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Intensed pulsed laser

Yi-Ran Wang, Peng Lee, Bai-Tao Zhang, Yuan-Hua Sang, Jing-Liang He, Hong Liu, Chao-Kuei Lee
Saturable absorbers (SAs) have interesting applications for the realization of pulsed lasers in various wavelengths of fiber and solid-state lasers. Topological insulators (TIs) have been recently discovered to feature saturable absorption due to their unique band structure. In this study, high-purity layers of Bi2Te3 thin film SA have been successfully prepared using the spin coating-coreduction approach (SCCA). Compared with the typical method of preparing SAs, the SCCA can be used to prepare topological insulator saturable absorbers (TISAs) with high optical quality, large area consistency, and controllable thickness, which is critical for pulsed lasers...
November 16, 2017: Nanoscale
Lin Gao, Ni Gao, Wenting Song, Erle Dang, Rong Yin, Li Wang, Gang Wang
<p>Both pulsed dye laser (PDL) and intense pulsed light (IPL) systems have been demonstrated to be effective for treatment of facial telangiectasia, however there have been very few comparative studies between both treatments involving purely Asian patient populations. In this study, we performed a retrospective analysis to compare the efficacy of PDL and IPL systems for the treatment of facial telangiectasia. A total of 416 patients with facial telangiectasia who were treated by PDL or IPLs in our department from August 2012 to March 2015 were included in this study...
November 1, 2017: Journal of Drugs in Dermatology: JDD
Nickolai Zhavoronkov, Mikhail Ivanov
Attosecond (1  as=10(-18)  s) pulses produced through high harmonic generation (HHG) are a basis for studies of electron dynamics during light-matter interaction on an electron's natural time scale. Extensively exploited HHG technology has, however, a few unsolved problems, where producing of circularly polarized or chiral attosecond pulses belongs to them. We have demonstrated experimentally a way to control the ellipticity of attosecond pulse trains produced via HHG in two-color, bi-circular laser fields...
November 15, 2017: Optics Letters
Youssef Korani, Hassan Sabzyan
The effects of the orientation, wavelength and carrier-envelope phase of laser pulses on the spin fluctuation in HeH(2+) and LiH(3+) molecular ions in their bound electronic states, during their interactions with linearly polarized intense laser pulses, were investigated by solving numerically the time-dependent Dirac equation with the Foldy-Wouthuysen transformation. The results of this study showed that an increase in the wavelength of the laser pulse at a fixed intensity reduces the lifetime of the coherent spin states and increases the sensitivity of the spin vector to the applied laser field in both HeH(2+) and LiH(3+) species...
November 15, 2017: Physical Chemistry Chemical Physics: PCCP
E G Maksimov, N N Sluchanko, Y B Slonimskiy, E A Slutskaya, A V Stepanov, A M Argentova-Stevens, E A Shirshin, G V Tsoraev, K E Klementiev, O V Slatinskaya, E P Lukashev, T Friedrich, V Z Paschenko, A B Rubin
The 35-kDa Orange Carotenoid Protein (OCP) is responsible for photoprotection in cyanobacteria. It acts as a light intensity sensor and efficient quencher of phycobilisome excitation. Photoactivation triggers large-scale conformational rearrangements to convert OCP from the orange OCP(O) state to the red active signaling state, OCP(R), as demonstrated by various structural methods. Such rearrangements imply a complete, yet reversible separation of structural domains and translocation of the carotenoid. Recently, dynamic crystallography of OCP(O) suggested the existence of photocycle intermediates with small-scale rearrangements that may trigger further transitions...
November 14, 2017: Scientific Reports
Magdalena Ulmeanu, Robert L Harniman, Petko Petkov, Michael N R Ashfold
Single, or isolated small arrays of, spherical silica colloidal particles (with refractive index ncolloid = 1.47 and radius R = 350 nm or 1.5 μm) were placed on a silicon substrate and immersed in carbon tetrachloride (nliquid = 1.48) or toluene (nliquid = 1.52). Areas of the sample were then exposed to a single laser pulse (8 ps duration, wavelength λ = 355 nm), and the spatial intensity modulation of the near field in the vicinity of the particles revealed via the resulting patterning of the substrate surface...
November 14, 2017: Materials
Xiaofeng Weng, Tengfei Li, Zheqiang Zhong, Bin Zhang
In the radial smoothing (RS) scheme, small-scale self-focusing (SSSF) can degrade beam quality of a pump beam with a Gaussian pulse train, resulting in the degradation of the smoothing performance of the RS scheme. Considering SSSF of the pump beam in an optical Kerr medium (OKM), the propagation model of the laser beam in the RS scheme has been developed, and the effects of the characteristics of the pump beam and the thickness of the optical Kerr medium on the RS performance have further been numerically simulated and analyzed...
November 10, 2017: Applied Optics
Martin Jirka, Ondrej Klimo, Marija Vranic, Stefan Weber, Georg Korn
The intensities of the order of 10(23-24) W/cm(2) are required to efficiently generate electron-positron pairs in laser-matter interaction when multiple laser beam collision is employed. To achieve such intense laser fields with the upcoming generation of 10 PW laser beams, focusing to sub-micron spot size is required. In this paper, the possibility of pair production cascade development is studied for the case of a standing wave created by two tightly focused colliding laser pulses. Even though the stronger ponderomotive force expels the seed particles from the interaction volume when a tightly focused laser beam is used, tight focusing allows to achieve cascade pair production due to the higher intensity in the focal spot...
November 10, 2017: Scientific Reports
Mohammad Bayat, Amarjit Virdi, Fatemehalsadat Rezaei, Sufan Chien
To compare the in vitro effectiveness of Low-Level Laser Therapy (LLLT) and Low Intensity Pulsed Ultrasound (LIPUS) on bony cells and related stem cells. In this study, we aim to systematically review the published scientific literature which explores the use of LLLT and LIPUS to biostimulate the activity or the proliferation of bony cells or stem cells in vitro. We searched the database PubMed for LLLT or LIPUS, with/without bone, osteoblast, osteocyte, stem cells, the human osteosarcoma cell line (MG63), bone-forming cells, and cell culture (or in vitro)...
November 7, 2017: Progress in Biophysics and Molecular Biology
H Olof Jönsson, Carl Caleman, Jakob Andreasson, Nicuşor Tîmneanu
Serial femtosecond crystallography is an emerging and promising method for determining protein structures, making use of the ultrafast and bright X-ray pulses from X-ray free-electron lasers. The upcoming X-ray laser sources will produce well above 1000 pulses per second and will pose a new challenge: how to quickly determine successful crystal hits and avoid a high-rate data deluge. Proposed here is a hit-finding scheme based on detecting photons from plasma emission after the sample has been intercepted by the X-ray laser...
November 1, 2017: IUCrJ
Ning Li, Yueming Zhou, Xiaomeng Ma, Min Li, Cheng Huang, Peixiang Lu
Using the classical ensemble model, we systematically investigate strong-field nonsequential double ionization (NSDI) of Mg by intense elliptically polarized laser pulses with different wavelengths. Different from the noble atoms, NSDI occurs for Mg driven by elliptically and circularly polarized laser fields. Our results show that in elliptically and circularly polarized laser fields, the NSDI yield is sharply suppressed as the wavelength increases. Interestingly, the correlated behavior in the electron momentum spectra depends sensitively on the wavelengths...
November 7, 2017: Journal of Chemical Physics
Koichi Iwata, Masahide Terazima, Hiroshi Masuhara
Novel methodologies utilizing pulsed or intense CW irradiation obtained from lasers have a major impact on biological sciences. In this article, recent development in biophysical researches fully utilizing the laser irradiation is described for three topics, time-resolved fluorescence spectroscopy, time-resolved thermodynamics, and manipulation of the biological assemblies by intense laser irradiation. First, experimental techniques for time-resolved fluorescence spectroscopy are concisely explained in Section 2...
November 3, 2017: Biochimica et Biophysica Acta
H Zhang, B F Shen, W P Wang, S H Zhai, S S Li, X M Lu, J F Li, R J Xu, X L Wang, X Y Liang, Y X Leng, R X Li, Z Z Xu
We present experimental studies on ion acceleration using an 800-nm circularly polarized laser pulse with a peak intensity of 6.9×10^{19}  W/cm^{2} interacting with an overdense plasma that is produced by a laser prepulse ionizing an initially ultrathin plastic foil. The proton spectra exhibit spectral peaks at energies up to 9 MeV with energy spreads of 30% and fluxes as high as 3×10^{12}  protons/MeV/sr. Two-dimensional particle-in-cell simulations reveal that collisionless shocks are efficiently launched by circularly polarized lasers in exploded plasmas, resulting in the acceleration of quasimonoenergetic proton beams...
October 20, 2017: Physical Review Letters
James R McLaughlan, David M J Cowell, Steven Freear
High intensity focused ultrasound (HIFU) or focused ultrasound surgery (FUS) is a non-invasive technique for the treatment of cancerous tissue, which is limited by difficulties in getting real-time feedback on treatment progress and long treatment durations. The formation and activity of acoustic cavitation, specifically inertial cavitation, during HIFU exposures has been demonstrated to enhance heating rates. However, without the introduction of external nuclei its formation an activity can be unpredictable, and potentially counterproductive...
November 3, 2017: Physics in Medicine and Biology
J Wätzel, J Berakdar
Irradiating intercalated nanorings by optical vortices ignites a charge flow that emits coherent trains of high harmonic bursts with frequencies and time structures that are controllable by the topological charge of the driving vortex beam. Similar to synchrotron radiation, the polarization of emitted harmonics is also selectable by tuning to the appropriate emission angle with respect to the ring plane. The nonequilibrium orbital magnetic moment triggered in a ring tunnels quantum mechanically to smaller and larger rings leading respectively to high and low-frequency harmonic generation...
October 30, 2017: Optics Express
Ruirui Zhao, Ding Wang, Yu Zhao, Yuxin Leng, Ruxin Li
A method of temporally compressing picosecond pulses is proposed. To increase the spectral broadening, two picosecond pulses at different central wavelengths are overlapped spatiotemporally to induce a modulation on the intensity envelope, thus leading to a high temporal intensity gradient. The combined pulse is then coupled into a gas-filled hollow-core fiber (HCF) to broaden the spectrum through nonlinear propagation. After that the pulse can be compressed by chirp compensation. This method is demonstrated numerically with two 1-ps/5-mJ pulses centered at 1053- and 1064-nm, respectively, which are coupled into a 250-μm-inner-diameter, 1-m-long HCF filled with 5-bar neon...
October 30, 2017: Optics Express
Thomas Gaumnitz, Arohi Jain, Yoann Pertot, Martin Huppert, Inga Jordan, Fernando Ardana-Lamas, Hans Jakob Wörner
Attosecond metrology has so far largely remained limited to titanium:sapphire lasers combined with an active stabilization of the carrier-envelope phase (CEP). These sources limit the achievable photon energy to ∼100 eV which is too low to access X-ray absorption edges of most second- and third-row elements which are central to chemistry, biology and material science. Therefore, intense efforts are underway to extend attosecond metrology to the soft-X-ray (SXR) domain using mid-infrared (mid-IR) drivers. Here, we introduce and experimentally demonstrate a method that solves the long-standing problem of the complete temporal characterization of ultra-broadband (≫10 eV) attosecond pulses...
October 30, 2017: Optics Express
Alexander Gorel, Koji Motomura, Hironobu Fukuzawa, R Bruce Doak, Marie Luise Grünbein, Mario Hilpert, Ichiro Inoue, Marco Kloos, Gabriela Kovácsová, Eriko Nango, Karol Nass, Christopher M Roome, Robert L Shoeman, Rie Tanaka, Kensuke Tono, Yasumasa Joti, Makina Yabashi, So Iwata, Lutz Foucar, Kiyoshi Ueda, Thomas R M Barends, Ilme Schlichting
Serial femtosecond crystallography at X-ray free-electron lasers (XFELs) offers unprecedented possibilities for macromolecular structure determination of systems prone to radiation damage. However, de novo structure determination, i.e., without prior structural knowledge, is complicated by the inherent inaccuracy of serial femtosecond crystallography data. By its very nature, serial femtosecond crystallography data collection entails shot-to-shot fluctuations in X-ray wavelength and intensity as well as variations in crystal size and quality that must be averaged out...
October 27, 2017: Nature Communications
S Huang, Y Ding, Y Feng, E Hemsing, Z Huang, J Krzywinski, A A Lutman, A Marinelli, T J Maxwell, D Zhu
A simple method for generating single-spike hard x-ray pulses in free-electron lasers (FELs) has been developed at the Linac Coherent Light Source (LCLS). This is realized by nonlinear bunch compression using 20-pC bunch charge, demonstrated in the hard x-ray regime at 5.6 and 9 keV, respectively. Measurements show about half of the FEL shots containing a single-spike spectrum. At 5.6-keV photon energy, the single-spike shots have a mean pulse energy of about 10  μJ with 70% intensity fluctuation and the pulse full width at half maximum is evaluated to be at 200-as level...
October 13, 2017: Physical Review Letters
Xi Xing, Roberto Rey-de-Castro, Herschel Rabitz
In quantum control experiments with shaped femtosecond laser pulses, adaptive feedback control is often used to identify pulse shapes that can optimally steer the quantum system toward the desired outcome. However, gaining mechanistic information can pose a challenge due to the varied structural features of the control pulses and/or the often complex nature of the associated simulations of the experiments. In this article, we introduce control pulse slicing (CPS) as an easy-to-implement experimental analysis tool that can be employed directly in the laboratory without the need for modeling, to gain mechanistic insights about control experiments, regardless of whether the pulse is optimal or chosen by other means...
November 3, 2017: Journal of Physical Chemistry. A
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