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Sci Rep 12, 19769 (2022)
Highly ordered laser imprinted plasmonic metasurfaces for polarization sensitive perfect absorption
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We present polarization-sensitive gap surface plasmon metasurfaces fabricated with direct material processing using pulsed laser light, an alternative and versatile approach. In particular we imprint laser induced periodic surface structures on nanometer-thick Ni films, which are back-plated by a grounded dielectric layer with TiO2 and ZnO deposition followed by Au evaporation. The procedure results in a metal-insulator-metal type plasmonic metasurface with a corrugated top layer consisting of highly-ordered, sinusoidal shaped, periodic, thin, metallic nanowires. The metasurface sustains sharp, resonant gap surface plasmons and provides various opportunities for polarization control in reflection, which is here switched by the size and infiltrating material of the insulating cavity. The polarization control is associated with the polarization sensitive perfect absorption and leads to high extinction ratios in the near-IR and mid-IR spectral areas. Corresponding Fourier-transform infrared spectroscopy measurements experimentally demonstrate that the fabrication approach produces metasurfaces with very well-defined, controllable, sharp resonances and polarization sensitive resonant absorption response which, depending on the insulating cavity size, impacts either the normal or the parallel to the nanowires polarization.
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Phys. Rev. Applied 18, 044009
All-Optical Generation and Time-Resolved Polarimetry of Magnetoacoustic Resonances via Transient Grating Spectroscopy
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The generation and control of surface acoustic waves (SAWs) in a magnetic material are objects of an intense research effort focused on magnetoelastic properties, with fruitful ramifications in spin-wave-based quantum logic and magnonics. We implement a transient grating setup to optically generate SAWs also seeding coherent spin waves via magnetoelastic coupling in ferromagnetic media. In this work we report on SAW-driven ferromagnetic resonance (FMR) experiments performed on polycrystalline Ni thin films in combination with time-resolved Faraday polarimetry, which allows extraction of the value of the effective magnetization and of the Gilbert damping. The results are in full agreement with measurements on the very same samples from standard FMR. Higher-order effects due to parametric modulation of the magnetization dynamics, such as down-conversion, up-conversion, and frequency mixing, are observed, testifying the high sensitivity of this technique.
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from our users
Journal of Alloys and Compounds, Volume 931, 10 January 2023, 167433
Microscopic mechanism of ferroelectric properties in barium hexaferrites
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The microscopic mechanism of the occurrence of ferroelectric properties in M-type barium hexaferrites is investigated by experimental and first-principle computation methods. The analysis of magnetic, X-ray, and Mössbauer measurements of BaFe12O19 samples ascertains the correlation between the thermal factor in the process of annealing samples and their functional properties. The occurrence of the remnant polarization in barium hexaferrites at room temperature contradicts the description of their crystal structure in the framework of centrosymmetric space group P63∕mmc (No. 194), in which one of the symmetry operations is inversion center. Therefore, the crystal structure of BaFe12O19 was analyzed in the frameworks of SG P63∕mmc (No. 194) and non-centrosymmetric SG P63mc (No. 186). The computed value of polarization for a non-centrosymmetric unit cell is ∼ 3.5 μC∕cm2. The analysis of polarization was carried out on a path connecting the polar P63mc and non-polar P63∕mmc structures and considered in terms of the total energy barrier. Our result allows ascertaining a direct relationship between the remnant polarization of the unit cell and the broken spatial-inversion symmetry in the crystal structure of M-type barium hexaferrite.
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Deliverables view all
WP12 - JA2 - X-ray Wavefront Metrology, Correction and Manipulation
D12.2 - Prototype of corrected CRL nanofocusing unit for user experiments
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Compound refractive lenses (CRLs) are widely used at synchrotron radiation facilities for X-ray beam shaping [1, 2] and focusing [3]. They are made by pressing a parabolic lens profile into a thin foil of aluminum or beryllium via a coining process. Their focusing capability depends on the manufacturing quality of the stamp and mechanical alignment during the coining process, both of which are limited by today’s technology [4]. Recently, diamond CRLs made by laser ablation and mechanical polishing emerged, which exhibit similar shape errors [5]. It has been shown that each lens shows a typical shape deviation of 500 nm from an ideal paraboloid of rotation [3]. When many of these lenses are stacked in order to create sub-micrometer X-ray beams, these shape errors add up and lead to spherical aberration, impacting the resolution and imaging capabilities of X-ray microscopes. A solution to overcome these challenges is the correction of aberration by an additional optical element, called a refractive phase plate [6]. It is tailor-made for the specific lens configuration and needs to be aligned with respect to the optical axis to within a few micrometers, requiring a motorization within a plane perpendicular to the optical axis. Here, we present the development of a new CRL lens holder with an integrated mechanism to align a phase plate and keep the aligned position over time and in between experimental campaigns in order to enable usability by non-expert users and to provide aberration-corrected nanobeams with CRLs within the NFFA catalogue for end users.
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WP1 - MGT1 - Project Management
D1.4 - First gender report
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Under Horizon 2020 gender is a cross-cutting issue and 3 objectives underpin the strategy on gender equality: 1. Fostering gender balance in research teams, in order to close the gaps in the participation of women. 2. Ensuring gender balance in decision-making, in order to reach the target of 40% of the under-represented sex in panels and groups and of 50% in advisory groups. 3. Integrating the gender dimension in research and innovation (R&I) content. In Horizon 2020 funded projects grant beneficiaries commit themselves to promoting equal opportunities and a balanced participation of women and men at all levels in research and innovation teams and in management structures. Moreover, gender balance is a feature of H2020 projects evaluated under Impact. This document aims at having a detailed snapshot of NEP performances about gender in the first 18 months from the beginning of the project, also in comparison with the numbers presented in SHE FIGURES 2021 (https://ec.europa.eu/assets/rtd/shefigures2021/index.html), and at identifying actions to pursue to better address gender issues outlined in NEP proposals.
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WP11 - JA1 - Real-time observation and control in microscopy and spectroscopy of nanoobjects
D11.2 - Pilot experiment carried out in collaboration with a FEL user facility
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The recent development of Free Electron Lasers (FELs) opens the way for pump-probe experiments in the extreme ultra violet (EUV) and X-Rays regime. In particular, seeded FELs are the best candidates for experiments in which high wavelength purity and power stability is required, such as coherent non-linear experiments. In this case, the fine control of photon energy and polarization is the key for accessing the dynamics of core level electrons in solid state systems, thanks to the species selectivity given by the variable photon energy of FEL pulses.
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Transnational Access Statistics
19 calls for access
646 proposals submitted
63% rate of acceptance
31% with Large Scale Facilities
13% with theory
12% with industry
~3 average users per proposal
58 countries applying
1924 lab sessions