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Intensed pulsed laser

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
Taiee Liang, Johannes M Bauer, James C Liu, Sayed H Rokni
A bremsstrahlung source term has been developed by the Radiation Protection (RP) group at SLAC National Accelerator Laboratory for high-intensity short-pulse laser-solid experiments between 10(17) and 10(22) W cm(-2) This source term couples the particle-in-cell plasma code EPOCH and the radiation transport code FLUKA to estimate the bremsstrahlung dose yield from laser-solid interactions. EPOCH characterizes the energy distribution, angular distribution, and laser-to-electron conversion efficiency of the hot electrons from laser-solid interactions, and FLUKA utilizes this hot electron source term to calculate a bremsstrahlung dose yield (mSv per J of laser energy on target)...
December 1, 2016: Radiation Protection Dosimetry
Bibilash Bs, Ravi Kumar Chittoria, Devinder Mohan Thappa, Devi Prasad Mohapatra, Friji M T, Dineshkumar S, Sandhya Pandey
BACKGROUND AND OBJECTIVES: There are no large volume comparative studies available to compare the efficacy of lasers over lights for hair removal in Fitzpatrick V and VI skin types. This study is designed to compare the efficacy of Nd:YAG Laser versus IPL in the darker skin types. STUDY DESIGN/MATERIALS AND METHODS: Thirty nine patients included in Group-1 were treated with Nd:YAG and 31 in group-2 with IPL. Both groups received 5 sessions of treatment. The hair counts were assessed using digital photography and manual counting method before and after treatment and results were analysed...
December 2, 2016: Journal of Cosmetic and Laser Therapy: Official Publication of the European Society for Laser Dermatology
C R Stillman, P M Nilson, S T Ivancic, C Mileham, I A Begishev, R K Junquist, D J Nelson, D H Froula
A picosecond, time-resolved, x-ray spectroscopy platform was developed to study the thermal line emission from rapidly heated solid targets containing buried aluminum or iron layers. The targets were driven by high-contrast 1ω or 2ω laser pulses at focused intensities up to 1 × 10(19) W/cm(2). The experimental platform combines time-integrating and time-resolved x-ray spectrometers. Picosecond time resolution was achieved with a pair of ultrafast x-ray streak cameras coupled to high-throughput Hall spectrometers...
November 2016: Review of Scientific Instruments
P M Nilson, F Ehrne, C Mileham, D Mastrosimone, R K Jungquist, C Taylor, C R Stillman, S T Ivancic, R Boni, J Hassett, D J Lonobile, R W Kidder, M J Shoup, A A Solodov, C Stoeckl, W Theobald, D H Froula, K W Hill, L Gao, M Bitter, P Efthimion, D D Meyerhofer
A high-resolving-power x-ray spectrometer has been developed for the OMEGA EP Laser System based on a spherically bent Si [220] crystal with a radius of curvature of 330 mm and a Spectral Instruments (SI) 800 Series charge-coupled device. The instrument measures time-integrated x-ray emission spectra in the 7.97- to 8.11-keV range, centered on the Cu Kα1 line. To demonstrate the performance of the spectrometer under high-power conditions, Kα1,2 emission spectra were measured from Cu foils irradiated by the OMEGA EP laser with 100-J, 1-ps pulses at focused intensities above 10(18) W/cm(2)...
November 2016: Review of Scientific Instruments
A Imburgia, P Romano, M Caruso, F Viola, R Miceli, E Riva Sanseverino, A Madonia, G Schettino
The space charge accumulation phenomenon has garnered great interest over the last two decades because of the increased use of direct current in high voltage electrical systems. In this context, a significant relevance has been achieved by the thermal methods, used for solid dielectrics. This paper presents a review of this non-destructive measurement system used for the measurement of space charge. The thermal pulse method, the thermal step method, and the laser intensity modulation method are described. For each configuration, the principle of operation, the thicknesses analyzed, and the spatial resolution are described, reporting also the main related applications...
November 2016: Review of Scientific Instruments
M Z Mo, X Shen, Z Chen, R K Li, M Dunning, K Sokolowski-Tinten, Q Zheng, S P Weathersby, A H Reid, R Coffee, I Makasyuk, S Edstrom, D McCormick, K Jobe, C Hast, S H Glenzer, X Wang
We have developed a single-shot mega-electronvolt ultrafast-electron-diffraction system to measure the structural dynamics of warm dense matter. The electron probe in this system is featured by a kinetic energy of 3.2 MeV and a total charge of 20 fC, with the FWHM pulse duration and spot size at sample of 350 fs and 120 μm respectively. We demonstrate its unique capability by visualizing the atomic structural changes of warm dense gold formed from a laser-excited 35-nm freestanding single-crystal gold foil...
November 2016: Review of Scientific Instruments
Z Chen, P Hering, S B Brown, C Curry, Y Y Tsui, S H Glenzer
To study the rapid evolution of AC conductivity from ultrafast laser excited warm dense matter (WDM), a spatial chirp single-shot method is developed utilizing a crossing angle pump-probe configuration. The pump beam is shaped individually in two spatial dimensions so that it can provide both sufficient laser intensity to excite the material to warm dense matter state and a uniform time window of up to 1 ps with sub-100 fs FWHM temporal resolution. Temporal evolution of AC conductivity in laser excited warm dense gold was also measured...
November 2016: Review of Scientific Instruments
M Gauthier, J B Kim, C B Curry, B Aurand, E J Gamboa, S Göde, C Goyon, A Hazi, S Kerr, A Pak, A Propp, B Ramakrishna, J Ruby, O Willi, G J Williams, C Rödel, S H Glenzer
We report on the successful operation of a newly developed cryogenic jet target at high intensity laser-irradiation. Using the frequency-doubled Titan short pulse laser system at Jupiter Laser Facility, Lawrence Livermore National Laboratory, we demonstrate the generation of a pure proton beam a with maximum energy of 2 MeV. Furthermore, we record a quasi-monoenergetic peak at 1.1 MeV in the proton spectrum emitted in the laser forward direction suggesting an alternative acceleration mechanism. Using a solid-density mixed hydrogen-deuterium target, we are also able to produce pure proton-deuteron ion beams...
November 2016: Review of Scientific Instruments
A M Rasmus, A U Hazi, M J-E Manuel, C C Kuranz, S R Klein, P X Belancourt, J R Fein, M J MacDonald, R P Drake, B B Pollock, J Park, G J Williams, H Chen
Ultra-intense short pulse lasers incident on solid targets (e.g., thin Au foils) produce well collimated, broad-spectrum proton beams. These proton beams can be used to characterize magnetic fields, electric fields, and density gradients in high energy-density systems. The LLNL-Imaging Proton Spectrometer (L-IPS) was designed and built [H. Chen et al., Rev. Sci. Instrum. 81, 10D314 (2010)] for use with such laser produced proton beams. The L-IPS has an energy range of 50 keV-40 MeV with a resolving power (E/dE) of about 275 at 1 MeV and 21 at 20 MeV, as well as a single spatial imaging axis...
November 2016: Review of Scientific Instruments
J B Kim, S Göde, S H Glenzer
The advent of high-intensity, high-repetition-rate lasers has led to the need for replenishing targets of interest for high energy density sciences. We describe the design and characterization of a cryogenic microjet source, which can deliver a continuous stream of liquid hydrogen with a diameter of a few microns. The jet has been imaged at 1 μm resolution by shadowgraphy with a short pulse laser. The pointing stability has been measured at well below a mrad, for a stable free-standing filament of solid-density hydrogen...
November 2016: Review of Scientific Instruments
Yu Xia, Zhibing Li
To understand laser-assisted field evaporation of semiconductors and insulators at the microscopic level, we study the time evolution of the electronic and atomic structure of a MgO cluster in high electrostatic fields subjected to strong laser pulses. We find that the critical laser intensity for evaporation decreases linearly as the electrostatic field strength increases. The optical absorption enhancement in high electrostatic field is confirmed by the redshift of the optical absorption spectra, the reduction of the energy gap, and the increase of the absorption cross section...
November 28, 2016: Journal of Chemical Physics
S Ter-Avetisyan, A Andreev, K Platonov, J H Sung, S K Lee, H W Lee, J Y Yoo, P K Singh, H Ahmed, C Scullion, K F Kakolee, T W Jeong, P Hadjisolomou, M Borghesi
A significant level of back reflected laser energy was measured during the interaction of ultra-short, high contrast PW laser pulses with solid targets at 30° incidence. 2D PIC simulations carried out for the experimental conditions show that at the laser-target interface a dynamic regular structure is generated during the interaction, which acts as a grating (quasi-grating) and reflects back a significant amount of incident laser energy. With increasing laser intensity above 10<sup>18</sup> W/cm<sup>2</sup> the back reflected fraction increases due to the growth of the surface modulation to larger amplitudes...
November 28, 2016: Optics Express
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
Jingdong Zhang, Tao Zhu, Huan Zhou, Shihong Huang, Min Liu, Wei Huang
We demonstrate a cost-effective distributed fiber sensing system for the multi-parameter detection of the vibration, the temperature, and the strain by integrating phase-sensitive optical time domain reflectometry (φ-OTDR) and Brillouin optical time domain reflectometry (B-OTDR). Taking advantage of the fast changing property of the vibration and the static properties of the temperature and the strain, both the width and intensity of the laser pulses are modulated and injected into the single-mode sensing fiber proportionally, so that three concerned parameters can be extracted simultaneously by only one photo-detector and one data acquisition channel...
November 28, 2016: Optics Express
Christian L Goueguel, Dustin L McIntyre, Jinesh C Jain
Optical emission spectroscopic studies have been carried out to investigate the pressure effect of CO<sub>2</sub> on laser-produced underwater plasma. The plasma was generated by focusing 1064 nm, 6 ns pulses from a Nd:YAG laser in a CO<sub>2</sub>-bearing solution. The temporal evolution of the continuum emission, Sr and Ba lines, and plasma electron density and temperature was characterized under CO<sub>2</sub> pressure ranging from 10 to 300 bars. The electron density measurements were made using the Stark broadening of the 455...
December 1, 2016: Optics Letters
David Gauthier, Enrico Allaria, Marcello Coreno, Ivan Cudin, Hugo Dacasa, Miltcho Boyanov Danailov, Alexander Demidovich, Simone Di Mitri, Bruno Diviacco, Eugenio Ferrari, Paola Finetti, Fabio Frassetto, David Garzella, Swen Künzel, Vincent Leroux, Benoît Mahieu, Nicola Mahne, Michael Meyer, Tommaso Mazza, Paolo Miotti, Giuseppe Penco, Lorenzo Raimondi, Primož Rebernik Ribič, Robert Richter, Eléonore Roussel, Sebastian Schulz, Luca Sturari, Cristian Svetina, Mauro Trovò, Paul Andreas Walker, Marco Zangrando, Carlo Callegari, Marta Fajardo, Luca Poletto, Philippe Zeitoun, Luca Giannessi, Giovanni De Ninno
Chirped pulse amplification in optical lasers is a revolutionary technique, which allows the generation of extremely powerful femtosecond pulses in the infrared and visible spectral ranges. Such pulses are nowadays an indispensable tool for a myriad of applications, both in fundamental and applied research. In recent years, a strong need emerged for light sources producing ultra-short and intense laser-like X-ray pulses, to be used for experiments in a variety of disciplines, ranging from physics and chemistry to biology and material sciences...
December 1, 2016: Nature Communications
Jun Liu, Lan Jin, Zhongtao Zhang
BACKGROUND AND OBJECTIVES: Laparoscopic transcystic common bile duct exploration (LTCBDE) is a complex procedure requiring expertise in laparoscopic and choledochoscopic skills. The purpose of this study was to investigate the safety and feasibility of treating biliary calculi through laparoscopic transcystic exploration of the CBD via an ultrathin choledochoscope combined with dual-frequency laser lithotripsy. METHODS: From August 2011 through September 2014, 89 patients at our hospital were treated for cholecystolithiasis with biliary calculi...
October 2016: JSLS: Journal of the Society of Laparoendoscopic Surgeons
Hwa Jung Ryu, Ji Min Lee, Hee Won Jang, Hae Chul Park, Im Joo Rhyu, Il-Hwan Kim
BACKGROUND: Recently, the pulse-in-pulse mode of intense pulsed light (IPL) has been used increasingly for the treatment of melasma. OBJECTIVE: To observe the morphologic changes in the melanophore in adult zebrafish after irradiation with conventional and pulse-in-pulse IPL and Q-switched Nd:YAG (QSNY) laser. METHODS: Adult zebrafish were irradiated with conventional and pulse-in-pulse mode of IPL. The conditions for conventional IPL were 3 mJ/cm(2), 560 nm filter, and pulse widths of 7, 20, and 35 msec...
December 2016: Annals of Dermatology
Robin F Castelino, Michael Hynes, Chelsea E Munding, Sergey Telenkov, F Stuart Foster
Intravascular photoacoustic (IVPA) imaging has the potential to characterize lipid-rich structures based on the optical absorption contrast of tissues. In this study, we explore frequency domain photoacoustics (FDPA) for intravascular applications. The system employed an intensity-modulated continuous wave (CW) laser diode, delivering 1W over an intensity modulated chirp frequency of 4-12MHz. We demonstrated the feasibility of this approach on an agar vessel phantom with graphite and lipid targets, imaged using a planar acoustic transducer co-aligned with an optical fibre, allowing for the co-registration of IVUS and FDPA images...
November 1, 2016: Biomedical Optics Express
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