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Low-intensity pulsed laser

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))...
September 13, 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 of Chinese population...
September 3, 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
G A Hine, A J Goers, L Feder, J A Elle, S J Yoon, H M Milchberg
We demonstrate the generation of axially modulated plasma waveguides using spatially patterned high-energy laser pulses. A spatial light modulator (SLM) imposes transverse phase front modulations on a low-energy (10 mJ) laser pulse which is interferometrically combined with a high-energy (130-450 mJ) pulse, sculpting its intensity profile. This enables dynamic and programmable shaping of the laser profile limited only by the resolution of the SLM and the intensity ratio of the two pulses. The plasma density profile formed by focusing the patterned pulse with an axicon lens is likewise dynamic and programmable...
August 1, 2016: Optics Letters
Andrey Yachmenev, Sergei N Yurchenko
A new scheme for enantiomer differentiation of chiral molecules using a pair of linearly polarized intense ultrashort laser pulses with skewed mutual polarization is presented. The technique relies on the fact that the off-diagonal anisotropic contributions to the electric polarizability tensor for two enantiomers have different signs. Exploiting this property, we are able to excite a coherent unidirectional rotation of two enantiomers with a π phase difference in the molecular electric dipole moment. The approach is robust and suitable for relatively high temperatures of molecular samples, making it applicable for selective chiral analysis of mixtures, and to chiral molecules with low barriers between enantiomers...
July 15, 2016: Physical Review Letters
X Ropagnol, M Khorasaninejad, M Raeiszadeh, S Safavi-Naeini, M Bouvier, C Y Côté, A Laramée, M Reid, M A Gauthier, T Ozaki
We report the generation of free space terahertz (THz) pulses with energy up to 8.3 ± 0.2 µJ from an encapsulated interdigitated ZnSe Large Aperture Photo-Conductive Antenna (LAPCA). An aperture of 12.2 cm<sup>2</sup> is illuminated using a 400 nm pump laser with multi-mJ energies at 10 Hz repetition rate. The calculated THz peak electric field is 331 ± 4 kV/cm with a spectrum characterized by a median frequency of 0.28 THz. Given its relatively low frequency, this THz field will accelerate charged particles efficiently having very large ponderomotive energy of 15 ± 1 eV for electrons in vacuum...
May 30, 2016: Optics Express
Yin-Wen Lee, Chien-Ming Chen, Chia-Wei Huang, Shih-Ken Chen, Jhang-Rong Jiang
We report on the demonstration of a passively Q-switched 1.55 µm fiber laser utilizing a colloidal PbS quantum dot (QD) thin film as a saturable absorber. Colloidal PbS QD films have several features that are advantageous in passively Q-switched fiber laser operation, including a large operation wavelength range, cost-effectiveness, and a low saturable absorption intensity. We conducted thorough material and optical studies to verify the advantages of PbS QDs in Q-switched laser operation and successfully generated 801 nJ pulses with a 24...
May 16, 2016: Optics Express
Chao Yan, Stefani Kocevska, Lev N Krasnoperov
Reaction of methyl peroxy radicals with hydroxyl radicals, CH3O2 + OH → CH3O + HO2 (1a) and CH3O2 + OH → CH2OO + H2O (1b) was studied using pulsed laser photolysis coupled to transient UV-vis absorption spectroscopy over the 292-526 K temperature range and pressure 1 bar (bath gas He). Hydroxyl radicals were generated in the reaction of electronically excited oxygen atoms O((1)D), produced in the photolysis of N2O at 193.3 nm, with H2O. Methyl peroxy radicals were generated in the reaction of methyl radicals, CH3, produced in the photolysis of acetone at 193...
August 11, 2016: Journal of Physical Chemistry. A
Edris Sarailou, Peter Delfyett
A linearized intensity modulator for periodic and pulsed light is proposed and demonstrated. The free carrier plasma effect has been used to modulate the refractive index of the phase section of a three-section mode-locked laser. If injection locked, the modulation induces an arcsine phase response on the three-section mode-locked laser. By introducing this mode-locked laser into a Mach-Zehnder interferometer biased at quadrature, one can realize a true linear intensity modulation. This novel laser suppresses any unwanted amplitude modulation and increases the performance of the linearized intensity modulator...
July 1, 2016: Optics Letters
Bo Young Park, Min Ki Hong, So Ra Kang, Seung Eun Hong
OBJECTIVE: Wound healing can be aided by the use of low- and medium-intensity lasers. The use of neodymium-yttrium-aluminum garnet (Nd: YAG) pulsed high-intensity laser therapy (HILT) with a 1064-nm wavelength laser provides deeper and more efficient penetration into tissue due to it being less absorbed by chromophores in tissue, e.g., hemoglobin, melanin and water, thereby enhancing the wound healing process. In this study, we examined the effect of high-intensity laser therapy on wound healing with a Q-switched Nd: YAG pulsed laser in an animal model...
June 28, 2016: Journal of Cosmetic and Laser Therapy: Official Publication of the European Society for Laser Dermatology
Yufei Jia, Ross A Kerner, Alex J Grede, Alyssa N Brigeman, Barry P Rand, Noel C Giebink
Organic-inorganic lead halide perovskite semiconductors have recently reignited the prospect of a tunable, solution-processed diode laser, which has the potential to impact a wide range of optoelectronic applications. Here, we demonstrate a metal-clad, second-order distributed feedback methylammonium lead iodide perovskite laser that marks a significant step toward this goal. Optically pumping this device with an InGaN diode laser at low temperature, we achieve lasing above a threshold pump intensity of 5 kW/cm(2) for durations up to ∼25 ns at repetition rates exceeding 2 MHz...
July 13, 2016: Nano Letters
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