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Low-intensity pulsed laser

Cheng Jin, Kyung-Han Hong, C D Lin
We numerically demonstrate the generation of intense, low-divergence soft X-ray isolated attosecond pulses in a gas-filled hollow waveguide using synthesized few-cycle two-color laser waveforms. The waveform is a superposition of a fundamental and its second harmonic optimized such that highest harmonic yields are emitted from each atom. We then optimize the gas pressure and the length and radius of the waveguide such that bright coherent high-order harmonics with angular divergence smaller than 1 mrad are generated, for photon energy from the extreme ultraviolet to soft X-rays...
December 8, 2016: Scientific Reports
Janet Y Li, Elizabeth Rc Geddes, Deanne M Robinson, Paul M Friedman
Melasma is a pigmentary disorder of unclear etiology with numerous treatment options and high recurrence rates. Laser and light therapies may be utilized cautiously as second- or third-line options for recalcitrant melasma, but low-energy settings are preferred due to the risk of postinflammatory hyperpigmentation and melasma stimulation. Commonly used lasers include the low-fluence 1064-nm Q-switched neodymium-doped yttrium aluminum garnet laser, nonablative fractionated lasers, and intense pulsed light. Strict sun protection, concomitant use of bleaching agents, and maintenance treatments are necessary...
December 2016: Seminars in Cutaneous Medicine and Surgery
Zi-Yu Liu, Yi-Hsin Chen, Yen-Chun Chen, Hsiang-Yu Lo, Pin-Ju Tsai, Ite A Yu, Ying-Cheng Chen, Yong-Fan Chen
We demonstrate an efficient cross-phase modulation (XPM) based on a closed-loop double-Λ system. The property of the double-Λ medium can be controlled by changing the phases of the applied optical fields. This phase-dependent XPM scheme can achieve large phase modulations at low-light intensities without requiring cavities or tightly focusing laser beams. With this scheme, we observe a π-level phase shift with two pulses, both consisting of eight photons in cold rubidium atoms. Such a novel scheme provides a simple route to generate strong interactions between photons and may have potential applications in all-optical quantum signal processing...
November 11, 2016: Physical Review Letters
Wonsuk Lee, Qiushu Chen, Xudong Fan, Dong Ki Yoon
DNA lasers self-amplify optical signals from a DNA analyte as well as thermodynamic differences between sequences, allowing quasi-digital DNA detection. However, these systems have drawbacks, such as relatively large sample consumption and complicated dye labelling. Moreover, although the lasing signal can detect the target DNA, it is superimposed on an unintended fluorescence background, which persists for non-target DNA samples as well. From an optical point of view, it is thus not truly digital detection and requires spectral analysis to identify the target...
November 29, 2016: Lab on a Chip
J Adamonis, A Aleknavičius, K Michailovas, S Balickas, V Petrauskienė, T Gertus, A Michailovas
We present implementation of the energy-efficient and flexible laser beam shaping technique in a high-power and high-energy laser amplifier system. The beam shaping is based on a spatially variable wave plate (SVWP) fabricated by femtosecond laser nanostructuring of glass. We reshaped the initially Gaussian beam into a super-Gaussian (SG) of the 12th order with efficiency of about 50%. The 12th order of the SG beam provided the best compromise between large fill factor, low diffraction on the edges of the active media, and moderate intensity distribution modification during free-space propagation...
October 1, 2016: Applied Optics
A J H van der Torren, S J van der Molen, J Aarts
By combining low-energy electron microscopy with in situ pulsed laser deposition we have developed a new technique for film growth analysis, making use of both diffraction and real-space information. Working at the growth temperature, we can use: the intensity and profile variations of the specular beam to follow the coverage in a layer-by-layer fashion; real-space microscopy to follow e.g. atomic steps at the surface; and electron reflectivity to probe the unoccupied band structure of the grown material. Here, we demonstrate our methodology for homo-epitaxial growth of SrTiO3...
November 9, 2016: Nanotechnology
Tobias Steinle, Florian Mörz, Andy Steinmann, Harald Giessen
A highly stable 350 fs laser system with a gap-free tunability from 1.33 to 2.0 μm and 2.13 to 20 μm is demonstrated. Nanojoule-level pulse energy is achieved in the mid-infrared at a 43 MHz repetition rate. The system utilizes a post-amplified fiber-feedback optical parametric oscillator followed by difference frequency generation between the signal and idler. No locking or synchronization electronics are required to achieve outstanding free-running output power and spectral stability of the whole system...
November 1, 2016: Optics Letters
D Komar, K-H Meiwes-Broer, J Tiggesbäumker
We report on a versatile ion analyzer which is capable to resolve ion charge states and energies with a resolution of E/ΔE = 100 at 75 keV/nucleon. Charge states are identified by their characteristic deflection in a magnetic field, whereas the ion energies are independently determined by a time-of-flight measurement. To monitor the signals a delay-line detector is used which records ion impact positions and times in each laser shot. Compared to conventional Thomson parabola spectrometers our instrument provides a low background measurement, hence a superior dynamic range...
October 2016: Review of Scientific Instruments
M Pang, W He, P St J Russell
We report a Tm-doped soliton fiber laser passively mode-locked by intense optoacoustic interactions in a short length of solid-core silica photonic crystal fiber (PCF) with a nanobore in core-center. A repetition rate of 1.446 GHz pulse is achieved, corresponding to the 52nd harmonic of the 27.8 MHz cavity round-trip frequency. Strong optoacoustic interactions in this PCF-based, Tm-doped fiber laser ensure stable and repeatable gigahertz-rate pulse train generation at 1.85 μm wavelength, with a high supermode noise suppression ratio and low pulse timing jitter...
October 1, 2016: Optics Letters
Yechiel Frank, Arie Zigler, Zohar Henis
The atomic kinetics of solid density low-Z material under an intense oscillating laser field is presented. The transient behavior of the average ionization and the heating mechanism is analyzed. Temporal oscillations in excited configurations populations caused by the laser field oscillations are demonstrated. These phenomena present a method for creating short, 1-100 fs, monochromatic but incoherent x-ray pulses and for measuring basic atomic rates.
September 2016: Physical Review. E
Adam Michael Scheer, Arkke J Eskola, David L Osborn, Leonid Sheps, Craig Allen Taatjes
The pulsed photolytic chlorine-initiated oxidation of diethyl ketone [DEK; (CH3CH2)2C=O], 2,2,4,4-d4-DEK [d4-DEK; (CH3CD2)2C=O] and 1,1,1,5,5,5-d6-DEK [d6-DEK; (CD3CH2)2C=O] is studied at 8 Torr and 1 - 2 atm and from 400 - 625 K. Cl atoms produced by laser photolysis react with diethyl ketone to form either primary (3-pentan-on-1-yl, RP) or secondary (3-pentan-on-2-yl, RS¬¬) radicals, which in turn react with O2. Multiplexed time of flight mass spectrometry, coupled to either a hydrogen discharge lamp or tunable synchrotron photoionizing radiation, is used to detect products as a function of mass, time and photon energy...
October 11, 2016: Journal of Physical Chemistry. A
Hirobumi Mineo, Masahiro Yamaki, Gap-Sue Kim, Yoshiaki Teranishi, Sheng Hsien Lin, Yuichi Fujimura
A new laser-control scenario of unidirectional π-electron rotations in a low-symmetry aromatic ring molecule having no degenerate excited states is proposed. This scenario is based on dynamic Stark shifts of two relevant excited states using two linearly polarized stationary lasers. Each laser is set to selectively interact with one of the two electronic states, the lower and higher excited states are shifted up and down with the same rate, respectively, and the two excited states become degenerate at their midpoint...
September 29, 2016: Physical Chemistry Chemical Physics: PCCP
Jelena Barbaric, Rachel Abbott, Pawel Posadzki, Mate Car, Laura H Gunn, Alison M Layton, Azeem Majeed, Josip Car
BACKGROUND: Acne vulgaris is a very common skin problem that presents with blackheads, whiteheads, and inflamed spots. It frequently results in physical scarring and may cause psychological distress. The use of oral and topical treatments can be limited in some people due to ineffectiveness, inconvenience, poor tolerability or side-effects. Some studies have suggested promising results for light therapies. OBJECTIVES: To explore the effects of light treatment of different wavelengths for acne...
September 27, 2016: Cochrane Database of Systematic Reviews
Elena A Anashkina, Vladislav N Ginzburg, Anton A Kochetkov, Ivan V Yakovlev, Arkady V Kim, Efim A Khazanov
We report a method for ultrashort pulse reconstruction based only on the pulse spectrum and two self-phase modulated (SPM) spectra measured after pulse propagation through thin media with a Kerr nonlinearity. The advantage of this method is that it is a simple and very effective tool for characterization of complex signals. We have developed a new retrieval algorithm that was verified by reconstructing numerically generated fields, such as a complex electric field of double pulses and few-cycle pulses with noises, pedestals and dips down to zero spectral intensity, which is challenging for commonly used techniques...
2016: Scientific Reports
Brian Abbey, Ruben A Dilanian, Connie Darmanin, Rebecca A Ryan, Corey T Putkunz, Andrew V Martin, David Wood, Victor Streltsov, Michael W M Jones, Naylyn Gaffney, Felix Hofmann, Garth J Williams, Sébastien Boutet, Marc Messerschmidt, M Marvin Seibert, Sophie Williams, Evan Curwood, Eugeniu Balaur, Andrew G Peele, Keith A Nugent, Harry M Quiney
X-ray free-electron lasers (XFELs) deliver x-ray pulses with a coherent flux that is approximately eight orders of magnitude greater than that available from a modern third-generation synchrotron source. The power density of an XFEL pulse may be so high that it can modify the electronic properties of a sample on a femtosecond time scale. Exploration of the interaction of intense coherent x-ray pulses and matter is both of intrinsic scientific interest and of critical importance to the interpretation of experiments that probe the structures of materials using high-brightness femtosecond XFEL pulses...
September 2016: Science Advances
Paulo Roberto Vicente de Paiva, Shaiane Silva Tomazoni, Douglas Scott Johnson, Adriane Aver Vanin, Gianna Móes Albuquerque-Pontes, Caroline Dos Santos Monteiro Machado, Heliodora Leão Casalechi, Paulo de Tarso Camillo de Carvalho, Ernesto Cesar Pinto Leal-Junior
Cryotherapy for post-exercise recovery remains widely used despite the lack of quality evidence. Photobiomodulation therapy (PBMT) studies (with both low-level laser therapy and light-emitting diode therapy) have demonstrated positive scientific evidence to suggest its use. The study aims to evaluate PBMT and cryotherapy as a single or combined treatment on skeletal muscle recovery after eccentric contractions of knee extensors. Fifty healthy male volunteers were recruited and randomized into five groups (PBMT, cryotherapy, cryotherapy + PBMT, PMBT + cryotherapy, or placebo) for a randomized, double-blinded, placebo-controlled trial that evaluated exercise performance (maximum voluntary contraction (MVC)), delayed onset muscle soreness (DOMS), and muscle damage (creatine kinase (CK))...
December 2016: Lasers in Medical Science
La-Ga Tong, Yan Wu, Bin Wang, Xue-Gang Xu, Han-Deng Tu, Hong-Duo Chen, Yuan-Hong Li
BACKGROUND: Melasma is the most common and distressing pigmentary disorder presenting to dermatology clinics. Various treatment protocols for melasma have been suggested in the previous literature and applied in various clinical settings. However, no satisfactory therapy has been widely accepted. OBJECTIVE: To evaluate the efficiency and safety of a combination treatment with fractional Q-switched ruby laser (QSRL) and intense pulsed light (IPL) for melasma in Chinese population...
November 18, 2016: Journal of Cosmetic and Laser Therapy: Official Publication of the European Society for Laser Dermatology
Jae-Jun Choi, Soo-Jin Choi, Jack J Yoh
Categorized certified reference materials simulating metal, rock, soils, or dusts are used to demonstrate the standoff detection capability of laser-induced breakdown spectroscopy (LIBS) at severely low pressure conditions. A Q-switched Nd:YAG laser operating at 1064 nm with 17.2-50 mJ energy per pulse was used to obtain sample signals from a distance of 5.5 m; the detection sensitivity at pressures down to 0.01 torr was also analyzed. The signal intensity response to pressure changes is explained by the ionization energy and electronegativity of elements, and from the estimated full width half-maximum (FWHM) and electron density, the decrease in both background noise and line broadening makes it suitable for low pressure detection using the current standoff LIBS configuration...
September 2016: Applied Spectroscopy
P L Poole, A Krygier, G E Cochran, P S Foster, G G Scott, L A Wilson, J Bailey, N Bourgeois, C Hernandez-Gomez, D Neely, P P Rajeev, R R Freeman, D W Schumacher
We describe the first demonstration of plasma mirrors made using freely suspended, ultra-thin films formed dynamically and in-situ. We also present novel particle-in-cell simulations that for the first time incorporate multiphoton ionization and dielectric models that are necessary for describing plasma mirrors. Dielectric plasma mirrors are a crucial component for high intensity laser applications such as ion acceleration and solid target high harmonic generation because they greatly improve pulse contrast...
2016: Scientific Reports
Max F Hantke, Dirk Hasse, Tomas Ekeberg, Katja John, Martin Svenda, Duane Loh, Andrew V Martin, Nicusor Timneanu, Daniel S D Larsson, Gijs van der Schot, Gunilla H Carlsson, Margareta Ingelman, Jakob Andreasson, Daniel Westphal, Bianca Iwan, Charlotte Uetrecht, Johan Bielecki, Mengning Liang, Francesco Stellato, Daniel P DePonte, Sadia Bari, Robert Hartmann, Nils Kimmel, Richard A Kirian, M Marvin Seibert, Kerstin Mühlig, Sebastian Schorb, Ken Ferguson, Christoph Bostedt, Sebastian Carron, John D Bozek, Daniel Rolles, Artem Rudenko, Lutz Foucar, Sascha W Epp, Henry N Chapman, Anton Barty, Inger Andersson, Janos Hajdu, Filipe R N C Maia
Ultra-intense femtosecond X-ray pulses from X-ray lasers permit structural studies on single particles and biomolecules without crystals. We present a large data set on inherently heterogeneous, polyhedral carboxysome particles. Carboxysomes are cell organelles that vary in size and facilitate up to 40% of Earth's carbon fixation by cyanobacteria and certain proteobacteria. Variation in size hinders crystallization. Carboxysomes appear icosahedral in the electron microscope. A protein shell encapsulates a large number of Rubisco molecules in paracrystalline arrays inside the organelle...
2016: Scientific Data
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