• JLA Vol:1 Iss:4 (The Use of High‐Frequency Pulsed Laser Diodes in Fringe Type Laser Doppler Anemometry)

    D. Dopheide
    H. Pfeifer
    M. Faber
    G. Taux
    Physikalisch Technische Bundesanstalt (PTB), D‐3300 Braunschweig, Bundesallee 100, Germany

    The benefits obtained by using pulsed laser diodes with repetition rates much higher than the Doppler frequency are described and the advantages over cw‐ and long‐pulse operation are shown. These benefits are achieved by several characteristics of pulsed laser operation. First, in pulsed mode the time‐averaged number of photons may be considerably higher than in cw‐mode. Second, for some of the LDA data acquisition systems the laser pulses can be synchronized with the sampl...


  • JLA Vol:14 Iss:1 (A multi-input and multioutput dynamic model for laser marking of ceramic materials)

    A. A. Peligrad
    E. Zhou
    D. Morton
    Faculty of Technology, Bolton Institute, Deane Road, Bolton BL3 5AB, United Kingdom

    L. Li
    Laser Processing Research Centre, Department of Mechanical Engineering, UMIST, Sackville Street, P.O. Box 88, Manchester M60 1QD, United Kingdom

    There are many process parameters that influence the results of laser marking of ceramic materials. Some parameters should be kept within certain tolerance limits to ensure the expected quality of the laser processing. Hence a closed loop control system may be desirable during the process for quality control. For this, an accurate multi-input and multioutput dynamic...


  • JLA Vol:14 Iss:1 (A procedure for laser hazard classification under the Z136.1-2000 American National Standard for Safe Use of Lasers)

    Robert J. Thomas
    Benjamin A. Rockwell
    Air Force Research Laboratory, Brooks AFB, Texas 78235-5215

    Wesley J. Marshall
    USACHPPM, Aberdeen Proving Ground, Maryland 21010-5422

    Robert C. Aldrich
    Sheldon A. Zimmerman
    Dahlgren Division, Naval Surface Warfare Center, Dahlgren, Virginia 22448-5100

    R. James Rockwell
    Rockwell Laser Industries, Cincinnati, Ohio 45243

    Over the past few years, a comprehensive rewrite of the American National Standard for Safe Use of Lasers (ANSI Z136.1) has been conducted. The ANSI Z136.1 is a user standard, as opposed to a manufacturer standard like the Federal Las...


  • JLA Vol:14 Iss:1 (Cutting of slate tiles by CO<sub>2</sub> laser)

    M. Boutinguiza
    F. Lusquin˜os
    J. Pou
    R. Soto
    F. Quintero
    M. Pe´rez-Amor
    Departamento Fı´sica Aplicada Universidade de Vigo, Lagoas Marcosende 9, E-36200 VIGO, Spain

    K. Watkins
    Laser Engineering Group, Department of Engineering, The University of Liverpool, Liverpool L69 3GH, United Kingdom

    Slate is a natural stone which has the characteristic that shows a well-developed defoliation plane, allowing to easily split it in plates parallel to that plane which are particularly used as tiles for roof building. At present, the manufacturing of slate is mostly manual, bein...


  • JLA Vol:14 Iss:1 (Experimental study on surface decontamination by laser ablation)

    X. Zhou
    K. Imasaki
    H. Furukawa
    C. Yamanaka
    Institute for Laser Technology, 2-6 Yamada-oka, Suita, Osaka 565-0871, Japan

    S. Nakai
    Institute of Laser Engineering, Osaka University, 2-6 Yamada-oka, Suita, Osaka 565-0871, Japan

    A high-power pulsed Nd:YAG laser was employed to irradiate a 20-μm-thick Zn coating on a carbon steel surface. The ablation rate was defined as ablated volume divided by consumed laser energy, and was used to assess ablation cleaning ability. The relationships of ablation rate to laser pulse width and ablation rate to laser fluence were investigated, and optimal processing conditions were dete...


  • JLA Vol:14 Iss:1 (Laser marginal lap microwelding for ultrathin sheet metal)

    J. Du
    School of Optics, Center for Research and Education in Optics and Lasers, Mechanical and Aerospace Engineering Department, University of Central Florida, Orlando, Florida 32816

    J. Longobardi
    Metal Tech Industries, 525 Lawler Street, Iowa Falls, Iowa 50126

    W. P. Latham
    Air Force Research Laboratory, Directed Energy Directorate, 3550 Aberdeen Avenue SE, Kirland AFB, New Mexico 87117-5776

    A. Kar
    School of Optics, Center for Research and Education in Optics and Lasers, Mechanical and Aerospace Engineering Department, University of Central Florida, Orlando, Florida 32816

    Butt welding is practically difficult f...


  • JLA Vol:14 Iss:1 (Melt instabilities during laser surface alloying)

    M. H. McCay
    J. A. Hopkins
    T. D. McCay
    The University of Tennessee Space Institute, Center for Laser Applications, Tullahoma, Tennessee 37388

    The depth of the melt layer during laser surface alloying plays a significant role in the shape of the melt pool. There appear to be critical depths at which the molten layer becomes unstable and alters its shape in response to convective flow patterns. The Marangoni number provides an understanding of the influence of the material properties on convection and subsequently the melt shape, being inversely proportional to depth squared, viscosity, and thermal diffusivity, and directly proportional to the surface t...


  • JLA Vol:14 Iss:1 (Multiple reflection and its influence on keyhole evolution)

    Hyungson Ki
    Pravansu S. Mohanty
    Jyotirmoy Mazumder
    Center for Laser Aided Intelligent Manufacturing, Department of Mechanical Engineering and Applied Mechanics, The University of Michigan, Ann Arbor, Michigan 48109-2125

    In laser drilling and keyhole welding, multiple reflection phenomena determine how the energy is transferred from the laser beam to the workpiece, and, most importantly, all other physics such as fluid flow, heat transfer, and the cavity shape itself depend on these phenomena. In this study, a multiple reflection model inside a self-consistent (or self-evolving) cavity has been developed based on the level set method and ray tracing t...


  • 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:14 Iss:1 (Phosphoric acid activated surface modification of tooth dentine by 9.45 &mu;m transversely excited atmosphere CO<sub>2</sub> laser)

    Kunio Awazu
    Mikio Tanaka
    Institute of Free Electron Laser, Osaka University, 2-9-5, Tsudayamate, Hirakata, Osaka 573-0128, Japan

    Junji Kato
    Department of Pediatric Dentistry, Faculty of Dentistry, Tokyo Medical and Dental-University, Japan

    Tuning a laser wavelength to the stretching vibration of specific biomolecules has some advantages in ablating hard tissue and for surface modification induced by the photothermal or the photomechanical interaction. A tunable pulsed transversely excited atmosphere CO2 laser was tuned to 9.45 μm, which is the stretching vibration of phosphoric acid in hydroxyapatite. Dried cow dentine was irra...