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Femtosecond laser

G K Selikhanov, M S Fando, M V Dontsova, A G Gabdulkhakov
This review contains recent data on serial femtosecond X-ray crystallography (SFX), based on a femtosecond X-ray free electron laser, as well as, on the possibilities of its application for studying photosensitive proteins. Development of this method began rather recently, and it has already shown its effectiveness and some unique advantages over conventional X-ray structural analysis. This technology is especially promising for structural studies of membrane proteins and for kinetic studies. The main principle of the method, the possibility of its application in structural biology, its advantages and disadvantages, as well as its prospects for further development are analyzed in this review...
January 2018: Biochemistry. Biokhimii︠a︡
K Beltako, F Michelini, N Cavassilas, L Raymond
Nanoscale molecular-electronic devices and machines are emerging as promising functional elements, naturally flexible and efficient, for next-generation technologies. A deeper understanding of carrier dynamics in molecular junctions is expected to benefit many fields of nanoelectronics and power devices. We determine time-resolved charge current flowing at the donor-acceptor interface in molecular junctions connected to metallic electrodes by means of quantum transport simulations. The current is induced by the interaction of the donor with a Gaussian-shape femtosecond laser pulse...
March 14, 2018: Journal of Chemical Physics
Benjamin Stauch, Vadim Cherezov
G protein-coupled receptors (GPCRs) represent a large superfamily of membrane proteins that mediate cell signaling and regulate a variety of physiological processes in the human body. Structure-function studies of this superfamily were enabled a decade ago by multiple breakthroughs in technology that included receptor stabilization, crystallization in a membrane environment, and microcrystallography. The recent emergence of X-ray free-electron lasers (XFELs) has further accelerated structural studies of GPCRs and other challenging proteins by overcoming radiation damage and providing access to high-resolution structures and dynamics using micrometer-sized crystals...
March 15, 2018: Annual Review of Biophysics
Can Cihan, Abdullah Muti, Isinsu Baylam, Askin Kocabas, Umit Demirbas, Alphan Sennaroglu
We report, to the best of our knowledge, the shortest femtosecond pulses generated from a Kerr-lens mode-locked (KLM) Alexandrite laser operating near 750 nm. The Alexandrite gain medium was pumped with a continuous-wave (cw), 532 nm laser, and the performance of both the short and extended resonators was investigated. The use of an extended cavity eliminated the multi-wavelength spectral instabilities observed during the cw operation of the short cavity. Furthermore, since the repetition rate of the Alexandrite laser was reduced from 107 to 5...
March 15, 2018: Optics Letters
N K Stevenson, C T A Brown, J-M Hopkins, M D Dawson, C Kränkel, A A Lagatsky
We report on the first demonstration, to the best of our knowledge, of a diode-pumped Tm:LuScO3 laser. Efficient and broadly tunable continuous wave operation in the 1973-2141 nm region and femtosecond mode-locking through the use of an ion-implanted InGaAsSb quantum-well-based semiconductor saturable absorber mirror are realized. When mode-locked, near-transform-limited pulses as short as 170 fs were generated at 2093 nm with an average output power of 113 mW and a pulse repetition frequency of 115.2 MHz...
March 15, 2018: Optics Letters
B E Malyugin, N S Anisimova
In certain cases intraoperative pupil dilation during cataract surgery may be necessary to improve the visualization of intraocular structures and assure the atraumatic nature of surgical manipulations. The article reviews a wide range of pupil expanders, their historical aspects and possibilities of their application in modern cataract surgery.
2018: Vestnik Oftalmologii
N P Pashtaev, N A Pozdeeva, V V Zotov, M V Sinitsyn, M A Shcheglova
AIM: to conduct a comparative experimental study of the effect of the use of intracorneal implants during femtosecond laser-assisted intrastromal pocket (IP) and intrastromal tunnel (IT) formation on the strength properties of the cornea. MATERIAL AND METHODS: The experimental study was performed on 24 corneas of 12 rabbit eyes enucleated 1 month after slaughtering. All eyes were divided into 6 groups according to the method of operation. IP and IT were created with IntraLase FS 60 kHz femtolaser...
2018: Vestnik Oftalmologii
Zhaoxiang Liu, Jinping Yao, Jinming Chen, Bo Xu, Wei Chu, Ya Cheng
The generation of laserlike narrow bandwidth emissions from nitrogen molecular ions (N_{2}^{+}) generated in intense near- and mid infrared femtosecond laser fields has aroused much interest because of the mysterious physics underlying such a phenomenon. Here, we perform a pump-probe measurement on the nonlinear interaction of rotational quantum wave packets of N_{2}^{+} generated in midinfrared (e.g., at a wavelength centered at 1580 nm) femtosecond laser fields with an ultrashort probe pulse whose broad spectrum overlaps both P- and R-branch rotational transition lines between the electronic states N_{2}^{+}(B^{2}Σ_{u}^{+},v^{'}=0) and N_{2}^{+}(X^{2}Σ_{g}^{+},v=0)...
February 23, 2018: Physical Review Letters
Khaldoun Saleh, Jacques Millo, Baptiste Marechal, Benoît Dubois, Ahmed Bakir, Alexandre Didier, Clément Lacroûte, Yann Kersalé
A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.
March 14, 2018: Scientific Reports
Alden Curtis, Chase Calvi, James Tinsley, Reed Hollinger, Vural Kaymak, Alexander Pukhov, Shoujun Wang, Alex Rockwood, Yong Wang, Vyacheslav N Shlyaptsev, Jorge J Rocca
Nuclear fusion is regularly created in spherical plasma compressions driven by multi-kilojoule pulses from the world's largest lasers. Here we demonstrate a dense fusion environment created by irradiating arrays of deuterated nanostructures with joule-level pulses from a compact ultrafast laser. The irradiation of ordered deuterated polyethylene nanowires arrays with femtosecond pulses of relativistic intensity creates ultra-high energy density plasmas in which deuterons (D) are accelerated up to MeV energies, efficiently driving D-D fusion reactions and ultrafast neutron bursts...
March 14, 2018: Nature Communications
J S Green, N Booth, R J Dance, R J Gray, D A MacLellan, A Marshall, P McKenna, C D Murphy, C P Ridgers, A P L Robinson, D Rusby, R H H Scott, L Wilson
A key issue in realising the development of a number of applications of high-intensity lasers is the dynamics of the fast electrons produced and how to diagnose them. We report on measurements of fast electron transport in aluminium targets in the ultra-intense, short-pulse (<50 fs) regime using a high resolution temporally and spatially resolved optical probe. The measurements show a rapidly (≈0.5c) expanding region of Ohmic heating at the rear of the target, driven by lateral transport of the fast electron population inside the target...
March 14, 2018: Scientific Reports
Yang Bai, Hannelore Bové, Tim S Nawrot, Benoit Nemery
BACKGROUND: Carbon load in airway macrophages (AM) has been proposed as an internal marker to assess long-term exposure to combustion-derived pollutant particles. However, it is not known how this biomarker is affected by changes in exposure. We studied the clearance kinetics of black carbon (BC) in AM, obtained by sputum induction, in a one-year panel study. METHODS: AM BC was measured 8 times with 6 weeks intervals in healthy young subjects: 15 long-term residents in Leuven, Belgium (BE, mean annual PM10 20-30 μg/m3 ) and 30 newcomers having arrived recently (< 3 weeks) in Leuven from highly polluted cities (mean annual PM10  > 50 μg/m3 ) in low and middle-income countries (LMIC, n = 15), or from low to moderately polluted cities in high-income countries (HIC, n = 15)...
March 14, 2018: Particle and Fibre Toxicology
Mehdi Shajari, Emanuel Wanner, Vladimir Rusev, Shervin Mir Mohi Sefat, Wolfgang J Mayer, Thomas Kohnen, Siegfried Priglinger, Daniel Kook
PURPOSE: To compare corneal densitometry values after Femtosecond Laser-Assisted In Situ Keratomileusis (Fs-LASIK) and Small Incision Lenticule Extraction (SMILE) using Scheimpflug Imaging. METHODS: Our retrospective clinical trial included a total of 146 eyes where 57 eyes underwent Fs-LASIK and 89 eyes underwent SMILE. Examinations with a Pentacam Scheimpflug device (Oculus, Wetzlar, Germany) were performed before surgery, 1 week, 1 month, 3 months, 6 months, and 1 year after surgery...
March 14, 2018: Current Eye Research
Ana R Bastos, Carlos M S Vicente, Rui Oliveira-Silva, Nuno J O Silva, Marta Tacão, João P da Costa, Mário Lima, Paulo S André, Rute A S Ferreira
The development of portable low-cost integrated optics-based biosensors for photonics-on-a-chip devices for real-time diagnosis are of great interest, offering significant advantages over current analytical methods. We report the fabrication and characterization of an optical sensor based on a Mach-Zehnder interferometer to monitor the growing concentration of bacteria in a liquid medium. The device pattern was imprinted on transparent self-patternable organic-inorganic di-ureasil hybrid films by direct UV-laser, reducing the complexity and cost production compared with lithographic techniques or three-dimensional (3D) patterning using femtosecond lasers...
March 12, 2018: Sensors
Thonimar Vieira Alencar, Driele von Dreifus, Maria Gabriela Cota Moreira, Gomes S N Eliel, Chao-Hui Yeh, Po-Wen Chiu, Marcos A Pimenta, Leandro Malard, Ana M de Paula
We report on photoluminescence emission imaging by femtosecond laser excitation on twisted bilayer graphene samples. The emission images are obtained by tuning the excitation laser energies in the near infrared region. We demonstrate an increase of the photoluminescence emission at excitation energies that depends on the bilayer twist angle. The results show a peak for the light emission when the excitation is in resonance with transitions at the van Hove singularities in the electronic density of states. We measured the photoluminescence excitation peak position and width for samples with various twist angles showing resonances in the energy range of 1...
March 13, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Juan Prieto-Pena, Faustino Gomez, Diego M Gonzalez-Castano, Maria Teresa Flores Arias, Justo Arines, Carmen Bao-Varela, Ferran Cambronero-López, Alejandra Martínez Maqueira
Present work describes the radiation quality and dosimetric characterization performed on the micromachining station of the femtosecond STELA (Santiago TErawattLAser) of the University of Santiago de Compostela (Spain). For this aim, ionisation chambers, solid state detectors and radiochromic films were used. The results show the emission of pulsed X-ray produced by laser-accelerated electrons from the ablated material exhibiting both bremsstrahlung and characteristic radiation. Although this radiation was produced unintentionally, a high superficial dose rate can be achieved...
March 13, 2018: Journal of Radiological Protection: Official Journal of the Society for Radiological Protection
Assaf Gershoni, Michael Mimouni, Eitan Livny, Irit Bahar
PURPOSE: The aim of the study was to examine the outcomes of transepithelial photorefractive keratectomy (Trans-PRK) and Femtosecond Laser-assisted in situ keratomileusis (Z-LASIK) for the correction of high myopia. METHODS: A retrospective cohort study design was used. The study group included 792 eyes with high-grade myopia (- 6.0 diopters or higher) or high-grade myopia with astigmatism that were treated with Z-LASIK or Trans-PRK in 2013 through 2014 in an optical outpatient clinic of a large private medical service...
March 12, 2018: International Ophthalmology
Mamoru Endo, Tyko D Shoji, Thomas R Schibli
We demonstrate the use of two dual-output Mach-Zehnder modulators (DO-MZMs) in a direct comparison between a femtosecond (fs) pulse train and a microwave signal. Through balanced detection, the amplitude-to-phase modulation (AM-PM) conversion effect is suppressed by more than 40 dB. A cross-spectrum technique enables us to achieve a high-sensitivity phase noise measurement (-186 dBc/Hz above 10-kHz offset), which corresponds to the thermal noise of a +9 dBm carrier. This method is applied to compare a 1-GHz fs monolithic laser to a 1-GHz microwave signal generated from photodetection of a free-running 500 MHz mode-locked laser...
March 12, 2018: Scientific Reports
Andrey Okhrimchuk, Sergey Fedotov, Ivan Glebov, Vladimir Sigaev, Peter Kazansky
A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.
March 12, 2018: Scientific Reports
Jukun Liu, Xin Jia, Weishu Wu, Ke Cheng, Donghai Feng, Shian Zhang, Zhenrong Sun, Tianqing Jia
This paper reports the ultrafast imaging on the formation of periodic surface ripples induced by a single 800 nm, 50 fs laser pulse. The evolution process is observed on a Si surface with a prefabricated nanogroove. The ripples emerge very quickly, only 3 ps after the laser pulse with a fluence of 0.18 J/cm2 irradiating on the surface, and last for several hundreds of picoseconds. The ultrafast dynamics of laser-matter interaction, such as free carrier excitation, carrier and lattice heating, surface plasmon polariton (SPP) excitation, etc, are studied theoretically...
March 5, 2018: Optics Express
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