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Intensed pulsed laser

Tim Plath, Christoph Lechner, Velizar Miltchev, Philipp Amstutz, Nagitha Ekanayake, Leslie Lamberto Lazzarino, Theophilos Maltezopoulos, Jörn Bödewadt, Tim Laarmann, Jörg Roßbach
Free-electron lasers are unique sources of intense and ultra-short x-ray pulses that led to major scientific breakthroughs across disciplines from matter to materials and life sciences. The essential element of these devices are micrometer-sized electron bunches with high peak currents, low energy spread, and low emittance. Advanced FEL concepts such as seeded amplifiers rely on the capability of analyzing and controlling the electron beam properties with few-femtosecond time resolution. One major challenge is to extract tomographic slice parameters instead of projected electron beam properties...
May 25, 2017: Scientific Reports
Elke Beyreuther, Kerstin Brüchner, Mechthild Krause, Margret Schmidt, Rita Szabo, Jörg Pawelke
BACKGROUND: The long-term aim of developing laser based particle acceleration towards clinical application requires not only substantial technological progress, but also the radiobiological characterization of the resulting ultra-short and ultra-intensive particle beam pulses. After comprehensive cell studies a mouse ear tumour model was established allowing for the penetration of low energy protons (~20 MeV) currently available at laser driven accelerators. The model was successfully applied for a first tumour growth delay study with laser driven electrons, whereby the need of improvements crop out...
2017: PloS One
Yiyang Luo, Jianwei Cheng, Bowen Liu, Qizhen Sun, Lei Li, Songnian Fu, Dingyuan Tang, Luming Zhao, Deming Liu
Physics phenomena of multi-soliton complexes have enriched the life of dissipative solitons in fiber lasers. By developing a birefringence-enhanced fiber laser, we report the first experimental observation of group-velocity-locked vector soliton (GVLVS) molecules. The birefringence-enhanced fiber laser facilitates the generation of GVLVSs, where the two orthogonally polarized components are coupled together to form a multi-soliton complex. Moreover, the interaction of repulsive and attractive forces between multiple pulses binds the particle-like GVLVSs together in time domain to further form compound multi-soliton complexes, namely GVLVS molecules...
May 24, 2017: Scientific Reports
Tsukasa Takanashi, Kosuke Nakamura, Edwin Kukk, Koji Motomura, Hironobu Fukuzawa, Kiyonobu Nagaya, Shin-Ichi Wada, Yoshiaki Kumagai, Denys Iablonskyi, Yuta Ito, Yuta Sakakibara, Daehyun You, Toshiyuki Nishiyama, Kazuki Asa, Yuhiro Sato, Takayuki Umemoto, Kango Kariyazono, Kohei Ochiai, Manabu Kanno, Kaoru Yamazaki, Kuno Kooser, Christophe Nicolas, Catalin Miron, Theodor Asavei, Liviu Neagu, Markus Schöffler, Gregor Kastirke, Xiao-Jing Liu, Artem Rudenko, Shigeki Owada, Tetsuo Katayama, Tadashi Togashi, Kensuke Tono, Makina Yabashi, Hirohiko Kono, Kiyoshi Ueda
Coulomb explosion of diiodomethane CH2I2 molecules irradiated by ultrashort and intense X-ray pulses from SACLA, the Japanese X-ray free electron laser facility, was investigated by multi-ion coincidence measurements and self-consistent charge density-functional-based tight-binding (SCC-DFTB) simulations. The diiodomethane molecule, containing two heavy-atom X-ray absorbing sites, exhibits a rather different charge generation and nuclear motion dynamics compared to iodomethane CH3I with only a single heavy atom, as studied earlier...
May 22, 2017: Physical Chemistry Chemical Physics: PCCP
Omid Zandi, Kyle J Wilkin, Yanwei Xiong, Martin Centurion
We have constructed an experimental setup for gas phase electron diffraction with femtosecond resolution and a high average beam current. While gas electron diffraction has been successful at determining molecular structures, it has been a challenge to reach femtosecond resolution while maintaining sufficient beam current to retrieve structures with high spatial resolution. The main challenges are the Coulomb force that leads to broadening of the electron pulses and the temporal blurring that results from the velocity mismatch between the laser and electron pulses as they traverse the sample...
July 2017: Structural Dynamics (Melville, N.Y.)
Arpit Shrimal, Souvik Sardar, Soumyajit Roychoudhury, Somenath Sarkar
BACKGROUND: Hirsutism means excessive terminal hair growth in a female in male pattern distribution. Perception of hirsutism is subjective. Permanent laser hair reduction is a slow process taking many sessions and tracking of improvement parameters is tedious. Hence, a lot of confusion still exists regarding the type of laser most beneficial for treatment. AIM: The aim of this study was to compare the effectiveness and safety profile of long-pulsed Nd: YAG laser (1064 nm) and intense pulse light (IPL)-755 nm in management of idiopathic facial hirsutism...
January 2017: Journal of Cutaneous and Aesthetic Surgery
Daniel P Friedmann, Mitchel P Goldman, Sabrina G Fabi, Isabella Guiha
Reports of the sequential use of multiple light and laser sources for topical 5-aminolevulinic acid (ALA) activation in photodynamic therapy (PDT) of inflammatory acne vulgaris are lacking. The authors sought to retrospectively compare field-directed ALA-PDT with blue light only, blue light + pulsed dye laser (PDL), blue light + intense pulsed light (IPL), blue light + PDL + IPL, or blue light + red light + PDL + IPL for inflammatory acne of the face or upper trunk. Results showed a trend toward greater patient-reported improvement with comparable tolerability using multiple, sequential light sources in ALA-PDT for acne vulgaris, albeit not statistically significant...
2017: Skinmed
Mirjam Falge, Friedrich Georg Fröbel, Volker Engel, Stefanie Gräfe
If the adiabatic approximation is valid, electrons smoothly adapt to molecular geometry changes. In contrast, as a characteristic of diabatic dynamics, the electron density does not follow the nuclear motion. Recently, we have shown that the asymmetry in time-resolved photoelectron spectra serves as a tool to distinguish between these dynamics [Falge et al., J. Phys. Chem. Lett., 2012, 3, 2617]. Here, we investigate the influence of an additional, moderately intense infrared (IR) laser field, as often applied in attosecond time-resolved experiments, on such asymmetries...
May 19, 2017: Physical Chemistry Chemical Physics: PCCP
Naotaka Yoshikawa, Tomohiro Tamaya, Koichiro Tanaka
The electronic properties of graphene can give rise to a range of nonlinear optical responses. One of the most desirable nonlinear optical processes is high-harmonic generation (HHG) originating from coherent electron motion induced by an intense light field. Here, we report on the observation of up to ninth-order harmonics in graphene excited by mid-infrared laser pulses at room temperature. The HHG in graphene is enhanced by an elliptically polarized laser excitation, and the resultant harmonic radiation has a particular polarization...
May 19, 2017: Science
Benedikt J Daurer, Kenta Okamoto, Johan Bielecki, Filipe R N C Maia, Kerstin Mühlig, M Marvin Seibert, Max F Hantke, Carl Nettelblad, W Henry Benner, Martin Svenda, Nicuşor Tîmneanu, Tomas Ekeberg, N Duane Loh, Alberto Pietrini, Alessandro Zani, Asawari D Rath, Daniel Westphal, Richard A Kirian, Salah Awel, Max O Wiedorn, Gijs van der Schot, Gunilla H Carlsson, Dirk Hasse, Jonas A Sellberg, Anton Barty, Jakob Andreasson, Sébastien Boutet, Garth Williams, Jason Koglin, Inger Andersson, Janos Hajdu, Daniel S D Larsson
This study explores the capabilities of the Coherent X-ray Imaging Instrument at the Linac Coherent Light Source to image small biological samples. The weak signal from small samples puts a significant demand on the experiment. Aerosolized Omono River virus particles of ∼40 nm in diameter were injected into the submicrometre X-ray focus at a reduced pressure. Diffraction patterns were recorded on two area detectors. The statistical nature of the measurements from many individual particles provided information about the intensity profile of the X-ray beam, phase variations in the wavefront and the size distribution of the injected particles...
May 1, 2017: IUCrJ
Atula S D Sandanayaka, Toshinori Matsushima, Fatima Bencheikh, Kou Yoshida, Munetomo Inoue, Takashi Fujihara, Kenichi Goushi, Jean-Charles Ribierre, Chihaya Adachi
The demonstration of continuous-wave lasing from organic semiconductor films is highly desirable for practical applications in the areas of spectroscopy, data communication, and sensing, but it still remains a challenging objective. We report low-threshold surface-emitting organic distributed feedback lasers operating in the quasi-continuous-wave regime at 80 MHz as well as under long-pulse photoexcitation of 30 ms. This outstanding performance was achieved using an organic semiconductor thin film with high optical gain, high photoluminescence quantum yield, and no triplet absorption losses at the lasing wavelength combined with a mixed-order distributed feedback grating to achieve a low lasing threshold...
April 2017: Science Advances
T W Huang, C T Zhou, H Zhang, S Z Wu, B Qiao, X T He, S C Ruan
The hosing processes of a relativistic laser pulse, electron acceleration, and betatron radiation in a parabolic plasma channel are investigated in the direct laser acceleration regime. It is shown that the laser hosing instability would result in the generation of a randomly directed off-axis electron beam and radiation source with a large divergence angle. While employing a preformed parabolic plasma channel, the restoring force provided by the plasma channel would correct the perturbed laser wave front and thus suppress the hosing instability...
April 2017: Physical Review. E
Reza Khazaeinezhad, Meena Siddiqui, Benjamin J Vakoc
We demonstrate a novel high-speed and broadband laser architecture based on stretched pulse active mode locking that provides a wavelength-swept and wavelength-stepped output. The laser utilizes a single intracavity 8.3 meter chirped fiber Bragg grating to generate positive and negative dispersion, and can be operated with or without an intracavity fixed Fabry-Perot etalon to generate wavelength-swept and wavelength-stepped (frequency comb) outputs, respectively. Using a four-path delay line at the output, we achieved 16...
May 15, 2017: Optics Letters
M K Trivedi, F C Yang, B K Cho
Melasma is a dysregulation of the homeostatic mechanisms that control skin pigmentation and excess pigment is produced. Traditional treatment approaches with topical medications and chemical peels are commonly used but due to the refractory and recurrent nature of melasma, patients often seek alternative treatment strategies such as laser and light therapy. Several types of laser and light therapy have been studied in the treatment of melasma. Intense pulsed light, low fluence Q-switched lasers, and non-ablative fractionated lasers are the most common lasers and light treatments that are currently performed...
March 2017: International Journal of Women's Dermatology
Uwe Paasch, Antje Schwandt, Nikolaus Seeber, Gerd Kautz, Sonja Grunewald, Merete Haedersdal
Recent developments (new wavelengths, treatment concepts, and combinations) in the field of lasers, intense pulsed light (IPL), LED, as well as new energy and light sources have opened up new therapeutic options that extend beyond mere aesthetic indications. Thus, while fractional lasers used to be employed to merely treat wrinkles, the same devices - in the context of laser-assisted drug delivery - have now become important tools in the treatment of scars, field cancerization, and epithelial tumors. The requirements posed to physicians, both with respect to establishing the indication and conducting treatment, have been growing along with the increase in technological complexity as well as the rising number of comorbidities and comedications in a patient population that continues to age...
May 2017: Journal der Deutschen Dermatologischen Gesellschaft, Journal of the German Society of Dermatology: JDDG
G Ren, J Yan, J Liu, K Lan, Y H Chen, W Y Huo, Z Fan, X Zhang, J Zheng, Z Chen, W Jiang, L Chen, Q Tang, Z Yuan, F Wang, S Jiang, Y Ding, W Zhang, X T He
We investigate a new laser-driven spherically convergent plasma fusion scheme (SCPF) that can produce thermonuclear neutrons stably and efficiently. In the SCPF scheme, laser beams of nanosecond pulse duration and 10^{14}-10^{15}  W/cm^{2} intensity uniformly irradiate the fuel layer lined inside a spherical hohlraum. The fuel layer is ablated and heated to expand inwards. Eventually, the hot fuel plasmas converge, collide, merge, and stagnate at the central region, converting most of their kinetic energy to internal energy, forming a thermonuclear fusion fireball...
April 21, 2017: Physical Review Letters
Siddharth Karkare, Jun Feng, Xumin Chen, Weishi Wan, F Javier Palomares, T-C Chiang, Howard A Padmore
The generation of intense electron beams with low emittance is key to both the production of coherent x rays from free electron lasers, and electron pulses with large transverse coherence length used in ultrafast electron diffraction. These beams are generated today by photoemission from disordered polycrystalline surfaces. We show that the use of single crystal surfaces with appropriate electronic structures allows us to effectively utilize the physics of photoemission to generate highly directed electron emission, thus reducing the emittance of the electron beam being generated...
April 21, 2017: Physical Review Letters
Qian Cheng, Xiguo Xie, Zongqiang Yuan, Xunqi Zhong, Yunquan Liu, Qihuang Gong, Chengyin Wu
We experimentally and theoretically studied dissociative ionization of argon dimer driven by intense femtosecond laser pulses. In the experiment, we measured the ion yield and the angular distribution of fragmental ions generated from the dissociative ionization channels of (1,1) (Ar2(2+) → Ar(+) + Ar(+)) and (2,1) (Ar2(3+) → Ar(2+) + Ar(+)) using a cold target recoil ion momentum spectroscopy. The channel ratio of (2,1)/(1,1) is 4.5-7.5 times of the yield ratio of double ionization to single ionization of argon monomer depending on the laser intensity...
May 12, 2017: Journal of Physical Chemistry. A
Linlin Wei, Shuaishuai Sun, Cong Guo, Zhongwen Li, Kai Sun, Yu Liu, Wenjian Lu, Yuping Sun, Huanfang Tian, Huaixin Yang, Jianqi Li
Anisotropic lattice movements due to the difference between intralayer and interlayer bonding are observed in the layered transition-metal dichalcogenide 1T-TaSeTe following femtosecond laser pulse excitation. Our ultrafast electron diffraction investigations using 4D-transmission electron microscopy (4D-TEM) clearly reveal that the intensity of Bragg reflection spots often changes remarkably due to the dynamic diffraction effects and anisotropic lattice movement. Importantly, the temporal diffracted intensity from a specific crystallographic plane depends on the deviation parameter s, which is commonly used in the theoretical study of diffraction intensity...
July 2017: Structural Dynamics (Melville, N.Y.)
S Syubaev, A Zhizhchenko, A Kuchmizhak, A Porfirev, E Pustovalov, O Vitrik, Yu Kulchin, S Khonina, S Kudryashov
Donut-shaped laser radiation, carrying orbital angular momentum, namely optical vortex, was recently shown to provide vectorial mass transfer, twisting transiently molten material and producing chiral micro-scale structures on surfaces of different bulk materials upon their resolidification. In this paper, we show that at high-NA focusing nanosecond laser vortices can produce chiral nanoneedles (nanojets) of variable size on thin films of such plasmonic materials, as silver and gold films, covering thermally insulating substrates...
May 1, 2017: Optics Express
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