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Intense pulsed light

Marc W Guetg, Alberto A Lutman, Yuantao Ding, Timothy J Maxwell, Franz-Josef Decker, Uwe Bergmann, Zhirong Huang
X-ray free-electron lasers combine a high pulse power, short pulse length, narrow bandwidth, and high degree of transverse coherence. Any increase in the photon pulse power, while shortening the pulse length, will further push the frontier on several key x-ray free-electron laser applications including single-molecule imaging and novel nonlinear x-ray methods. This Letter shows experimental results at the Linac Coherent Light Source raising its maximum power to more than 300% of the current limit while reducing the photon pulse length to 10 fs...
January 5, 2018: Physical Review Letters
Cristian Bonatto, Antonio Endler
We investigate the occurrence of extreme and rare events, i.e., giant and rare light pulses, in a periodically modulated CO_{2} laser model. Due to nonlinear resonant processes, we show a scenario of interaction between chaotic bands of different orders, which may lead to the formation of extreme and rare events. We identify a crisis line in the modulation parameter space, and we show that, when the modulation amplitude increases, remaining in the vicinity of the crisis, some statistical properties of the laser pulses, such as the average and dispersion of amplitudes, do not change much, whereas the amplitude of extreme events grows enormously, giving rise to extreme events with much larger deviations than usually reported, with a significant probability of occurrence, i...
July 2017: Physical Review. E
A Grassi, M Grech, F Amiranoff, A Macchi, C Riconda
The Weibel instability from counterstreaming plasma flows is a basic process highly relevant for collisionless shock formation in astrophysics. In this paper we investigate, via two- and three-dimensional simulations, suitable configurations for laboratory investigations of the ion Weibel instability (IWI) driven by a fast quasineutral plasma flow launched into the target via the radiation pressure of an ultra-high-intensity laser pulse ("hole-boring" process). The use of S-polarized light at oblique incidence is found to be an optimal configuration for driving IWI, as it prevents the development of surface rippling observed at normal incidence that would lead to strong electron heating and would favor competing instabilities...
September 2017: Physical Review. E
Sebastian Maehrlein, Alexander Paarmann, Martin Wolf, Tobias Kampfrath
In stimulated Raman scattering, two incident optical waves induce a force oscillating at the difference of the two light frequencies. This process has enabled important applications such as the excitation and coherent control of phonons and magnons by femtosecond laser pulses. Here, we experimentally and theoretically demonstrate the so far neglected up-conversion counterpart of this process: THz sum-frequency excitation of a Raman-active phonon mode, which is tantamount to two-photon absorption by an optical transition between two adjacent vibrational levels...
September 22, 2017: Physical Review Letters
Luciana L Faucz, Sonia E Will, Consuelo J Rodrigues, Henrique Hesse, Angelina C Moraes, Durvanei A Maria
BACKGROUND AND OBJECTIVE: The aging of human skin includes intrinsic aging and photo-aging, which are characterized by a decrease in collagen and the deposition of abnormal elastic fibers. Intense pulsed light (IPL) sources are widely used in medicine to treat various cosmetic problems, including photo-damaged skin. Few studies have examined the microscopic changes produced by IPL. The objective of this study was to quantitatively evaluate the effects of IPL on collagen and elastic fibers in mice...
January 16, 2018: Lasers in Surgery and Medicine
Michael Schneider, Christian M Günther, Bastian Pfau, Flavio Capotondi, Michele Manfredda, Marco Zangrando, Nicola Mahne, Lorenzo Raimondi, Emanuele Pedersoli, Denys Naumenko, Stefan Eisebitt
Free-electron lasers (FELs) in the extreme ultraviolet (XUV) and X-ray regime opened up the possibility for experiments at high power densities, in particular allowing for fluence-dependent absorption and scattering experiments to reveal non-linear light-matter interactions at ever shorter wavelengths. Findings of such non-linear effects are met with tremendous interest, but prove difficult to understand and model due to the inherent shot-to-shot fluctuations in photon intensity and the often structured, non-Gaussian spatial intensity profile of a focused FEL beam...
January 15, 2018: Nature Communications
M S Krivokorytov, Q Zeng, B V Lakatosh, A Yu Vinokhodov, Yu V Sidelnikov, V O Kompanets, V M Krivtsun, K N Koshelev, C D Ohl, V V Medvedev
Targeting micrometer sized metal droplets with near-infrared sub-picosecond laser pulses generates intense stress-confined acoustic waves within the droplet. Spherical focusing amplifies their pressures. The rarefaction wave nucleates cavitation at the center of the droplet, which explosively expands with a repeatable fragmentation scenario resulting into high-speed jetting. We predict the number of jets as a function of the laser energy by coupling the cavitation bubble dynamics with Rayleigh-Taylor instabilities...
January 12, 2018: Scientific Reports
Sreekanth Perumbilavil, Alberto López-Ortega, Gaurav Kumar Tiwari, Josep Nogués, Tamio Endo, Reji Philip
Nonlinear optical nanostructured materials are gaining increased interest as optical limiters for various applications, although many of them suffer from reduced efficiencies at high-light fluences due to photoinduced deterioration. The nonlinear optical properties of ferrite core/shell nanoparticles showing their robustness for ultrafast optical limiting applications are reported. At 100 fs ultrashort laser pulses the effective two-photon absorption (2PA) coefficient shows a nonmonotonic dependence on the shell thickness, with a maximum value obtained for thin shells...
January 11, 2018: Small
Peter Hamm, Markus Meuwly, Steve L Johnson, Paul Beaud, Urs Staub
Recent years have seen dramatic developments in the technology of intense pulsed light sources in the THz frequency range. Since many dipole-active excitations in solids and molecules also lie in this range, there is now a tremendous potential to use these light sources to study linear and nonlinear dynamics in such systems. While several experimental investigations of THz-driven dynamics in solid-state systems have demonstrated a variety of interesting linear and nonlinear phenomena, comparatively few efforts have been made to drive analogous dynamics in molecular systems...
November 2017: Structural Dynamics (Melville, N.Y.)
S L Johnson, M Savoini, P Beaud, G Ingold, U Staub, F Carbone, L Castiglioni, M Hengsberger, J Osterwalder
We present a non-comprehensive review of some representative experimental studies in crystalline condensed matter systems where the effects of intense ultrashort light pulses are probed using x-ray diffraction and photoelectron spectroscopy. On an ultrafast (sub-picosecond) time scale, conventional concepts derived from the assumption of thermodynamic equilibrium must often be modified in order to adequately describe the time-dependent changes in material properties. There are several commonly adopted approaches to this modification, appropriate in different experimental circumstances...
November 2017: Structural Dynamics (Melville, N.Y.)
R J Squibb, M Sapunar, A Ponzi, R Richter, A Kivimäki, O Plekan, P Finetti, N Sisourat, V Zhaunerchyk, T Marchenko, L Journel, R Guillemin, R Cucini, M Coreno, C Grazioli, M Di Fraia, C Callegari, K C Prince, P Decleva, M Simon, J H D Eland, N Došlić, R Feifel, M N Piancastelli
The first steps in photochemical processes, such as photosynthesis or animal vision, involve changes in electronic and geometric structure on extremely short time scales. Time-resolved photoelectron spectroscopy is a natural way to measure such changes, but has been hindered hitherto by limitations of available pulsed light sources in the vacuum-ultraviolet and soft X-ray spectral region, which have insufficient resolution in time and energy simultaneously. The unique combination of intensity, energy resolution, and femtosecond pulse duration of the FERMI-seeded free-electron laser can now provide exceptionally detailed information on photoexcitation-deexcitation and fragmentation in pump-probe experiments on the 50-femtosecond time scale...
January 4, 2018: Nature Communications
Rhys Wyber, Barry Osmond, Michael B Ashcroft, Zbynek Malenovský, Sharon A Robinson
Understanding the net photosynthesis of plant canopies requires quantifying photosynthesis in challenging environments, principally due to the variable light intensities and qualities generated by sunlight interactions with clouds and surrounding foliage. The dynamics of sunflecks and rates of change in light intensity at the beginning and end of sustained light (SL) events makes photosynthetic measurements difficult, especially when dealing with less accessible parts of plant foliage. High time resolved photosynthetic monitoring from pulse amplitude modulated (PAM) fluorometers has limited applicability due to the invasive nature of frequently applied saturating flashes...
December 28, 2017: Tree Physiology
G Sanclemente, V Ruiz-Cañas, J M Miranda, A P Ferrín, P A Ramirez, G N Hernandez
INTRODUCTION: Photodynamic therapy (PDT) involves the combination of a light source and a photosensitizing agent to induce tissue damage via the generation of singlet oxygen. Although topical PDT has been approved for other indications, its use in facial photodamage is uncertain. AIMS: To assess the efficacy and safety of PDT in facial skin photoaging. METHODS: All randomized clinical trials (RCTs) evaluating the efficacy and safety of any form of topical PDT for the treatment of facial photodamage (dermatoheliosis) or photoaging in patients older than 18 years, were included...
December 30, 2017: Actas Dermo-sifiliográficas
Nafila Shakeeb, Sahibzada Mahmood Noor, Ghafoor Ullah, Mohammand Majid Paracha
OBJECTIVE: To compare the efficacy of intense pulse light therapy (IPL) and triple combination cream (TCC) versus intense pulse light therapy and triple combination cream alone in epidermal melasma treatment, downgrading MASI score to more than 10. STUDY DESIGN: Randomized controlled trial. PLACE AND DURATION OF STUDY: Dermatology Department, Lady Reading Hospital, Peshawar, from August 2014 to January 2015. METHODOLOGY: Patients of 18-45 years were included in the study with Fitzpatrick skin type II-V...
January 2018: Journal of the College of Physicians and Surgeons—Pakistan: JCPSP
Xinhua Xie, Tian Wang, ShaoGang Yu, XuanYang Lai, Stefan Roither, Daniil Kartashov, Andrius Baltuška, XiaoJun Liu, André Staudte, Markus Kitzler
We use orthogonally polarized two-color (OTC) laser pulses to separate quantum paths in the multiphoton ionization of Ar atoms. Our OTC pulses consist of 400 and 800 nm light at a relative intensity ratio of 10∶1. We find a hitherto unobserved interference in the photoelectron momentum distribution, which exhibits a strong dependence on the relative phase of the OTC pulse. Analysis of model calculations reveals that the interference is caused by quantum pathways from nonadjacent quarter cycles.
December 15, 2017: Physical Review Letters
Wenjia Sun, Jiaqiang Wu, Hui Qian, Juemin Zhao, Leihong Xiang, Chengfeng Zhang
This study aimed to evaluate the effect of IPL treatment on Asian skin by reflectance confocal microscopy (RCM) analysis. Ten Asian female volunteers (39~54 years old, Fitzpatrick skin type III~IV) received five monthly IPL treatments. RCM skin images were evaluated, and several skin physiological parameters including thickness of stratum corneum, minimal thickness of epidermis, thickness of basal layer, density of dermal papillae, and mean diameter of papillae capillaries were measured both at baseline and 1 month after the last treatment...
December 18, 2017: Lasers in Medical Science
Andong Wang, Lan Jiang, Xiaowei Li, Zhijie Xu, Lingling Huang, Kaihu Zhang, Xu Ji, Yongfeng Lu
In this paper, we investigated the material redistribution phenomenon controlled by spatially modulated femtosecond laser pulses on a silicon surface. The intensity distribution was shaped by using a spatial light modulator. The material was first selectively melted and then redistributed by the laser-induced plasma. Thus, complex surface patterns were formed conformal to the laser intensity distribution. Sub-diffraction-limit size can be achieved due to the nanoscale material redistribution. Only one pulse was needed in the surface patterning process, thus greatly favoring the efficiency improvement...
December 11, 2017: Optics Express
Wei Chen, Jintao Fan, Aichen Ge, Huanyu Song, Youjian Song, Bowen Liu, Lu Chai, Chingyue Wang, Minglie Hu
We characterize the relative intensity noise (RIN) and relative timing jitter (RTJ) between the signal and pump pulses of optical parametric amplifiers (OPAs) seeded by three different seed sources. Compared to a white-light continuum (WLC) seeded- and an optical parametric generator (OPG) seeded OPA, the narrowband CW seeded OPA exhibits the lowest root-mean-square (RMS) RIN and RTJ of 0.79% and 0.32 fs, respectively, integrated from 1 kHz to the Nyquist frequency of 1.25 MHz. An improved numerical model based on a forward Maxwell equation (FME) is built to investigate the transfers of the pump and seed's noise to the resulting OPAs' intensity and temporal fluctuation...
December 11, 2017: Optics Express
Manuel Valdebran, Brent Martin, Kristen M Kelly
Notable milestones in the treatment of vascular lesions have been achieved over the past century. Many cutaneous vascular lesions can be successfully treated with lightbased devices. In this review, we will discuss the treatment of port-wine birthmarks, lymphatic malformations, infantile hemangiomas, rosacea, venous lakes, pyogenic granulomas, cherry angiomas, and angiofibromas using lasers, total reflection amplification of spontaneous emission of radiation, intense pulsed light, and photodynamic therapy. In addition, for several of these diagnoses, we will review medical therapies that can be combined with light-based devices to provide enhanced results...
December 2017: Seminars in Cutaneous Medicine and Surgery
Francesco Randi, Martina Esposito, Francesca Giusti, Oleg Misochko, Fulvio Parmigiani, Daniele Fausti, Martin Eckstein
We show that, in optical pump-probe experiments on bulk samples, the statistical distribution of the intensity of ultrashort light pulses after interaction with a nonequilibrium complex material can be used to measure the time-dependent noise of the current in the system. We illustrate the general arguments for a photoexcited Peierls material. The transient noise spectroscopy allows us to measure to what extent electronic degrees of freedom dynamically obey the fluctuation-dissipation theorem, and how well they thermalize during the coherent lattice vibrations...
November 3, 2017: Physical Review Letters
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