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https://www.readbyqxmd.com/read/28814822/high-visibility-in-two-color-above-threshold-photoemission-from-tungsten-nanotips-in-a-coherent-control-scheme
#1
Timo Paschen, Michael Förster, Michael Krüger, Christoph Lemell, Georg Wachter, Florian Libisch, Thomas Madlener, Joachim Burgdörfer, Peter Hommelhoff
In this article, we present coherent control of above-threshold photoemission from a tungsten nanotip achieving nearly perfect modulation. Depending on the pulse delay between fundamental ([Formula: see text]) and second harmonic ([Formula: see text]) pulses of a femtosecond fiber laser at the nanotip, electron emission is significantly enhanced or depressed during temporal overlap. Electron emission is studied as a function of pulse delay, optical near-field intensities, DC bias field and final photoelectron energy...
June 17, 2017: Journal of Modern Optics
https://www.readbyqxmd.com/read/28809885/two-photon-absorption-and-subband-photodetection-in-monolayer-mos2
#2
Feng Zhou, Wei Ji
We develop a theoretical model to quantify the two-photon absorption (2 PA) coefficients of monolayer MoS2. Based on two-dimensional excitons, our model reveals the 2 PA coefficient spectrum on the order of 0.01-0.1 cm/MW in the near-infrared for monolayer MoS2. As compared to the band theory for bulk semiconductors, these coefficients are enhanced by at least one order of magnitude. Our model is in agreement with light-intensity-dependent photocurrent measurements on a monolayer MoS2, subband photodetector with femtosecond laser pulses...
August 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28805860/synthesis-of-n-doped-graphene-quantum-dots-by-pulsed-laser-ablation-with-diethylenetriamine-deta-and-their-photoluminescence
#3
S R M Santiago, T N Lin, C H Chang, Y A Wong, C A J Lin, C T Yuan, J L Shen
We report a facile, fast, and one-step approach to prepare N-doped graphene quantum dots (GQDs) using pulsed laser ablation with diethylenetriamine (DETA). The synthesized N-doped GQDs with an average size of about 3.4 nm and an N/C atomic ratio of 26% have been demonstrated. Compared to pristine GQDs, the N-doped GQDs emit enhanced photoluminescence (PL) with a factor as high as 66, originated from the enhanced densities of pyridinic and graphitic N. The temperature-dependent PL of the N-doped GQDs was studied from cryogenic to room temperature...
August 14, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28795742/optical-reconfiguration-and-polarization-control-in-semi-continuous-gold-films-close-to-the-percolation-threshold
#4
Christian Frydendahl, Taavi Repän, Mathias Geisler, Sergey M Novikov, Jonas Beermann, Andrei V Lavrinenko, Sanshui Xiao, Sergey I Bozhevolnyi, N Asger Mortensen, Nicolas Stenger
Controlling and confining light by exciting plasmons in resonant metallic nanostructures is an essential aspect of many new emerging optical technologies. Here we explore the possibility of controllably reconfiguring the intrinsic optical properties of semi-continuous gold films, by inducing permanent morphological changes with a femtosecond (fs)-pulsed laser above a critical power. Optical transmission spectroscopy measurements show a correlation between the spectra of the morphologically modified films and the wavelength, polarization, and the intensity of the laser used for alteration...
August 10, 2017: Nanoscale
https://www.readbyqxmd.com/read/28792549/a-fully-general-time-dependent-multiconfiguration-self-consistent-field-method-for-the-electron-nuclear-dynamics
#5
Ryoji Anzaki, Takeshi Sato, Kenichi L Ishikawa
We present a fully general time-dependent multiconfiguration self-consistent-field method to describe the dynamics of a system consisting of arbitrarily different kinds and numbers of interacting fermions and bosons. The total wave function is expressed as a superposition of different configurations constructed from time-dependent spin-orbitals prepared for each particle kind. We derive equations of motion followed by configuration-interaction (CI) coefficients and spin-orbitals for general, not restricted to full-CI, configuration spaces...
August 9, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28791605/laser-and-light-treatments-for-hair-reduction-in-fitzpatrick-skin-types-iv-vi-a-comprehensive-review-of-the-literature
#6
REVIEW
Rachel A Fayne, Marina Perper, Ariel E Eber, Adam S Aldahan, Keyvan Nouri
Unwanted facial and body hair presents as a common finding in many patients, such as females with hirsutism. With advances in laser and light technology, a clinically significant reduction in hair can be achieved in patients with light skin. However, in patients with darker skin, Fitzpatrick skin types (FST) IV-VI, the higher melanin content of the skin interferes with the proposed mechanism of laser-induced selective photothermolysis, which is to target the melanin in the hair follicle to cause permanent destruction of hair bulge stem cells...
August 8, 2017: American Journal of Clinical Dermatology
https://www.readbyqxmd.com/read/28790410/non-sequential-double-ionization-with-near-single-cycle-laser-pulses
#7
A Chen, M Kübel, B Bergues, M F Kling, A Emmanouilidou
A three-dimensional semiclassical model is used to study double ionization of Ar when driven by a near-infrared and near-single-cycle laser pulse for intensities ranging from 0.85 × 10(14) W/cm(2) to 5 × 10(14) W/cm(2). Asymmetry parameters, distributions of the sum of the two electron momentum components along the direction of the polarization of the laser field and correlated electron momenta are computed as a function of the intensity and of the carrier envelope phase. A very good agreement is found with recently obtained results in kinematically complete experiments employing near-single-cycle laser pulses...
August 8, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28774060/numerical-approach-to-modeling-and-characterization-of-refractive-index-changes-for-a-long-period-fiber-grating-fabricated-by-femtosecond-laser
#8
Akram Saad, Yonghyun Cho, Farid Ahmed, Martin Byung-Guk Jun
A 3D finite element model constructed to predict the intensity-dependent refractive index profile induced by femtosecond laser radiation is presented. A fiber core irradiated by a pulsed laser is modeled as a cylinder subject to predefined boundary conditions using COMSOL5.2 Multiphysics commercial package. The numerically obtained refractive index change is used to numerically design and experimentally fabricate long-period fiber grating (LPFG) in pure silica core single-mode fiber employing identical laser conditions...
November 21, 2016: Materials
https://www.readbyqxmd.com/read/28772389/optically-clear-and-resilient-free-form-%C3%A2%C2%B5-optics-3d-printed-via-ultrafast-laser-lithography
#9
Linas Jonušauskas, Darius Gailevičius, Lina Mikoliūnaitė, Danas Sakalauskas, Simas Šakirzanovas, Saulius Juodkazis, Mangirdas Malinauskas
We introduce optically clear and resilient free-form micro-optical components of pure (non-photosensitized) organic-inorganic SZ2080 material made by femtosecond 3D laser lithography (3DLL). This is advantageous for rapid printing of 3D micro-/nano-optics, including their integration directly onto optical fibers. A systematic study of the fabrication peculiarities and quality of resultant structures is performed. Comparison of microlens resiliency to continuous wave (CW) and femtosecond pulsed exposure is determined...
January 2, 2017: Materials
https://www.readbyqxmd.com/read/28772237/low-intensity-laser-therapy-efficacy-evaluation-in-mice-subjected-to-acute-arthritis-condition
#10
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...
July 26, 2017: Journal of Photochemistry and Photobiology. B, Biology
https://www.readbyqxmd.com/read/28769051/ir-laser-assisted-additive-freeform-optics-manufacturing
#11
Zhihan Hong, Rongguang Liang
Computer-controlled additive manufacturing (AM) processes, also known as three-dimensional (3D) printing, create 3D objects by the successive adding of a material or materials. While there have been tremendous developments in AM, the 3D printing of optics is lagging due to the limits in materials and tight requirements for optical applicaitons. We propose a new precision additive freeform optics manufacturing (AFOM) method using an pulsed infrared (IR) laser. Compared to ultraviolet (UV) curable materials, thermally curable optical silicones have a number of advantages, such as strong UV stability, non-yellowing, and high transmission, making it particularly suitable for optical applications...
August 2, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28762979/in-house-time-resolved-photocrystallography-on-the-millisecond-timescale-using-a-gated-x-ray-hybrid-pixel-area-detector
#12
Nicolas Casaretto, Dominik Schaniel, Paul Alle, Emmanuel Wenger, Pascal Parois, Bertrand Fournier, El Eulmi Bendeif, Cyril Palin, Sébastien Pillet
With the remarkable progress of accelerator-based X-ray sources in terms of intensity and brightness, the investigation of structural dynamics from time-resolved X-ray diffraction methods is becoming widespread in chemistry, biochemistry and materials science applications. Diffraction patterns can now be measured down to the femtosecond time-scale using X-ray free electron lasers or table-top laser plasma X-ray sources. On the other hand, the recent developments in photon counting X-ray area detectors offer new opportunities for time-resolved crystallography...
August 1, 2017: Acta Crystallographica Section B, Structural Science, Crystal Engineering and Materials
https://www.readbyqxmd.com/read/28761761/panretinal-photocoagulation-using-short-pulse-laser-induces-less-inflammation-and-macular-thickening-in-patients-with-diabetic-retinopathy
#13
Yoshihiro Takamura, Shogo Arimura, Seiji Miyake, Takehiro Matsumura, Makoto Gozawa, Kentaro Iwasaki, Masaru Inatani
We compared the effect of panretinal photocoagulation (PRP) using short-pulse laser (SPL) and conventional laser, regardless of the number of spots, in terms of their effect on the progression of diabetic macular edema (DME) and anterior flare intensity (AFI) in patients with high-risk nonproliferative diabetic retinopathy (non-PDR). Forty-two eyes of 42 patients were subjected to PRP using the conventional argon laser (Conv group) or SPL (SPL group). CRT and AFI levels in the SPL group were significantly lower than those in the Conv group (CRT at 4, 6, and 10 weeks; AFI at 6, 10, and 18 weeks)...
2017: Journal of Ophthalmology
https://www.readbyqxmd.com/read/28759831/pulsed-uv-laser-induced-modifications-in-optical-and-structural-characteristics-of-alpha-irradiated-pm-355-ssntd
#14
S S Alghamdi, W A Farooq, M R Baig, M S Algarawi, Talal Mohammed Alrashidi, Syed Mansoor Ali, K Alfaramawi
Pre- and postalpha-exposed PM-355 detectors were irradiated using UV laser with different number of pulses (100, 150, 200, 300, and 400). UV laser beam energy of 20mJ per pulse with a pulse width of 9ns was incident on an area of 19.6mm(2) of the samples. XRD spectra indicated that for both reference and UV-irradiated samples, the structure is amorphous, but the crystallite size increases upon UV irradiation. The same results were obtained from SEM analysis. Optical properties of PM-355 polymeric solid-state nuclear track detectors were also investigated...
July 8, 2017: Applied Radiation and Isotopes
https://www.readbyqxmd.com/read/28759074/fabrication-of-photoluminescent-nc-si-sio2-thin-films-prepared-by-pld
#15
Partha P Dey, Alika Khare
In the present report, the structural, compositional, morphological, and photoluminescence properties of nanostructured non-stoichiometric silicon oxide (nc-Si:SiO2 or SiOx) thin films fabricated by pulsed-laser ablation of silicon in the presence of oxygen pressure, from 10(-4) to 0.5 mbar, are presented. X-ray diffraction spectra and Raman spectra confirmed the formation of nanocrystalline Si within the films while electron diffraction X-ray spectroscopy confirmed the increase in oxygen content with increasing O2 pressure...
August 16, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28752575/ipl-vs-pdl-in-treatment-of-facial-erythema-a-split-face-study
#16
Marc Z Handler, Bradley S Bloom, David J Goldberg
BACKGROUND: Lasers and noncoherent intense pulse light sources effectively treat vascular lesions. Intense pulsed light (IPL), a nonablative treatment for photorejuvenation, uses a flashlamp which emits noncoherent light between 400 and 1400 nm. The light may be filtered to target a specific chromophore. The pulsed dye laser (PDL), at 595 nm, has been the historical standard of care in the treatment of facial erythema. We sought to determine whether IPL may be used in lieu of PDL in reducing facial erythema...
July 27, 2017: Journal of Cosmetic Dermatology
https://www.readbyqxmd.com/read/28751648/effects-of-ultrashort-laser-pulses-on-angular-distributions-of-photoionization-spectra
#17
C H Raymond Ooi, W L Ho, A D Bandrauk
We study the photoelectron spectra by intense laser pulses with arbitrary time dependence and phase within the Keldysh framework. An efficient semianalytical approach using analytical transition matrix elements for hydrogenic atoms in any initial state enables efficient and accurate computation of the photoionization probability at any observation point without saddle point approximation, providing comprehensive three dimensional photoelectron angular distribution for linear and elliptical polarizations, that reveal the intricate features and provide insights on the photoionization characteristics such as angular dispersions, shift and splitting of photoelectron peaks from the tunneling or above threshold ionization(ATI) regime to non-adiabatic(intermediate) and multiphoton ionization(MPI) regimes...
July 27, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28747675/high-energy-mid-infrared-sub-cycle-pulse-synthesis-from-a-parametric-amplifier
#18
Houkun Liang, Peter Krogen, Zhou Wang, Hyunwook Park, Tobias Kroh, Kevin Zawilski, Peter Schunemann, Jeffrey Moses, Louis F DiMauro, Franz X Kärtner, Kyung-Han Hong
High-energy phase-stable sub-cycle mid-infrared pulses can provide unique opportunities to explore phase-sensitive strong-field light-matter interactions in atoms, molecules and solids. At the mid-infrared wavelength, the Keldysh parameter could be much smaller than unity even at relatively modest laser intensities, enabling the study of the strong-field sub-cycle electron dynamics in solids without damage. Here we report a high-energy sub-cycle pulse synthesiser based on a mid-infrared optical parametric amplifier and its application to high-harmonic generation in solids...
July 26, 2017: Nature Communications
https://www.readbyqxmd.com/read/28743976/nano-plasmonic-near-field-phase-matching-of-attosecond-pulses
#19
Tahir Shaaran, Rana Nicolas, Bianca Iwan, Milutin Kovacev, Hamed Merdji
Nano-structures excited by light can enhance locally the electric field when tuned to plasmonic resonances. This phenomenon can be used to boost non-linear processes such as harmonic generation in crystals or in gases, Raman excitation, and four wave mixing. Here we present a theoretical investigation of the near-field phase matching of attosecond pulses emitted by high-order harmonic generation (HHG) of an atom immersed in a multi-cycle femtosecond infrared laser field and a spatially inhomogeneous plasmonic field...
July 25, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28741866/a-review-of-available-laser-and-intense-light-source-home-devices-a-dermatologist-s-perspective
#20
REVIEW
Margit Lw Juhász, Melissa K Levin, Ellen S Marmur
BACKGROUND: Home optical devices are becoming an increasingly popular treatment modality sought out by patients for dermatologic pathologies such as acne, hair removal and anti-aging, as these devices are a low-cost and convenient therapy choice. METHODS: An Internet search using PubMed.gov was completed with search terms, "home device dermatology," "home device acne," "home device hair" or "hair removal," and "home device aging." RESULTS: Currently, there are multiple home optical devices available on the market...
July 25, 2017: Journal of Cosmetic Dermatology
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