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Low-intensity pulsed laser

Thomas Willemsen, Marco Jupé, Mark Gyamfi, Sebastian Schlichting, Detlev Ristau
Dielectric components are essential for laser applications. Chirped mirrors are applied to compress the temporal pulse broadening crucial in the femtosecond regime. However, the design sensitivity and the electric field distribution of chirped mirrors is complex often resulting in low laser induced damage resistances. An approach is presented to increase the damage resistance of pulse compressing mirrors up to 190% in the NIR spectral range. Layers with critical high field intensity of a binary mirror design are substituted by ternary composites and quantized nanolaminates, respectively...
December 11, 2017: Optics Express
M Kübel, Z Dube, A Yu Naumov, M Spanner, G G Paulus, M F Kling, D M Villeneuve, P B Corkum, A Staudte
Ionization of an atom or molecule by a strong laser field produces suboptical cycle wave packets whose control has given rise to attosecond science. The final states of the wave packets depend on ionization and deflection by the laser field, which are convoluted in conventional experiments. Here, we demonstrate a technique enabling efficient electron deflection, separate from the field driving strong-field ionization. Using a midinfrared deflection field permits one to distinguish electron wave packets generated at different field maxima of an intense few-cycle visible laser pulse...
November 3, 2017: Physical Review Letters
K Hicke, D Brunner, M C Soriano, I Fischer
We investigate the dynamics of semiconductor lasers subject to time-delayed optical feedback from the perspective of dynamical self-injection locking. Based on the Lang-Kobayashi model, we perform an analysis of the well-known Low Frequency Fluctuations (LFFs) in the frequency-intensity plane. Moreover, we investigate a recently found dynamical regime of fragmented LFFs by means of a locking-range analysis, spectral comparison and precursor pulse identification. We show that LFF dynamics can be explained by dynamical optical injection locking due to the delayed optical feedback...
November 2017: Chaos
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 8, 2017: Progress in Biophysics and Molecular 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
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
Ping Zhang, Mei X Wu
Psoriasis is an autoimmune inflammatory skin disease. In the past several decades, phototherapy has been widely used to treat stable psoriatic lesions, including trunk, scalp, arms and legs, and partial nail psoriasis. A variety of light/lasers with different mechanisms of action have been developed for psoriasis including ultraviolet B (UVB), psoralen ultraviolet A (PUVA), pulsed dye laser (PDL), photodynamic therapy (PDT), intense pulsed light (IPL), light-emitting diodes (LED), and so on. Because light/laser each has specific therapeutic and adverse effects, it is important to adequately choose the sources and parameters in management of psoriasis with different pathogenic sites, severities, and duration of the disorder...
October 24, 2017: Lasers in Medical Science
Hea-Ja An, Kyung-Won Kim, Mun-Ho Ryu, Han-Yeong Oh, Nam-Gyun Kim, Kyoung-Jun Park
Low-level light (laser) therapy (LLLT) has been widely researched in the recent past. Existing LLLT studies were performed based on laser. Recently, studies using LED have increased. This study presents a smartphone-driven low-power light-emitting device for use in colour therapy as an alternative medicine. The device consists of a control unit and a colour probe. The device is powered by and communicates with a smartphone using USB On-The-Go (OTG) technology. The control unit controls emitting time and intensity of illumination with the configuration value of a smartphone application...
2017: Journal of Healthcare Engineering
Guillaume Point, Leonid Arantchouk, Emmanuelle Thouin, Jérôme Carbonnel, André Mysyrowicz, Aurélien Houard
Laser filamentation offers a promising way for the remote handling of large electrical power in the form of guided arc discharges. We here report that it is possible to increase by several orders of magnitude the lifetime of straight plasma channels from filamentation-guided sparks in atmospheric air. A 30 ms lifetime can be reached using a low-intensity, 100 mA current pulse. Stability of the plasma shape is maintained over such a timescale through a continuous Joule heating from the current. This paves the way for applications based on the generation of straight, long duration plasma channels, like virtual plasma antennas or contactless transfer of electric energy...
October 23, 2017: Scientific Reports
Kevan L Bell, Parsin Hajireza, Wei Shi, Roger J Zemp
Recently, a new noncontact reflection-mode imaging modality called photoacoustic remote sensing (PARS) microscopy was introduced providing optical absorption contrast. Unlike previous modalities, which rely on interferometric detection of a probe beam to measure surface oscillations, the PARS technique detects photoacoustic initial pressures induced by a pulsed laser at their origin by monitoring intensity modulations of a reflected probe beam. In this paper, a model describing the temporal evolution from a finite excitation pulse is developed with consideration given to the coherence length of the interrogation beam...
June 20, 2017: Applied Optics
Han-Zhen Li, Tong-Pu Yu, Li-Xiang Hu, Yan Yin, De-Bin Zou, Jian-Xun Liu, Wei-Quan Wang, Shun Hu, Fu-Qiu Shao
We propose a novel scheme to generate ultra-bright ultra-short γ-ray flashes and high-energy-density attosecond positron bunches by using multi-dimensional particle-in-cell simulations with quantum electrodynamics effects incorporated. By irradiating a 10 PW laser pulse with an intensity of 10(23) W/cm(2) onto a micro-wire target, surface electrons are dragged-out of the micro-wire and are effectively accelerated to several GeV energies by the laser ponderomotive force, forming relativistic attosecond electron bunches...
September 4, 2017: Optics Express
Liang Mei, Peng Guan, Zheng Kong
Differential absorption lidar (DIAL) technique employed for remote sensing has been so far based on the sophisticated narrow-band pulsed laser sources, which require intensive maintenance during operation. In this work, a continuous-wave (CW) NO2 DIAL system based on the Scheimpflug principle has been developed by employing a compact high-power CW multimode 450 nm laser diode as the light source. Laser emissions at the on-line and off-line wavelengths of the NO2 absorption spectrum are implemented by tuning the injection current of the laser diode...
October 2, 2017: Optics Express
Bo Li, Xiaofeng Li, Dayuan Zhang, Qiang Gao, Mingfa Yao, Zhongshan Li
We demonstrate a femtosecond two-photon laser-induced fluorescence (fs-TPLIF) technique for sensitive CO detection, using a 230 nm pulse of 9 µJ and 45 fs. The advantages of fs-TPLIF in excitation of molecular species were analyzed. Spectra of CO fs-TPLIF were recorded in stable laminar flames spatially resolved across the flame front. A hot band (1, n) together with the conventional band (0, n) of the B→A transitions were observed in the burned zone and attributed to the broadband nature of the fs excitation...
October 16, 2017: Optics Express
Artem E Akmalov, Alexander A Chistyakov, Olga I Dubkova, Gennadii E Kotkovskii, Alexei V Sychev
The approaches for increasing a contact-free sampling distance up to 40 cm for a field asymmetric ion mobility spectrometer were investigated and implemented by use both the vortex flow made by a rotating impeller and the laser desorption of traces of low volatile explosives. The sampling device for a laser-based field asymmetric ion mobility spectrometer including a high-speed rotating impeller was designed and built with help of computer simulation of vortex and analytical flows. The dependence of a signal of trinitrotoluene vapors on a rotational speed of an impeller was obtained...
August 2017: European Journal of Mass Spectrometry
Shaomin Peng, Guichuan Xing, Zikang Tang
Key to optimizing and tailoring the optoelectronic properties of semiconductor nanostructures for practical applications is a clear understanding of their carrier interactions and recombination dynamics. Herein, the electron-hole (e-h) plasma dynamics and the electron-phonon coupling interactions in zincblende ZnTe nanowires (NWs) were systematically investigated by time-resolved photoluminescence (TRPL) spectroscopy over a wide range of lattice temperatures (4-300 K) and pump densities. Following intense, non-resonant femtosecond (fs) laser pulse excitation, the excited carriers thermalize to quasi-equilibrium distribution through carrier-carrier and carrier-phonon scattering within a few picoseconds...
October 19, 2017: Nanoscale
Jean Uwingabiye, Abdelhay Lemnouer, Ignasi Roca, Tarek Alouane, Mohammed Frikh, Bouchra Belefquih, Fatna Bssaibis, Adil Maleb, Yassine Benlahlou, Jalal Kassouati, Nawfal Doghmi, Abdelouahed Bait, Charki Haimeur, Lhoussain Louzi, Azeddine Ibrahimi, Jordi Vila, Mostafa Elouennass
BACKGROUND: Carbapenem-resistant Acinetobacter baumannii has recently been defined by the World Health Organization as a critical pathogen. The aim of this study was to compare clonal diversity and carbapenemase-encoding genes of A. baumannii isolates collected from colonized or infected patients and hospital environment in two intensive care units (ICUs) in Morocco. METHODS: The patient and environmental sampling was carried out in the medical and surgical ICUs of Mohammed V Military teaching hospital from March to August 2015...
2017: Antimicrobial Resistance and Infection Control
Haochuan Wang, Ayman Alismail, Gaia Barbiero, Maximilian Wendl, Hanieh Fattahi
The generation of superoctave spectra from the interaction of intense ultrashort optical pulses and cubic nonlinearity is the result of interplay between the dispersion and nonlinearity of a material and various propagation effects. The cubic nonlinearity can be enhanced when it is combined with a quadratic-cascaded nonlinearity, relaxing the requirement on the laser's peak intensity for supercontinuum (SC) generation. In this Letter, we demonstrate and compare the generation of an SC driven from cubic and cascaded quadratic nonlinearities at an anomalous and zero dispersion wavelength (ZDW)...
July 1, 2017: Optics Letters
Muhammad Waqas Khalid, Rajib Ahmed, Ali K Yetisen, Bader AlQattan, Haider Butt
The optical phase conjugation (OPC) through photonic nanostructures in coherent optics involves the utilization of a nonlinear optical mechanism through real-time processing of electromagnetic fields. Their applications include spectroscopy, optical tomography, wavefront sensing, and imaging. The development of functional and personalized holographic devices in the visible and near-infrared spectrum can be improved by introducing cost-effective, rapid, and high-throughput fabrication techniques and low-cost recording media...
September 6, 2017: Scientific Reports
Leonhard Karsch, Elke Beyreuther, Wolfgang Enghardt, Malte Gotz, Umar Masood, Ulrich Schramm, Karl Zeil, Jörg Pawelke
Only few ten radiotherapy facilities worldwide provide ion beams, in spite of their physical advantage of better achievable tumor conformity of the dose compared to conventional photon beams. Since, mainly the large size and high costs hinder their wider spread, great efforts are ongoing to develop more compact ion therapy facilities. One promising approach for smaller facilities is the acceleration of ions on micrometre scale by high intensity lasers. Laser accelerators deliver pulsed beams with a low pulse repetition rate, but a high number of ions per pulse, broad energy spectra and high divergences...
November 2017: Acta Oncologica
Bianca F Trawitzki, Lothar Lilge, Fellipe A T de Figueiredo, Ana Paula Macedo, João Paulo M Issa
Acute arthritis is an inflammation that affects many joints. The principal treatment options comprise drugs (corticosteroids), invasive and painful surgery. The objective of this study was to evaluate the efficacy of low intensity laser therapy (LILT), a non-invasive treatment, in a murine model of acute inflammation model. 48 mice received a synovial injection of Zymosan A into one knee. Mice were treated with LILT by three different wavelengths, either as a single (S) or dual (D) application immediately after the injury or after 24h following initiation of an inflammatory response...
September 2017: Journal of Photochemistry and Photobiology. B, Biology
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