Polarization contrast of nanoscale waveguides in high harmonic imaging

The optical polarization response of a structured material is one of its most significant properties, carrying information about microscopic anisotropies as well as chiral features and spin orientations. Polarization analysis is therefore a key element of imaging and spectroscopy techniques throughout the entire spectrum. In the case of extreme ultraviolet (EUV) radiation, however, both the preparation and detection of well-defined polarization states remain challenging. As a result, polarization-sensitive EUV microscopy based on table-top sources has not yet been realized, despite its great potential, for example, in nanoscale magnetic imaging. Here, we demonstrate polarization contrast in coherent diffractive imaging using high harmonic radiation and investigate the polarization properties of nanoscale transmission waveguides. We quantify the achievable polarization extinction ratio for different waveguide geometries and wavelengths. Our results demonstrate the utility of slab waveguides for efficient EUV polarization control and illustrate the importance of considering polarization contrast in the imaging of nanoscale structures

Toroidal grating astigmatism of high-harmonics characterized by EUV Hartmann sensor

The beam transport of single high-order harmonics in a monochromator arrangement is studied. A toroidal grating combines spectral filtering and focusing in order to produce a small individual spot for each harmonic. Here, the effect of small deviations from perfect alignment is investigated. Experimentally, a Hartmann sensor monitors the EUV wavefront while the grating is subjected to an online alignment procedure. The obtained results are confirmed by a simple theoretical description employing optical matrix methods

A dynamical symmetry triad in high-harmonic generation revealed by attosecond recollision control

A key element of optical spectroscopy is the link between observable selection rules and the underlying symmetries of an investigated physical system. Typically, selection rules directly relate to the sample properties probed by light, yielding information on crystalline structure or chirality, for example. Considering light-matter coupling more broadly may extend the scope of detectable symmetries, to also include those directly arising from the interaction. In this letter, we experimentally demonstrate an emerging class of symmetries in the electromagnetic field emitted by a strongly driven atomic system. Specifically, generating high-harmonic radiation with attosecond-controlled two-color fields, we find different sets of allowed and forbidden harmonic orders. Generalizing symmetry considerations of circularly polarized high-harmonic generation, we interpret these selection rules as a complete triad of dynamical symmetries. We expect such emergent symmetries also for multi-atomic and condensed-matter systems, encoded in the spectral and spatial features of the radiation field. Notably, the observed phenomenon gives robust access to chiral processes with few-attosecond time precision

Interlocked attosecond pulse trains in slightly bi-elliptical high harmonic generation

The ellipticity of high harmonics driven by bi-chromatic (e.g. w - 2w) fully tuned by varying the polarization of the pump components. In order to start revealing the underlying mechanism of this control, we explore a relatively simple regime of this scheme that still gives rise to full control over the harmonics ellipticities. In this regime, the pumps are only slightly elliptical and the high harmonic radiation consists of two (different) interlocked attosecond pulse trains (APTs). We formulate a semi-analytic model that maps the high harmonic ellipticity to properties of the APTs harmonic decompositions. Utilizing this model, we reconstruct these APTs variables from measurements of the high harmonics ellipticities. This ellipticity-resolved spectroscopy of interlocked APTs may be useful for ultrafast probing of chiral degrees of freedom

Coherent diffractive imaging beyond the projection approximation: Waveguiding at extreme ultraviolet wavelengths

We study extreme-ultraviolet wave propagation within optically thick nanostructures by means of high-resolution coherent diffractive imaging using high-harmonic radiation. Exit waves from different objects are reconstructed by phase retrieval algorithms, and are shown to be dominated by waveguiding within the sample. The experiments provide a direct visualization of extreme-ultraviolet guided modes, and demonstrate that multiple scattering is a generic feature in extruded nanoscale geometries. The observations are successfully reproduced in numerical and semi-analytical simulations

Nanoscale magnetic imaging using circularly polarized high-harmonic radiation

This work demonstrates nanoscale magnetic imaging using bright circularly polarized high-harmonic radiation. We utilize the magneto-optical contrast of worm-like magnetic domains in a Co/Pd multilayer structure, obtaining quantitative amplitude and phase maps by lensless imaging. A diffraction-limited spatial resolution of 49 nm is achieved with iterative phase reconstruction enhanced by a holographic mask. Harnessing the exceptional coherence of high harmonics, this approach will facilitate quantitative, element-specific, and spatially resolved studies of ultrafast magnetization dynamics, advancing both fundamental and applied aspects of nanoscale magnetism

2024 roadmap on magnetic microscopy techniques and their applications in materials science

Considering the growing interest in magnetic materials for unconventional computing, data storage, and sensor applications, there is active research not only on material synthesis but also characterisation of their properties. In addition to structural and integral magnetic characterisations, imaging of magnetisation patterns, current distributions and magnetic fields at nano- and microscale is of major importance to understand the material responses and qualify them for specific applications. In this roadmap, we aim to cover a broad portfolio of techniques to perform nano- and microscale magnetic imaging using superconducting quantum interference devices, spin centre and Hall effect magnetometries, scanning probe microscopies, x-ray- and electron-based methods as well as magnetooptics and nanoscale magnetic resonance imaging. The roadmap is aimed as a single access point of information for experts in the field as well as the young generation of students outlining prospects of the development of magnetic imaging technologies for the upcoming decade with a focus on physics, materials science, and chemistry of planar, three-dimensional and geometrically curved objects of different material classes including two-dimensional materials, complex oxides, semi-metals, multiferroics, skyrmions, antiferromagnets, frustrated magnets, magnetic molecules/nanoparticles, ionic conductors, superconductors, spintronic and spinorbitronic materials

Качество спермы быков красных пород ОАО племпредприятие «Барнаульское» и устойчивость её к криоконсервации

The characteristic of bulls-producers of red breeds of OAO Barnaulskoe breeding enterprise on the quality of sperm and its resistance to cryopreservation are presented. The breeding enterprise has examined samples of water, soil, feed for the content of heavy metals. In the studied samples, no excess of the LOC was found. The research results were processed on a PC using population statistics methods. Angler bulls produced the largest amount of ejaculates unsuitable for cryopreservation. It is 20.6%. According to this indicator, they surpassed the producers of red Danish and red steppe breeds by 4.1-7.8%. The animals of the latter breed showed the smallest amount (1.7%) of ejaculates rejected after defrost. In Angler bulls, this indicator was 5.95%, in red Danish bulls it was 2.95%, which is 3.52 and 1.75 times higher than in red steppe breeders (P <0.01-0.001). Significant differences were established between individual bulls of the red steppe breed in the number of ejaculates rejected before cryopreservation (2.84-22.29%) and after defrost (0-7.09%). The differences between breeds in the frequency of rejected ejaculates before freezing and after cryopreservation indicate a certain role of heredity in the resistance of animals for these indicators. Spearman’s rank correlation coefficient between these traits was 0.312. It indicates the possibility of preliminary assessment and selection of bulls according to the first indicator. But the final assessment of the bull-producers can be made by the frequency of rejected ejaculates after thawing. We propose to consider the issue of additional accounting in breeding programs for the resistance of the seed of bulls-producers to cryopreservation.Приведена характеристика быков-производителей красных пород ОАО Племпредприятие «Барнаульское» по качеству спермы и устойчивости её к криоконсервации. В районе разведения племпредприятия исследовали пробы воды, почвы, кормов на содержание тяжелых металлов. В изученных пробах не выявлено превышения ПДК. Результаты исследования обработаны на персональном компьютере с использованием популяционно-статистических методов. У быков англерской породы получено наибольшее количество эякулятов, непригодных для криоконсервации, составившее 20,6%. По этому показателю они превзошли на 4,1–7,8% производителей красной датской и красной степной пород. У животных последней породы выявлено наименьшее количество (1,7%) эякулятов, выбракованных после размораживания. У быков англерской породы этот показатель составил 5,95 %, у красных датских – 2,95 %, что в 3,52 и 1,75 раза выше по сравнению с красными степными производителями (P<0,01–0,001). Установлены значительные различия между отдельными быками красной степной породы по количеству выбракованных до криоконсервации эякулятов (2,84–22,29%) и после размораживания (0–7,09%). Различия между породами по частоте выбракованных эякулятов до замораживания и после криоконсервации свидетельствуют об определенной роли наследственности в устойчивости животных по этим показателям. Коэффициент ранговой корреляции Спирмена между этими признаками составил 0,312, что указывает на возможность предварительной оценки и отбора быков по первому показателю. Но окончательную оценку быка-производителя можно сделать по частоте выбракованных эякулятов после размораживания. Предлагается рассмотреть вопрос о дополнительном учете в селекционных программах устойчивости семени быков-производителей к криоконсервации

Observation of fluctuation-mediated picosecond nucleation of a topological phase

peer reviewedTopological states of matter exhibit fascinating physics combined with an intrinsic stability. A key challenge is the fast creation of topological phases, which requires massive reorientation of charge or spin degrees of freedom. Here we report the picosecond emergence of an extended topological phase that comprises many magnetic skyrmions. The nucleation of this phase, followed in real time via single-shot soft X-ray scattering after infrared laser excitation, is mediated by a transient topological fluctuation state. This state is enabled by the presence of a time-reversal symmetry-breaking perpendicular magnetic field and exists for less than 300 ps. Atomistic simulations indicate that the fluctuation state largely reduces the topological energy barrier and thereby enables the observed rapid and homogeneous nucleation of the skyrmion phase. These observations provide fundamental insights into the nature of topological phase transitions, and suggest a path towards ultrafast topological switching in a wide variety of materials through intermediate fluctuating states. © 2020, The Author(s), under exclusive licence to Springer Nature Limited.Leibniz Association Grant no. K162/2018 (OptiSPIN