• JLA Vol:8 Iss:4 (Acoustic emission from modulated laser beam welding of materials)

    Hongping Gu
    W. W. Duley
    Guelph‐Waterloo Program for Graduate Work in Physics, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1

    Acoustic emission during the laser welding of metals with a modulated CO2 laser beam has been investigated. Sharp resonances at many frequencies in the acoustic emission spectra have been observed. This was most noticeable when the average laser power was high enough to produce full penetration welds whose acoustic emission at high harmonics with frequencies that overlap with bands of vibrational frequencies corresponding to eigenmodes of the keyhole are greatly enhanced. Lower harmonics were not clearly observe...


  • JLA Vol:2 Iss:2 (Infrared Optical Fibers for Surgical Applications)

    R. W. Waynant
    M. N. Ediger
    M. Fink
    Center for Devices and Radiological Health, Food and Drug Administration, 5600 Fishers Lane, Rockville, MD 20857

    The basic characteristics of fibers that are appropriate for surgical use in the infrared are reviewed. New fiber materials, such as sapphire, fluorozirconate and chalcogenide glasses, and polycrystalline fibers are discussed as well as their applicability for surgical procedures.


  • JLA Vol:15 Iss:3 (Continuous wave laser ignition thresholds of coal dust clouds)

    Thomas H. Dubaniewicz
    Kenneth L. Cashdollar
    Gregory M. Green
    National Institute for Occupational Safety and Health, Pittsburgh Research Laboratory, P.O. Box 18070, Pittsburgh, Pennsylvania 15236

    Laser-based instruments are used in areas where coal dust ignition presents a safety hazard. The National Institute for Occupational Safety and Health, Pittsburgh Research Laboratory (NIOSH, PRL) is conducting a study to help determine when an optical beam may be considered a potential ignition source in underground coal mines or coal storage facilities. Researchers conducted experiments to determine threshold igniting powers for Pittsburgh seam bituminous co...


  • JLA Vol:19 Iss:4 (Absorption of laser irradiation in a porous powder layer)

    R. W. McVey
    R. M. Melnychuk
    Department of Engineering Science and Mechanics and the Applied Research Laboratory, Pennsylvania State University, University Park, Pennsylvania 16801

    J. A. Todd
    Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, Pennsylvania 16801

    R. P. Martukanitz
    Applied Research Laboratory, Pennsylvania State University, State College, Pennsylvania 16803

    An analytical relationship was derived to describe the amount of energy absorbed within preplaced powder during the laser deposition process. The relationship, which reflects an exponential decay of Beer&ndas...


  • JLA Vol:24 Iss:4 (Optical trap assisted laser nanostructuring in the near-field of microparticles)

    Ulf Quentin
    Karl-Heinz Leitz
    Lutz Deichmann
    Ilya Alexeev
    Michael Schmidt

    Particle based near-field nanostructuring is an excellent possibility to overcome the optical diffraction limit in laser based material processing. In the near-field of microspheres which are irradiated with pulsed laser radiation, it is possible to generate nanoholes with diameters below 100 nm using a laser wavelength of 800 nm. To improve this approach, it is possible to position the microparticles with an optical trap to generate arbitrary structure geometries. In this paper, the authors describe the basic principle of optical trap assisted na...


  • JLA Vol:5 Iss:2 (Tutorial Guide: Laser Measurement Techniques Guide For Hazard Evaluation. Part 2)

    Terry Lyon
    Laser Microwave Division, U.S. Army Environmental Hygiene Agency

    A tutorial guide is presented to provide uniform guidance when performing radiometric measurements upon laser systems to perform a hazard evaluation. This guide was requested by and presented to the Department of Defense (DOD) Laser System Safety Working Group (LSSWG) to serve as a standardized method when performing hazard evaluations primarily upon tactical and training military laser systems including laser rangefinders and designators. Technical information is provided in detail to select a suitable detector, preform radiometric measurements, assess laser system pointing errors, calculate laser p...


  • JLA Vol:25 Iss:5 (Laser-induced thermoelectric voltage in La<sub>0.9</sub>Pr<sub>0.1</sub>MnO<sub>3</sub> thin films)

    Lisheng Zhang
    Qianqian Hua
    Yan Fang
    Beijing Key Laboratory for Nano-Photonics and Nano-Structure, Capital Normal University, Beijing 100048, People's Republic of China

    The laser-induced thermoelectric voltage (LITV) was observed in La0.9Pr0.1MnO3 thin films grown on the vicinal cut LaAlO3 substrate by pulsed laser deposition for the first time. The detected signals were demonstrated to be originated from the anisotropic Seebeck effect. The largest peak value of the voltage is about 2.4 V, the full width at half-maximum of the temporal voltage peak and the rising time are 300–500 and 40–50 n...


  • JLA Vol:14 Iss:1 (Particle size analysis of material removed during CO<sub>2</sub> laser scabbling of concrete for filtration design)

    L. M. Lobo
    K. Williams
    Optical Engineering Group, Wolfson School of Mechanical and Manufacturing Engineering, Loughborough University, Loughborough, Leicestershire LE11 3TU, United Kingdom

    E. P. Johnson
    Laser Group, Department of Mechanical Engineering, Liverpool University, Liverpool, Merseyside L69 3BX, United Kingdom

    J. T. Spencer
    BNFL, Rutherford House, Risley, Warrington, Cheshire WA3 6AS, United Kingdom

    This article examines the particles formed during optimized laser scabbling of concrete in order to help determine an effective filtration strategy for the process. The laser scabbling technique has been developed ...


  • JLA Vol:18 Iss:2 (CO<sub>2</sub> laser beam cutting of steels: Material issues)

    Murali Manohar
    Mittal Steel USA R&D, East Chicago, Indiana 46312

    Laser beam cutting and its advantages along with its relevance to worldwide trends in manufacturing are introduced. Results of efforts to identify material-related factors that render steel suitable for laser cutting are described. Key material requirements for both hot-strip and discrete plate products have been summarized using data collected over several years based on anecdotal information as well as experimental results. It has become clear that near-zero residual stresses and a minimum level of residual elements (Cu, Ni, and Cr) are necessary to obtain clean pierces and consistent cut quality in thick ...


  • JLA Vol:22 Iss:4 (Two methods for measuring laser beam diameter)

    Wesley J. Marshall
    USAPHC, Aberdeen Proving Ground, Maryland 21010-5403, USA

    Two methods for measuring beam diameter are described with the derivation of the equations that make them valid. These methods are the aperture method and the knife edge technique. These methods have been used for decades; however, many do not have a firm grasp of the basic equations that make the methods valid and therefore cannot use and modify the methods with confidence to produce the desired results. The text derives the equations from basic science and mathematics to clarify the underlying concepts of the methods.



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