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https://www.readbyqxmd.com/read/28430252/measuring-spatiotemporal-ultrafast-field-structures-of-pulses-from-multimode-optical-fibers
#1
Zhe Guang, Michelle Rhodes, Rick Trebino
Ultrashort pulses emerging from multimode optical fibers are spatiotemporally complex, because inside these fibers the modes have different spatial intensity patterns and experience different propagation velocities and dispersions. To determine the spatiotemporal field from multimode fibers, we applied a technique for the complete measurement of the output pulses called a spatially and temporally resolved intensity and phase evaluation device: full information from a single hologram. It yields the complete electric field over space and time from multiple digital holograms, simultaneously recorded at different frequencies on a single camera frame...
April 20, 2017: Applied Optics
https://www.readbyqxmd.com/read/28429023/probing-the-role-of-excited-states-in-ionization-of-acetylene
#2
Daniel Dundas, Peter Mulholland, Abigail Wardlow, Alejandro de la Calle
Ionization of acetylene by linearly-polarized, vacuum ultraviolet (VUV) laser pulses is modelled using time-dependent density functional theory. Several laser wavelengths are considered including one that produces direct ionization to the first excited cationic state while another excites the molecules to a Rydberg series incorporating an autoionizing state. We show that for the wavelengths and intensities considered, ionization is greatest whenever the molecule is aligned along the laser polarization direction...
April 21, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28428549/low-noise-time-resolved-optical-sensing-of-electromagnetic-pulses-from-petawatt-laser-matter-interactions
#3
T S Robinson, F Consoli, S Giltrap, S J Eardley, G S Hicks, E J Ditter, O Ettlinger, N H Stuart, M Notley, R De Angelis, Z Najmudin, R A Smith
We report on the development and deployment of an optical diagnostic for single-shot measurement of the electric-field components of electromagnetic pulses from high-intensity laser-matter interactions in a high-noise environment. The electro-optic Pockels effect in KDP crystals was used to measure transient electric fields using a geometry easily modifiable for magnetic field detection via Faraday rotation. Using dielectric sensors and an optical fibre-based readout ensures minimal field perturbations compared to conductive probes and greatly limits unwanted electrical pickup between probe and recording system...
April 20, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28427634/enhanced-porosity-and-permeability-of-three-dimensional-alginate-scaffolds-via-acoustic-microstreaming-induced-by-low-intensity-pulsed-ultrasound
#4
Gepu Guo, Yong Ma, Yang Guo, Chunbing Zhang, Xiasheng Guo, Juan Tu, Alfred C H Yu, Junru Wu, Dong Zhang
The shear stress resulting from the microstreaming induced by low-intensity pulsed ultrasound (LIPUS) has been often used to improve the permeability of cell membrane or porous engineering scaffolds. In the present study, three-dimensional (3-D) scaffold culture systems were constituted to simulate the in vivo microenvironment, providing benefits for cell growth. In order to investigate the mechanism underlying the enhanced porosity and permeability of the 3-D alginate scaffolds by using LIPUS with varied acoustic intensities, two quantitative imaging techniques (i...
July 2017: Ultrasonics Sonochemistry
https://www.readbyqxmd.com/read/28419322/dosimetric-evaluation-of-laser-driven-x-ray-and-neutron-sources-utilizing-xg-iii-ps-laser-with-peak-power-of-300-terawatt
#5
Bo Yang, Rui Qiu, Jinlong Jiao, Wei Lu, Zhimeng Zhang, Weimin Zhou, Chi Ma, Hui Zhang, Junli Li
Current short-pulse high-intensity lasers can accelerate electrons and proton/ions to energies of giga-electron volts. For certain advanced applications, laser-accelerated electrons and protons are optimised for high-energy X-ray and neutron generation at the XG-III picosecond (ps) laser beamline. These energetic X-ray and neutron beams can significantly affect radiation safety at the facility; therefore, proper evaluation of the radiological hazards induced by laser-driven X-ray and neutron sources is required...
April 13, 2017: Radiation Protection Dosimetry
https://www.readbyqxmd.com/read/28418264/emission-characteristics-of-laser-induced-plasma-using-collinear-long-and-short-dual-pulse-laser-induced-breakdown-spectroscopy-libs
#6
Zhenzhen Wang, Yoshihiro Deguchi, Renwei Liu, Akihiro Ikutomo, Zhenzhen Zhang, Daotong Chong, Junjie Yan, Jiping Liu, Fang-Jung Shiou
Collinear long and short dual-pulse laser-induced breakdown spectroscopy (DP-LIBS) was employed to clarify the emission characteristics from laser-induced plasma. The plasma was sustained and became stable by the long pulse-width laser with the pulse width of 60 μs under free running (FR) conditions as an external energy source. Comparing the measurement results of stainless steel in air using single-pulse LIBS (SP-LIBS) and DP-LIBS, the emission intensity was markedly enhanced using DP-LIBS. The temperature of plasma induced by DP-LIBS was maintained at a higher temperature under different gate delay time and short pulse-width laser power conditions compared with those measured using short SP-LIBS...
January 1, 2017: Applied Spectroscopy
https://www.readbyqxmd.com/read/28418076/ultrasonic-modulation-of-tissue-optical-properties-in-ex-vivo-porcine-skin-to-improve-transmitted-transdermal-laser-intensity
#7
Paul J D Whiteside, Chenxi Qian, Nicholas Golda, Heather K Hunt
BACKGROUND AND OBJECTIVE: Applications of light-based energy devices involving optical targets within the dermis frequently experience negative side-effects resultant from surface scattering and excess optical absorption by epidermal melanin. As a broadband optical absorber, melanin decreases the efficacy of light-based treatments throughout the ultraviolet, visible, and near-infrared spectra while also generating additional heat within the surface tissue that can lead to inflammation or tissue damage...
April 18, 2017: Lasers in Surgery and Medicine
https://www.readbyqxmd.com/read/28415304/measurement-of-the-equation-of-state-of-solid-density-copper-heated-with-laser-accelerated-protons
#8
S Feldman, G Dyer, D Kuk, T Ditmire
We present equation of state (EOS) measurements of solid-density copper heated to 5-10 eV. A copper sample was heated isochorically by hydrogen ions accelerated from an adjacent foil by a high intensity pulsed laser, and probed optically. The measured temperature and expansion are compared against simulations using the most up-to-date wide range EOS tables available.
March 2017: Physical Review. E
https://www.readbyqxmd.com/read/28415266/cavitation-and-spallation-in-liquid-metal-droplets-produced-by-subpicosecond-pulsed-laser-radiation
#9
M S Krivokorytov, A Yu Vinokhodov, Yu V Sidelnikov, V M Krivtsun, V O Kompanets, A A Lash, K N Koshelev, V V Medvedev
The deformation and fragmentation of liquid metal microdroplets by intense subpicosecond Ti:sapphire laser pulses is experimentally studied with stroboscopic shadow photography. The experiments are performed at a peak intensity of 10^{14}W/cm^{2} at the target's surface, which produces shock waves with pressures in the Mbar range. As a result of such a strong impact, the droplet is transformed into a complex-shaped hollow structure that undergoes asymmetrical expansion and eventually fragments. The hollow structure of the expanding target is explained by the effects of cavitation and spallation that follow the propagation of the laser-induced shock wave...
March 2017: Physical Review. E
https://www.readbyqxmd.com/read/28414363/signal-restoration-method-for-restraining-the-range-walk-error-of-geiger-mode-avalanche-photodiode-lidar-in-acquiring-a-merged-three-dimensional-image
#10
Lu Xu, Yu Zhang, Yong Zhang, Long Wu, Chenghua Yang, Xu Yang, Zijing Zhang, Yuan Zhao
The fluctuation in the number of signal photoelectrons will cause a range walk error in a Geiger-mode avalanche photodiode (Gm-APD) lidar, which significantly depends on the target intensity. For a nanosecond-pulsed laser, the range walk error of traditional time-of-flight will cause deterioration. A new signal restoration method, based on the Poisson probability response model and the center-of-mass algorithm, is proposed to restrain the range walk error. We obtain a high-precision depth and intensity merged 3D image using this method...
April 10, 2017: Applied Optics
https://www.readbyqxmd.com/read/28414341/laser-induced-atomic-emission-of-silicon-nanoparticles-during-laser-induced-heating
#11
Jan Menser, Kyle Daun, Thomas Dreier, Christof Schulz
The temporal luminescence behavior of silicon atoms during and after laser-heating of gas-borne silicon nanoparticles was investigated. Silicon nanoparticles were formed in the exhaust stream of a microwave plasma reactor at 100 mbar. The observed prompt atomic line intensities correspond with thermal excitation of the evaporated species. A prompt signal at 251.61 and 288.15 nm originating from the 3s<sup>2</sup>3p<sup>2</sup>→3s<sup>2</sup>3p4s transitions showed a lifetime of 16 ns that matches the documented excited-state lifetime for the respective transitions...
April 10, 2017: Applied Optics
https://www.readbyqxmd.com/read/28414231/organic-phosphorescence-nanowire-lasers
#12
Zhenyi Yu, Yishi Wu, Lu Xiao, Jianwei Chen, Qing Liao, Jiannian Yao, Hongbing Fu
Organic solid-state lasers (OSSLs) based on singlet fluorescence have merited intensive study as an important class of light sources. Although the use of triplet phosphors has led to 100% internal quantum efficiency in organic light emitting diodes (OLEDs), stumbling blocks in triplet lasing include generally forbidden intersystem crossing (ISC) and low quantum yield of phosphorescence (ΦP). Here, we reported the first triplet-phosphorescence OSSL from nanowire microcavity of a sulfide-substituted difluoroboron compound...
April 17, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28413806/ryanodine-and-ip3-receptor-mediated-calcium-signaling-play-a-pivotal-role-in-neurological-infrared-laser-modulation
#13
Gleb P Tolstykh, Cory A Olsovsky, Bennett L Ibey, Hope T Beier
Pulsed infrared (IR) laser energy has been shown to modulate neurological activity through both stimulation and inhibition of action potentials. While the mechanism(s) behind this phenomenon is (are) not completely understood, certain hypotheses suggest that the rise in temperature from IR exposure could activate temperature- or pressure-sensitive ion channels or create pores in the cellular outer membrane, allowing an influx of typically plasma-membrane-impermeant ions. Studies using fluorescent intensity-based calcium ion ([Formula: see text]) sensitive dyes show changes in [Formula: see text] levels after various IR stimulation parameters, which suggests that [Formula: see text] may originate from the external solution...
April 2017: Neurophotonics
https://www.readbyqxmd.com/read/28411595/infrared-absorption-of-methanol-water-clusters-ch3oh-n-h2o-n-1-4-recorded-with-the-vuv-ionization-ir-depletion-technique
#14
Yu-Fang Lee, Anne-Marie Kelterer, Gergely Matisz, Sándor Kunsági-Máté, Chao-Yu Chung, Yuan-Pern Lee
We recorded infrared (IR) spectra in the CH- and OH-stretching regions of size-selected clusters of methanol (M) with one water molecule (W), represented as MnW, n = 1-4, in a pulsed supersonic jet using the photoionization/IR-depletion technique. Vacuum ultraviolet emission at 118 nm served as the source of ionization in a time-of-flight mass spectrometer to detect clusters MnW as protonated forms Mn-1WH(+). The variations in intensities of Mn-1WH(+) were monitored as the wavelength of the IR laser light was tuned across the range 2700-3800 cm(-1)...
April 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28409970/observation-of-betatron-x-ray-radiation-in-a-self-modulated-laser-wakefield-accelerator-driven-with-picosecond-laser-pulses
#15
F Albert, N Lemos, J L Shaw, B B Pollock, C Goyon, W Schumaker, A M Saunders, K A Marsh, A Pak, J E Ralph, J L Martins, L D Amorim, R W Falcone, S H Glenzer, J D Moody, C Joshi
We investigate a new regime for betatron x-ray emission that utilizes kilojoule-class picosecond lasers to drive wakes in plasmas. When such laser pulses with intensities of ∼5×10^{18}  W/cm^{2} are focused into plasmas with electron densities of ∼1×10^{19}  cm^{-3}, they undergo self-modulation and channeling, which accelerates electrons up to 200 MeV energies and causes those electrons to emit x rays. The measured x-ray spectra are fit with a synchrotron spectrum with a critical energy of 10-20 keV, and 2D particle-in-cell simulations were used to model the acceleration and radiation of the electrons in our experimental conditions...
March 31, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28401940/optical-nonlinearity-enhancement-with-graphene-decorated-silicon-waveguides
#16
Atsushi Ishizawa, Rai Kou, Takahiro Goto, Tai Tsuchizawa, Nobuyuki Matsuda, Kenichi Hitachi, Tadashi Nishikawa, Koji Yamada, Tetsuomi Sogawa, Hideki Gotoh
Broadband on-chip optical frequency combs (OFCs) are important for expanding the functionality of photonic integrated circuits. Here, we demonstrate a huge local optical nonlinearity enhancement using graphene. A waveguide is decorated with graphene by precisely manipulating graphene's area and position. Our approach simultaneously achieves both an extremely efficient supercontinuum and ultra-short pulse generation. With our graphene-decorated silicon waveguide (G-SWG), we have achieved enhanced spectral broadening of femtosecond pump pulses, along with an eightfold increase in the output optical intensity at a wavelength approximately 200 nm shorter than that of the pump pulses...
April 12, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28401413/concentration-dependent-approach-for-accurate-determination-of-two-photon-absorption-cross-section-of-fluorescent-dye-molecule
#17
Sandeep Kumar Maurya, Chayan Dutta, Debabrata Goswami
We have investigated the concentration dependent of two-photon induced fluorescence (TPIF) in methanolic solution of Rhodamine 6G and Rhodamine B dye using 120 fs laser pulses at 780 nm, 76 MHz repetition rate. TPIF study of these dyes was compared with their respective one photon fluorescence intensity. We have shown the effect of chopper on TPIF intensity from Rhodamine dyes, which have shown direct influence on the determined TPA Cross section of these dyes.
April 11, 2017: Journal of Fluorescence
https://www.readbyqxmd.com/read/28398334/diffraction-data-of-core-shell-nanoparticles-from-an-x-ray-free-electron-laser
#18
Xuanxuan Li, Chun-Ya Chiu, Hsiang-Ju Wang, Stephan Kassemeyer, Sabine Botha, Robert L Shoeman, Robert M Lawrence, Christopher Kupitz, Richard Kirian, Daniel James, Dingjie Wang, Garrett Nelson, Marc Messerschmidt, Sébastien Boutet, Garth J Williams, Elisabeth Hartmann, Aliakbar Jafarpour, Lutz M Foucar, Anton Barty, Henry Chapman, Mengning Liang, Andreas Menzel, Fenglin Wang, Shibom Basu, Raimund Fromme, R Bruce Doak, Petra Fromme, Uwe Weierstall, Michael H Huang, John C H Spence, Ilme Schlichting, Brenda G Hogue, Haiguang Liu
X-ray free-electron lasers provide novel opportunities to conduct single particle analysis on nanoscale particles. Coherent diffractive imaging experiments were performed at the Linac Coherent Light Source (LCLS), SLAC National Laboratory, exposing single inorganic core-shell nanoparticles to femtosecond hard-X-ray pulses. Each facetted nanoparticle consisted of a crystalline gold core and a differently shaped palladium shell. Scattered intensities were observed up to about 7 nm resolution. Analysis of the scattering patterns revealed the size distribution of the samples, which is consistent with that obtained from direct real-space imaging by electron microscopy...
April 11, 2017: Scientific Data
https://www.readbyqxmd.com/read/28390366/dynamics-of-photoionization-from-molecular-electronic-wavepacket-states-in-intense-pulse-laser-fields-a-nonadiabatic-electron-wavepacket-study
#19
Takahide Matsuoka, Kazuo Takatsuka
A theory for dynamics of molecular photoionization from nonadiabatic electron wavepackets driven by intense pulse lasers is proposed. Time evolution of photoelectron distribution is evaluated in terms of out-going electron flux (current of the probability density of electrons) that has kinetic energy high enough to recede from the molecular system. The relevant electron flux is in turn evaluated with the complex-valued electronic wavefunctions that are time evolved in nonadiabatic electron wavepacket dynamics in laser fields...
April 7, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28389668/photoacoustic-imaging-reveals-hidden-underdrawings-in-paintings
#20
George J Tserevelakis, Ilianna Vrouvaki, Panagiotis Siozos, Krystallia Melessanaki, Kostas Hatzigiannakis, Costas Fotakis, Giannis Zacharakis
A novel, non-invasive, imaging methodology, based on the photoacoustic effect, is introduced in the context of artwork diagnostics with emphasis on the uncovering of hidden features such as underdrawings or original sketch lines in paintings. Photoacoustic microscopy, a rapidly growing imaging method widely employed in biomedical research, exploits the ultrasonic acoustic waves, generated by light from a pulsed or intensity modulated source interacting with a medium, to map the spatial distribution of absorbing components...
April 7, 2017: Scientific Reports
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