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https://www.readbyqxmd.com/read/27910350/optimization-and-application-of-cooled-avalanche-photodiodes-for-spectroscopic-fluctuation-measurements-with-ultra-fast-charge-exchange-recombination-spectroscopy
#1
D D Truong, R J Fonck, G R McKee
The Ultra-Fast Charge Exchange Recombination Spectroscopy (UF-CHERS) diagnostic is a highly specialized spectroscopic instrument with 2 spatial channels consisting of 8 spectral channels each and a resolution of ∼0.25 nm deployed at DIII-D to measure turbulent ion temperature fluctuations. Charge exchange emissions are obtained between 528 and 530 nm with 1 μs time resolution to study plasma instabilities. A primary challenge of extracting fluctuation measurements from raw UF-CHERS signals is photon and electronic noise...
November 2016: Review of Scientific Instruments
https://www.readbyqxmd.com/read/27910225/two-new-non-centrosymmetric-selenides-azn4in5se12-a-rb-cs-synthesis-characterization-and-nonlinear-optical-properties
#2
Liming Wu, Hua Lin, Yu-Jun Zheng, Xiao-Ning Hu, Hong Chen, Ju-Song Yu
Two new non-centrosymmetric polar quaternary selenides, namely, RbZn4In5Se12 and CsZn4In5Se12, have been synthesized and structurally characterized. They exhibit 3D diamond-like framework (DLF) consisting of corner shared MSe4 (M = Zn/In) tetrahedra, in which the A+ ions are located. Both compounds are thermally stable up to 1300 K and exhibit large transmittance in the infrared region (0.65-25 μm) with measured optical band gaps of 2.06 eV for RbZn4In5Se12 and 2.11 eV for CsZn4In5Se12. Inspiringly, they exhibit good balance between strong second harmonic generation (SHG) efficiency (3...
December 1, 2016: Chemistry, An Asian Journal
https://www.readbyqxmd.com/read/27906368/euv-scatterometer-with-a-high-harmonic-generation-euv-source
#3
Yi-Sha Ku, Chia-Liang Yeh, Yi-Chang Chen, Chun-Wei Lo, Wei-Ting Wang, Ming-Chang Chen
We have developed an extreme ultraviolet (EUV) scatterometer based on the analysis of coherent EUV light diffracted from a periodic array with nano-scale features. We discuss the choice of appropriate orders of the high harmonics generated coaxially along with the intense Ti:sapphire laser pulses for high resolution spatial performance. We describe an inverse-problem methodology for determining the structural parameters, and present preliminary measurement results confirming the functionality of the scatterometer...
November 28, 2016: Optics Express
https://www.readbyqxmd.com/read/27905565/evolution-of-structural-distortion-in-bifeo3-thin-films-probed-by-second-harmonic-generation
#4
Jie-Su Wang, Kui-Juan Jin, Hai-Zhong Guo, Jun-Xing Gu, Qian Wan, Xu He, Xiao-Long Li, Xiu-Lai Xu, Guo-Zhen Yang
BiFeO3 thin films have drawn much attention due to its potential applications for novel magnetoelectric devices and fundamental physics in magnetoelectric coupling. However, the structural evolution of BiFeO3 films with thickness remains controversial. Here we use an optical second-harmonic generation technique to explore the phase-related symmetry evolution of BiFeO3 thin films with the variation of thickness. The crystalline structures for 60 and 180-nm-thick BiFeO3 thin films were characterized by high-resolution X-ray diffractometry reciprocal space mapping and the local piezoelectric response for 60-nm-thick BiFeO3 thin films was characterized by piezoresponse force microscopy...
December 1, 2016: Scientific Reports
https://www.readbyqxmd.com/read/27898302/a-novel-sandwich-type-traveling-wave-piezoelectric-tracked-mobile-system
#5
Liang Wang, Chengyou Shu, Quan Zhang, Jiamei Jin
In this paper, a novel sandwich-type traveling wave piezoelectric tracked mobile system was proposed, designed, fabricated and experimentally investigated. The proposed system exhibits the advantages of simple structure, high mechanical integration, lack of electromagnetic interference, and lack of lubrication requirement, and hence shows potential application to robotic rovers for planetary exploration. The tracked mobile system is comprised of a sandwich actuating mechanism and a metal track. The actuating mechanism includes a sandwich piezoelectric transducer and two annular parts symmetrically placed at either end of the transducer, while the metal track is tensioned along the outer surfaces of the annular parts...
November 15, 2016: Ultrasonics
https://www.readbyqxmd.com/read/27895989/diet-induced-obesity-skin-changes-monitored-by-in-vivo-shg-and-ex-vivo-cars-microscopy
#6
Dóra Haluszka, Kende Lőrincz, Norbert Kiss, Róbert Szipőcs, Enikő Kuroli, Nóra Gyöngyösi, Norbert M Wikonkál
Obesity related metabolic syndrome and type 2 diabetes have severe consequences on our skin. Latest developments in nonlinear microscopy allow the use of noninvasive, label free imaging methods, such as second harmonic generation (SHG) and coherent anti-Stokes Raman scattering (CARS), for early diagnosis of metabolic syndrome-related skin complications by 3D imaging of the skin and the connective tissue. Our aim was to study effects of various types of diet-induced obesity in mice using these methods. We examined mice on different diets for 32 weeks...
November 1, 2016: Biomedical Optics Express
https://www.readbyqxmd.com/read/27895980/rapid-mesoscale-multiphoton-microscopy-of-human-skin
#7
Mihaela Balu, Hideharu Mikami, Jue Hou, Eric O Potma, Bruce J Tromberg
We present a multiphoton microscope designed for mesoscale imaging of human skin. The system is based on two-photon excited fluorescence and second-harmonic generation, and images areas of ~0.8x0.8 mm(2) at speeds of 0.8 fps (800x800 pixels; 12 frame averages) for high signal-to-noise ratio, with lateral and axial resolutions of 0.5µm and 3.3µm, respectively. The main novelty of this instrument is the design of the scan head, which includes a fast galvanometric scanner, optimized relay optics, a beam expander and high NA objective lens...
November 1, 2016: Biomedical Optics Express
https://www.readbyqxmd.com/read/27886492/role-of-excited-states-in-high-order-harmonic-generation
#8
S Beaulieu, S Camp, D Descamps, A Comby, V Wanie, S Petit, F Légaré, K J Schafer, M B Gaarde, F Catoire, Y Mairesse
We investigate the role of excited states in high-order harmonic generation by studying the spectral, spatial, and temporal characteristics of the radiation produced near the ionization threshold of argon by few-cycle laser pulses. We show that the population of excited states can lead either to direct extreme ultraviolet emission through free induction decay or to the generation of high-order harmonics through ionization from these states and recombination to the ground state. By using the attosecond lighthouse technique, we demonstrate that the high-harmonic emission from excited states is temporally delayed by a few femtoseconds compared to the usual harmonics, leading to a strong nonadiabatic spectral redshift...
November 11, 2016: Physical Review Letters
https://www.readbyqxmd.com/read/27883061/unravelling-the-dynamical-origin-of-below-and-near-threshold-harmonic-generation-of-h2-in-an-intense-nir-laser-field
#9
John Heslar, Shih-I Chu
Recently, the study of near- and below- threshold regime harmonics as a potential source of intense coherent vacuum-ultraviolet radiation has received considerable attention. However, the dynamical origin of these lower harmonics, particularly for the molecular systems, is less understood and largely unexplored. Here we perform the first fully ab initio and high precision 3D quantum study of the below- and near-threshold harmonic generation of molecules in an intense 800-nm near-infrared (NIR) laser field. Combining with a synchrosqueezing transform of the quantum time-frequency spectrum and an extended semiclassical analysis, we explore in-depth the roles of various quantum trajectories, including short- and long trajectories, multiphoton trajectories, resonance-enhanced trajectories, and multiple rescattering trajectories of the below- and near- threshold harmonic generation processes...
November 24, 2016: Scientific Reports
https://www.readbyqxmd.com/read/27881838/fabrication-of-ion-shaped-anisotropic-nanoparticles-and-their-orientational-imaging-by-second-harmonic-generation-microscopy
#10
Abdallah Slablab, Tero J Isotalo, Jouni Mäkitalo, Léo Turquet, Pierre-Eugène Coulon, Tapio Niemi, Christian Ulysse, Mathieu Kociak, Dominique Mailly, Giancarlo Rizza, Martti Kauranen
Ion beam shaping is a novel and powerful tool to engineer nanocomposites with effective three-dimensional (3D) architectures. In particular, this technique offers the possibility to precisely control the size, shape and 3D orientation of metallic nanoparticles at the nanometer scale while keeping the particle volume constant. Here, we use swift heavy ions of xenon for irradiation in order to successfully fabricate nanocomposites consisting of anisotropic gold nanoparticle that are oriented in 3D and embedded in silica matrix...
November 24, 2016: Scientific Reports
https://www.readbyqxmd.com/read/27873092/molecular-high-order-harmonic-spectra-and-its-application-to-the-generation-of-the-isolated-attosecond-pulse
#11
Li-Qiang Feng, Hang Liu, Wenliang Li, Rich-Samuel Castle
Molecular high-order harmonic generation (HHG) spectra from H2(+) and its application to the generation of the isolated attosecond pulses (IAPs) have been numerically investigated. Results show that (i) the 7th harmonic order is enhanced with the nuclei around the equilibrium internuclear, and as the internuclear distance increased, this enhanced harmonic produces a red-shift (even disappearance). Theoretical analyses show that the electronic transition between the ground and the 1st excited states is responsible for the red-shift enhanced harmonic...
December 2016: Journal of Molecular Modeling
https://www.readbyqxmd.com/read/27869832/generation-of-high-contrast-and-high-spatial-quality-idler-from-a-low-gain-optical-parametric-amplifier
#12
A B Sharba, G Nersisyan, M Zepf, N H Stuart, R A Smith, M Borghesi, G Sarri
The temporal contrast of a regeneratively amplified, sub-picosecond pulse is enhanced by employing a low-gain optical parametric amplification stage self-pumped by the second harmonic of the pulse. Through careful characterization of the two related nonlinear processes and optimization of the non-collinear geometry, a robust high-contrast idler pulse has been generated, with excellent spatial quality in both the near and far field. The overall energy conversion efficiency exceeds 14%, with 33% intensity conversion efficiency...
November 20, 2016: Applied Optics
https://www.readbyqxmd.com/read/27859706/structure-property-relationships-in-click-derived-donor-triazole-acceptor-materials
#13
Paul Kautny, Dorian Bader, Berthold Stöger, Georg A Reider, Johannes Fröhlich, Daniel Lumpi
To shed light on intramolecular charge-transfer phenomena in 1,2,3-triazole-linked materials, a series of 1,2,3-triazole-linked push-pull chromophores were prepared and studied experimentally and computationally. Investigated modifications include variation of donor and/or acceptor strength and linker moiety as well as regioisomers. Photophysical characterization of intramolecular charge-transfer features revealed ambipolar behavior of the triazole linker, depending on the substitution position. Furthermore, non-centrosymmetric materials were subjected to second-harmonic generation measurements, which revealed the high nonlinear optical activity of this class of materials...
November 15, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27858161/two-photon-optical-microscopy-imaging-of-endothelial-keratoplasty-grafts
#14
Marco Lombardo, Mohit Parekh, Sebastiano Serrao, Alessandro Ruzza, Stefano Ferrari, Giuseppe Lombardo
PURPOSE: To investigate the microstructure of endothelial keratoplasty grafts using two-photon optical microscopy. METHODS: Six endothelial keratoplasty grafts obtained from human donor corneoscleral tissues and prepared by submerged hydrodissection technique were imaged by two-photon optical microscopy. In each graft, two liquid bubbles were created in order to investigate the presence of a conserved cleavage plane regardless of the volume of posterior stroma that remained attached to Descemet's membrane (DM); the first bubble (bubble A) was generated under DM and the second bubble (bubble B) injection was done in order to obtain a layer of deep stroma that kept the two bubbles separated...
November 17, 2016: Graefe's Archive for Clinical and Experimental Ophthalmology
https://www.readbyqxmd.com/read/27857320/efficient-generation-of-1-9%C3%A2-%C3%A2-w-yellow-light-by-cascaded-frequency-doubling-of-a-distributed-bragg-reflector-tapered-diode
#15
A K Hansen, M Christensen, D Noordegraaf, P Heist, E Papastathopoulos, V Loyo-Maldonado, O B Jensen, P M W Skovgaard
Watt-level yellow emitting lasers are interesting for medical applications, due to their high hemoglobin absorption, and for efficient detection of certain fluorophores. In this paper, we demonstrate a compact and robust diode-based laser system in the yellow spectral range. The system generates 1.9 W of single-frequency light at 562.4 nm by cascaded single-pass frequency doubling of the 1124.8 nm emission from a distributed Bragg reflector (DBR) tapered laser diode. The absence of a free-space cavity makes the system stable over a base-plate temperature range of 30 K...
November 10, 2016: Applied Optics
https://www.readbyqxmd.com/read/27853775/molecular-frame-photoemission-by-a-comb-of-elliptical-high-order-harmonics-a-sensitive-probe-of-both-photodynamics-and-harmonic-complete-polarization-state
#16
K Veyrinas, V Gruson, S J Weber, L Barreau, T Ruchon, J-F Hergott, J-C Houver, R R Lucchese, P Salières, D Dowek
Due to the intimate anisotropic interaction between an XUV light field and a molecule resulting in photoionization (PI), molecular frame photoelectron angular distributions (MFPADs) are most sensitive probes of both electronic/nuclear dynamics and the polarization state of the ionizing light field. Consequently, they encode the complex dipole matrix elements describing the dynamics of the PI transition, as well as the three normalized Stokes parameters s1, s2, s3 characterizing the complete polarization state of the light, operating as molecular polarimetry...
November 17, 2016: Faraday Discussions
https://www.readbyqxmd.com/read/27828515/phenomenological-modeling-of-nonlinear-holograms-based-on-metallic-geometric-metasurfaces
#17
Weimin Ye, Xin Li, Juan Liu, Shuang Zhang
Benefiting from efficient local phase and amplitude control at the subwavelength scale, metasurfaces offer a new platform for computer generated holography with high spatial resolution. Three-dimensional and high efficient holograms have been realized by metasurfaces constituted by subwavelength meta-atoms with spatially varying geometries or orientations. Metasurfaces have been recently extended to the nonlinear optical regime to generate holographic images in harmonic generation waves. Thus far, there has been no vector field simulation of nonlinear metasurface holograms because of the tremendous computational challenge in numerically calculating the collective nonlinear responses of the large number of different subwavelength meta-atoms in a hologram...
October 31, 2016: Optics Express
https://www.readbyqxmd.com/read/27828495/pulse-sequences-for-efficient-multi-cycle-terahertz-generation-in-periodically-poled-lithium-niobate
#18
Koustuban Ravi, Damian N Schimpf, Franz X Kärtner
The use of laser pulse sequences to drive the cascaded difference frequency generation of high energy, high peak-power and multi-cycle terahertz pulses in cryogenically cooled (100 K) periodically poled Lithium Niobate is proposed and studied. Detailed simulations considering the coupled nonlinear interaction of terahertz and optical waves (or pump depletion), show that unprecedented optical-to-terahertz energy conversion efficiencies > 5%, peak electric fields of hundred(s) of mega volts/meter at terahertz pulse durations of hundred(s) of picoseconds can be achieved...
October 31, 2016: Optics Express
https://www.readbyqxmd.com/read/27828424/anomalous-circular-dichroism-in-high-harmonic-generation-of-stereoisomers-with-two-chiral-centers
#19
Xiaosong Zhu, Xi Liu, Pengfei Lan, Dian Wang, Qingbin Zhang, Wei Li, Peixiang Lu
When a molecule has more than one chiral center, it can be either a chiral molecule or a meso isomer. High harmonic generation (HHG) of stereoisomers with two chiral centers driven by circularly polarized (CP) laser pulses is investigated. Counterintuitively, it is found that the HHG exhibits prominent circular dichroism for the meso isomer, while the harmonic spectra with left and right CP laser pulses are nearly the same for the chiral isomers. We show that the anomalous circular dichroism is attributed to the characteristic recollision dynamics of HHG...
October 31, 2016: Optics Express
https://www.readbyqxmd.com/read/27828043/strong-electric-field-enhancements-in-asymmetric-metallic-nanostructures-and-high-order-harmonic-generation
#20
H Ebadian, M Mohebbi
Numerical investigation of high-order harmonic generation (HHG) is carried out in noble gases near metal nano-dimers. The effect of geometry, shape, and gap of the dimers in plasmon resonance and local electric field enhancement has been investigated numerically by using finite-difference time-domain methods. It is shown that a lack of symmetry in dimer shapes plays an important role in the HHG process, producing appreciable modifications to the energy-resolved photoelectron spectra.
October 1, 2016: Applied Optics
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