spin-wave excitations, in FePt nanoparticles. We show with time-resolved x-ray diffraction and micromagnetic modeling that spin-wave solitons of sub–10 nm sizes form out of the demagnetized state following femtosecond laser excitation. The measured soliton spin precession frequency of 0.1 THz positions this system as a platform to develop novel miniature devices.
|
|
| 21. |
- Zhou Hagström, Nanna, 1993-, et al.
(författare)
-
Megahertz-rate Ultrafast X-ray Scattering and Holographic Imaging at the European XFEL
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The advent of X-ray free-electron lasers (XFELs) has revolutionized fundamental science, from atomic to condensed matter physics, from chemistry to biology, giving researchers access to X-rays with unprecedented brightness, coherence, and pulse duration. All XFEL facilities built until recently provided X-ray pulses at a relatively low repetition rate, with limited data statistics. Here, we present the results from the first megahertz repetition rate X-ray scattering experiments at the Spectroscopy and Coherent Scattering (SCS) instrument of the European XFEL. We illustrate the experimental capabilities that the SCS instrument offers, resulting from the operation at MHz repetition rates and the availability of the novel DSSC 2D imaging detector. Time-resolved magnetic X-ray scattering and holographic imaging experiments in solid state samples were chosen as representative examples, providing an ideal test-bed for operation at megahertz rates. Nevertheless, our results are relevant and applicable to any other non-destructive XFEL experiments in the soft X-ray range.
|
|
| 22. |
- Zhou Hagström, Nanna, 1993-, et al.
(författare)
-
Megahertz-rate ultrafast X-ray scattering and holographic imaging at the European XFEL
- 2022
-
Ingår i: Journal of Synchrotron Radiation. - : International Union of Crystallography (IUCr). - 0909-0495 .- 1600-5775. ; 29, s. 1454-1464
-
Tidskriftsartikel (refereegranskat)abstract
- The advent of X-ray free-electron lasers (XFELs) has revolutionized fundamental science, from atomic to condensed matter physics, from chemistry to biology, giving researchers access to X-rays with unprecedented brightness, coherence and pulse duration. All XFEL facilities built until recently provided X-ray pulses at a relatively low repetition rate, with limited data statistics. Here, results from the first megahertz-repetition-rate X-ray scattering experiments at the Spectroscopy and Coherent Scattering (SCS) instrument of the European XFEL are presented. The experimental capabilities that the SCS instrument offers, resulting from the operation at megahertz repetition rates and the availability of the novel DSSC 2D imaging detector, are illustrated. Time-resolved magnetic X-ray scattering and holographic imaging experiments in solid state samples were chosen as representative, providing an ideal test-bed for operation at megahertz rates. Our results are relevant and applicable to any other non-destructive XFEL experiments in the soft X-ray range.
|
|
| 23. |
- Zhou Hagström, Nanna, 1993-
(författare)
-
Ultrafast spin dynamics at the nanoscale : using coherent X-ray and terahertz radiation
- 2022
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The field of ultrafast magnetism is driven by the growing need for faster and more efficient magnetic data storage, which comprises the vast majority of the digital information worldwide. However, after more than two decades of intense research, the understanding of the fundamental physical processes governing the transfer of angular momentum necessary for magnetic switching, is still lacking, partially hampered by the appropriate experimental tools. This situation is rapidly changing with the advent of X-ray free electron lasers (XFEL), which combine high temporal and spatial resolutions, necessary for a complete view of the physics at play. In the first work presented in this thesis, we demonstrate the capabilities of the recently built Spectroscopy and Coherent Scattering (SCS) instrument at the European XFEL. We perform ultrafast time-resolved small angle X-ray scattering (SAXS) on nanometre magnetic domains, combining ultrafast temporal resolution with high spatial resolution. We also demonstrate X-ray holographic reconstruction of similar magnetic domains. Our results show that the efficient data acquisition for holographic imaging is possible thanks to the MHz-operation of the European XFEL, paving the way for new studies and ultimately to create femtosecond movies of magnetism at the nanoscale. In the second work of this thesis, we describe a subsequent experiment at the SCS instrument, where we focus on the impact of symmetry breaking on the ultrafast dynamics of magnetic domains by looking at the diffracted SAXS data. Surprisingly, we observe a different ultrafast response depending on the anisotropy of the domains. We observe a clear contraction of the isotropic scattering ring in the reciprocal wavevector space (characteristic of randomly oriented domains), while no such contraction is observed in the anisotropic scattering pattern (distinctive of stripe-ordered domains). While the fundamental physical reason for the occurrence of the shift in wavevector space remains unexplained, we find that they correlate well with the domain symmetry. Our observation underlines the importance of symmetry as a critical variable for far-from-equilibrium dynamics. Finally, in the last work of the thesis, we look at the possibility of triggering ultrafast spin dynamics using intense THz magnetic field pulses. Typically, ultrafast spin dynamics is triggered using femtosecond lasers in the visible range. While readily available, these pulses cause highly non-equilibrium processes to take place because of the excitation energies in the eV range, comparable to the width of a typical electronic band. The potential excitation of all possible states within a band makes it difficult to disentangle which are the fundamental physical processes responsible for ultrafast demagnetization. On the other hand, radiation in the THz frequency range (meV energy range) directly couples to the magnetization without the risk of masking key processes. However, intense THz radiation is not easily generated because the relatively long wavelengths hamper the focusing capabilities due to the diffraction limit. To address this issue, we propose a metamaterial structure that enhances the THz magnetic field component of a free-space coupled THz field by more than one order of magnitude and exceeding the 1 T value. A table-top ultrafast time-resolved Faraday microscope setup with sub-micrometer resolution was built in order to investigate this experimentally.
|
|
