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https://www.readbyqxmd.com/read/28747675/high-energy-mid-infrared-sub-cycle-pulse-synthesis-from-a-parametric-amplifier
#1
Houkun Liang, Peter Krogen, Zhou Wang, Hyunwook Park, Tobias Kroh, Kevin Zawilski, Peter Schunemann, Jeffrey Moses, Louis F DiMauro, Franz X Kärtner, Kyung-Han Hong
High-energy phase-stable sub-cycle mid-infrared pulses can provide unique opportunities to explore phase-sensitive strong-field light-matter interactions in atoms, molecules and solids. At the mid-infrared wavelength, the Keldysh parameter could be much smaller than unity even at relatively modest laser intensities, enabling the study of the strong-field sub-cycle electron dynamics in solids without damage. Here we report a high-energy sub-cycle pulse synthesiser based on a mid-infrared optical parametric amplifier and its application to high-harmonic generation in solids...
July 26, 2017: Nature Communications
https://www.readbyqxmd.com/read/28743976/nano-plasmonic-near-field-phase-matching-of-attosecond-pulses
#2
Tahir Shaaran, Rana Nicolas, Bianca Iwan, Milutin Kovacev, Hamed Merdji
Nano-structures excited by light can enhance locally the electric field when tuned to plasmonic resonances. This phenomenon can be used to boost non-linear processes such as harmonic generation in crystals or in gases, Raman excitation, and four wave mixing. Here we present a theoretical investigation of the near-field phase matching of attosecond pulses emitted by high-order harmonic generation (HHG) of an atom immersed in a multi-cycle femtosecond infrared laser field and a spatially inhomogeneous plasmonic field...
July 25, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28741594/polar-phase-transitions-in-heteroepitaxial-stabilized-la-sub-0-5-sub-y-sub-0-5-sub-alo-sub-3-sub-thin-films
#3
Shenghua Liu, Chunfeng Zhang, Mengya Zhu, Qian He, Jak Chakhalian, Xiaoran Liu, Albina Borisevich, Xiaoyong Wang, Min Xiao
We report on the fabrication of epitaxial La0.5Y0.5AlO3 ultrathin films on (001) LaAlO3 substrates. Structural characterizations by scanning transmission electron microscopy and X-ray diffraction confirm the high quality of the film with AlO6 octahedral tilt pattern. Unlike either of the nonpolar parent compound, LaAlO3 and YAlO3, second harmonic generation measurements on the thin films suggest a nonpolar - polar phase transition at Tc near 500 K, and a polar - polar phase transition at Ta near 160 K. By fitting the angular dependence of the second harmonic intensities, we further propose that the two polar structures can be assigned to the Pmc21 and Pmn21 space group, while the high temperature nonpolar structure belongs to the Pbnm space group...
July 25, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28736221/scaffold-curvature-mediated-novel-biomineralization-process-originates-a-continuous-soft-tissue-to-bone-interface
#4
Michael Paris, Andreas Götz, Inga Hettrich, Cécile M Bidan, John W C Dunlop, Hajar Razi, Ivo Zizak, Dietmar W Hutmacher, Peter Fratzl, Georg N Duda, Wolfgang Wagermaier, Amaia Cipitria
A myriad of shapes are found in biological tissues, often naturally evolved to fulfill a particular function. In the field of tissue engineering, substrate geometry influences cell behavior and tissue formation in-vitro, yet little is known how this translates to an in-vivo scenario. Here we investigate scaffold curvature-induced tissue growth, without additional growth factors or cells, in an ovine animal model. We show that soft tissue formation follows a curvature-driven tissue growth model. The highly organized endogenous soft matrix, potentially under mechanical strain, leads to a non-standard form of biomineralization, whereby the pre-existing organic matrix is mineralized without collagen remodeling and without an intermediate cartilage ossification phase...
July 20, 2017: Acta Biomaterialia
https://www.readbyqxmd.com/read/28733803/vocoder-simulations-explain-complex-pitch-perception-limitations-experienced-by-cochlear-implant-users
#5
Anahita H Mehta, Andrew J Oxenham
Pitch plays a crucial role in speech and music, but is highly degraded for people with cochlear implants, leading to severe communication challenges in noisy environments. Pitch is determined primarily by the first few spectrally resolved harmonics of a tone. In implants, access to this pitch is limited by poor spectral resolution, due to the limited number of channels and interactions between adjacent channels. Here we used noise-vocoder simulations to explore how many channels, and how little channel interaction, are required to elicit pitch...
July 21, 2017: Journal of the Association for Research in Otolaryngology: JARO
https://www.readbyqxmd.com/read/28731774/femtosecond-spin-current-pulses-generated-by-the-nonthermal-spin-dependent-seebeck-effect-and-interacting-with-ferromagnets-in-spin-valves
#6
Alexandr Alekhin, Ilya Razdolski, Nikita Ilin, Jan P Meyburg, Detlef Diesing, Vladimir Roddatis, Ivan Rungger, Maria Stamenova, Stefano Sanvito, Uwe Bovensiepen, Alexey Melnikov
Using the sensitivity of optical second harmonic generation to currents, we demonstrate the generation of 250-fs long spin current pulses in Fe/Au/Fe/MgO(001) spin valves. The temporal profile of these pulses indicates ballistic transport of hot electrons across a sub-100 nm Au layer. The pulse duration is primarily determined by the thermalization time of laser-excited hot carriers in Fe. Considering the calculated spin-dependent Fe/Au interface transmittance we conclude that a nonthermal spin-dependent Seebeck effect is responsible for the generation of ultrashort spin current pulses...
July 7, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28731095/polarization-driven-conductance-variations-at-charged-ferroelectric-domain-walls
#7
A-S Pawlik, T Kämpfe, A Haußmann, T Woike, U Treske, M Knupfer, B Büchner, E Soergel, R Streubel, A Koitzsch, L M Eng
Conducting domain walls (CDWs) in ferroelectric materials are promising candidates for applications in a manifold of nanoscale, optoelectronic devices. Characterization of their microscopic properties, however, remains challenging due to their small dimension and highly insulating environment. Here, we inspect individual CDWs in single-crystalline LiNbO3 by the combination of photoemission electron microscopy (PEEM) and second harmonic generation (SHG) microscopy. While SHG unveils the overall domain wall inclination angle α, PEEM is sensitive to local conductance variations, both at and away from the domain wall...
July 21, 2017: Nanoscale
https://www.readbyqxmd.com/read/28729510/tailored-semiconductors-for-high-harmonic-optoelectronics
#8
Murat Sivis, Marco Taucer, Giulio Vampa, Kyle Johnston, André Staudte, Andrei Yu Naumov, D M Villeneuve, Claus Ropers, P B Corkum
The advent of high-harmonic generation in gases 30 years ago set the foundation for attosecond science and facilitated ultrafast spectroscopy in atoms, molecules, and solids. We explore high-harmonic generation in the solid state by means of nanostructured and ion-implanted semiconductors. We use wavelength-selective microscopic imaging to map enhanced harmonic emission and show that the generation medium and the driving field can be locally tailored in solids by modifying the chemical composition and morphology...
July 21, 2017: Science
https://www.readbyqxmd.com/read/28714468/high-order-harmonic-generation-from-the-dressed-autoionizing-states
#9
M A Fareed, V V Strelkov, N Thiré, S Mondal, B E Schmidt, F Légaré, T Ozaki
In high-order harmonic generation, resonant harmonics (RH) are sources of intense, coherent extreme-ultraviolet radiation. However, intensity enhancement of RH only occurs for a single harmonic order, making it challenging to generate short attosecond pulses. Moreover, the mechanism involved behind such RH was circumstantial, because of the lack of direct experimental proofs. Here, we demonstrate the exact quantum paths that electron follows for RH generation using tin, showing that it involves not only the autoionizing state, but also a harmonic generation from dressed-AIS that appears as two coherent satellite harmonics at frequencies ±2Ω from the RH (Ω represents laser frequency)...
July 17, 2017: Nature Communications
https://www.readbyqxmd.com/read/28709984/micrometer-scale-guidance-of-mesenchymal-stem-cells-to-form-structurally-oriented-large-scale-tissue-engineered-cartilage
#10
Chih-Ling Chou, Alexander L Rivera, Valencia Williams, Jean F Welter, Joseph M Mansour, Judith A Drazba, Takao Sakai, Harihara Baskaran
Current clinical methods to treat articular cartilage lesions provide temporary relief of the symptoms but fail to permanently restore the damaged tissue. Tissue engineering, using mesenchymal stem cells (MSCs) combined with scaffolds and bioactive factors, is viewed as a promising method for repairing cartilage injuries. However, current tissue engineered constructs display inferior mechanical properties compared to native articular cartilage, which could be attributed to the lack of structural organization of the extracellular matrix (ECM) of these engineered constructs in comparison to the highly oriented structure of articular cartilage ECM...
July 11, 2017: Acta Biomaterialia
https://www.readbyqxmd.com/read/28708179/high-average-power-femtosecond-laser-at-258%C3%A2-%C3%A2-nm
#11
Michael Müller, Arno Klenke, Thomas Gottschall, Robert Klas, Carolin Rothhardt, Stefan Demmler, Jan Rothhardt, Jens Limpert, Andreas Tünnermann
We present an ultrafast fiber laser system delivering 4.6 W average power at 258 nm based on two-stage fourth-harmonic generation in beta barium borate (BBO). The beam quality is close to being diffraction limited with an M<sup>2</sup> value of 1.3×1.6. The pulse duration is 150 fs, which, potentially, is compressible down to 40 fs. A plain BBO and a sapphire-BBO compound are compared with respect to the achievable beam quality in the conversion process. This laser is applicable in scientific and industrial fields...
July 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28706258/transverse-coherence-limited-coherent-diffraction-imaging-using-a-molybdenum-soft-x-ray-laser-pumped-at-moderate-pump-energies
#12
M Zürch, R Jung, C Späth, J Tümmler, A Guggenmos, D Attwood, U Kleineberg, H Stiel, C Spielmann
Coherent diffraction imaging (CDI) in the extreme ultraviolet has become an important tool for nanoscale investigations. Laser-driven high harmonic generation (HHG) sources allow for lab scale applications such as cancer cell classification and phase-resolved surface studies. HHG sources exhibit excellent coherence but limited photon flux due poor conversion efficiency. In contrast, table-top soft X-ray lasers (SXRL) feature excellent temporal coherence and extraordinary high flux at limited transverse coherence...
July 13, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28701692/next-generation-driver-for-attosecond-and-laser-plasma-physics
#13
D E Rivas, A Borot, D E Cardenas, G Marcus, X Gu, D Herrmann, J Xu, J Tan, D Kormin, G Ma, W Dallari, G D Tsakiris, I B Földes, S-W Chou, M Weidman, B Bergues, T Wittmann, H Schröder, P Tzallas, D Charalambidis, O Razskazovskaya, V Pervak, F Krausz, L Veisz
The observation and manipulation of electron dynamics in matter call for attosecond light pulses, routinely available from high-order harmonic generation driven by few-femtosecond lasers. However, the energy limitation of these lasers supports only weak sources and correspondingly linear attosecond studies. Here we report on an optical parametric synthesizer designed for nonlinear attosecond optics and relativistic laser-plasma physics. This synthesizer uniquely combines ultra-relativistic focused intensities of about 10(20) W/cm(2) with a pulse duration of sub-two carrier-wave cycles...
July 12, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28698576/multimodal-imaging-quality-control-of-epithelia-regenerated-with-cultured-human-donor-corneal-limbal-epithelial-stem-cells
#14
Marco Lombardo, Sebastiano Serrao, Vanessa Barbaro, Enzo Di Iorio, Giuseppe Lombardo
Current imaging techniques for the characterization of differentiated corneal limbal stem cells are destructive and cannot be used in eye bank for monitoring the regenerated epithelium in culture. We presented a minimally invasive, multimodal, marker-free imaging method for the investigation of epithelia regenerated with cultured human donor corneal limbal epithelial stem cells. Two-photon fluorescence and harmonic generation signals were collected from specimens in culture and used for evaluating the structure and morphology of epithelia cultured on two different bio-scaffolds; in addition, donor human corneal tissues were used as controls...
July 11, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28694458/gamma-ray-vortices-from-nonlinear-inverse-thomson-scattering-of-circularly-polarized-light
#15
Yoshitaka Taira, Takehito Hayakawa, Masahiro Katoh
Inverse Thomson scattering is a well-known radiation process that produces high-energy photons both in nature and in the laboratory. Nonlinear inverse Thomson scattering occurring inside an intense light field is a process which generates higher harmonic photons. In this paper, we theoretically show that the higher harmonic gamma-ray produced by nonlinear inverse Thomson scattering of circularly polarized light is a gamma-ray vortex, which means that it possesses a helical wave front and carries orbital angular momentum...
July 10, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28692279/hot-electron-intraband-luminescence-from-gaas-nanospheres-mediated-by-magnetic-dipole-resonances
#16
Jin Xiang, Shuai Jiang, Jingdong Chen, Jinxiang Li, Qiaofeng Dai, Chengyun Zhang, Yi Xu, Shaolong Tie, Sheng Lan
Significantly enhanced electric field in plasmonic hot spots can dramatically increase the linear and nonlinear absorption of light, leading to a high-temperature electron gas which radiates, through mainly intraband transition, a broadband luminescence quite similar to blackbody radiation. Here, we demonstrate that such hot-electron intraband luminescence (HEIL) can also be achieved by exploiting the significantly enhanced electric field at the magnetic dipole resonances of gallium arsenide (GaAs) nanospheres (NSs)...
July 12, 2017: Nano Letters
https://www.readbyqxmd.com/read/28688444/ab-initio-lifetime-correction-to-scattering-states-for-time-dependent-electronic-structure-calculations-with-incomplete-basis-sets
#17
Emanuele Coccia, Roland Assaraf, Eleonora Luppi, Julien Toulouse
We propose a method for obtaining effective lifetimes of scattering electronic states for avoiding the artificial confinement of the wave function due to the use of incomplete basis sets in time-dependent electronic-structure calculations of atoms and molecules. In this method, using a fitting procedure, the lifetimes are extracted from the spatial asymptotic decay of the approximate scattering wave functions obtained with a given basis set. The method is based on a rigorous analysis of the complex-energy solutions of the Schrödinger equation...
July 7, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28687789/identification-of-stacking-faults-in-silicon-carbide-by-polarization-resolved-second-harmonic-generation-microscopy
#18
Radu Hristu, Stefan G Stanciu, Denis E Tranca, Efstathios K Polychroniadis, George A Stanciu
Although silicon carbide is a highly promising crystalline material for a wide range of electronic devices, extended and point defects which perturb the lattice periodicity hold deep implications with respect to device reliability. There is thus a great need for developing new methods that can detect silicon carbide defects which are detrimental to device functionality. Our experiment demonstrates that polarization-resolved second harmonic generation microscopy can extend the efficiency of the "optical signature" concept as an all-optical rapid and non-destructive set of investigation methods for the differentiation between hexagonal and cubic stacking faults in silicon carbide...
July 7, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28685879/agga2ps6-a-new-mid-infrared-nonlinear-optical-material-with-high-laser-damage-threshold-and-large-second-harmonic-generation-response
#19
Jiang-He Feng, Chun-Li Hu, Xiang Xu, Bing-Xuan Li, Ming-Jian Zhang, Jiang-Gao Mao
To develop new mid-infrared (MIR) nonlinear optical (NLO) materials, which can overcome the low laser damage threshold (LDT) of the commercial MIR-NLO crystals (AgGaS2, AgGaSe2 and ZnGeP2) and simultaneously keep the large NLO susceptibility, is urgent for the high-power MIR laser frequency conversion technology. To improve the LID, a new strategy of increasing lattice stability was adopted. Here, the strong covalent structural unit of PS4 tetrahedron was introduced into AgGaS2, and that led to the isolation of the first compound in Ag(I)-Ga(III)-P(V)-S system, namely, AgGa2PS6 (Cc)...
July 7, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28683102/identification-of-prognostic-collagen-signatures-and-potential-therapeutic-stromal-targets-in-canine-mammary-gland-carcinoma
#20
Ashley Case, Becky K Brisson, Amy C Durham, Suzanne Rosen, James Monslow, Elizabeth Buza, Pascale Salah, Julie Gillem, Gordon Ruthel, Sridhar Veluvolu, Veronica Kristiansen, Ellen Puré, Dorothy C Brown, Karin U Sørenmo, Susan W Volk
Increasing evidence indicates that the tumor microenvironment plays a critical role in regulating the biologic behavior of breast cancer. In veterinary oncology, there is a need for improved prognostic markers to accurately identify dogs at risk for local and distant (metastatic) recurrence of mammary gland carcinoma and therefore would benefit from adjuvant therapy. Collagen density and fiber organization have been shown to regulate tumor progression in both mouse and human mammary tumors, with certain collagen signatures predicting poor outcomes in women with breast cancer...
2017: PloS One
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