• JLA Vol:14 Iss:4 (Determining source size from diode laser systems)


    Authors:
    Wesley J. Marshall
    U.S. Army Center for Health Promotion and Preventive Medicine, Aberdeen Proving Ground, Maryland 21010-5403


    Although hazard classification is performed at predefined distances, the maximum permissible exposure (MPE) for extended-source diode lasers decreases as the distance from the laser increases. The MPE depends on the apparent angular subtense of the source, which is simply the magnified image of the emitting diode. Small diameter beams require special consideration.

    $25.00

  • JLA Vol:18 Iss:4 (Cutaneous sensation threshold for 3.8 μm radiation from a short duration pulsed laser on the calves of human subjects: A pilot study)


    Authors:
    Thomas E. Johnson
    Michael J. Roy
    Department of Environmental and Radiological Health Sciences, Colorado State University, 1618 Campus Delivery, Fort Collins, Colorado 80528 and Department of Medicine, School of Medicine, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, Maryland 20814


    The objective of this study was to determine the threshold for sensing a 3.8 μm laser on the skin. The identification of the skin sensation threshold for invisible lasers is useful in providing scientific guidance to the safety community regarding accidental skin exposures. Knowledge of the level of sensation of lasers might be used to s...

    $25.00

  • JLA Vol:1 Iss:3 (Laser Welding of Plastics in Low and High Gravity Environments)


    Authors:
    R. E. Mueller
    W. W. Duley
    CRESS and Laser Processing Laboratory, York University, Toronto, Ontario, Canada M3J 1P3

    S. MacLean
    M. Garneau
    B. Tryggvason
    Canadian Astronaut Office, National Research Council, Ottawa, Ontario, Canada K1A 0R6

    W. F. J. Evans
    Atmospheric Environment Service, 4905 Dufferin Street, Downsview, Ontario M3H 5T4


    Initial results of a series of laser processing experiments performed under the micro‐gravity conditions supplied by NASA's KC‐135 aircraft are presented. Weld morphologies of polypropylene and polyethylene were obtained under both hyper‐ and hy...

    $25.00

  • JLA Vol:8 Iss:3 (Commonwealth of Independent States (CIS) laser scene and Laser Association (LAS) activities)


    Authors:
    Ivan B. Kovsh
    LAS Headquarters, Moscow, Rozhdestvenkastr, 27, 117485, Russia


    $25.00

  • JLA Vol:2 Iss:3 (Erbium:YAG (2.94 &mu;<em>m) Laser Effects on Dental Tissues</em>)


    Authors:
    James A. Hoke
    E. Jeff Burkes
    Edward D. Gomes
    Myron L. Wolbarsht



    Past trials with soft and calcified tissues have demonstrated that long pulse train (2.5 μs) Er:YAG (2.94 μm) laser may be used to ablate tooth structure of human teeth. Determination of physical and thermal damage to surrounding tissue during removal of enamel and dentin is a primary objective of this study. Extracted human teeth with thermal probes imbedded in the pulp chambers were submitted to cavity preparation using an Erbium YAG laser with water mist. Wavelength selection as well as use of a water mist during the procedure resulted in efficient tissue...

    $25.00

  • JLA Vol:17 Iss:2 (Modeling of laser deposition and repair process)


    Authors:
    Lijun Han
    Kaushik M. Phatak
    F. W. Liou
    Department of Mechanical and Aerospace Engineering, University of Missouri-Rolla, Rolla, Missouri 65409-1350


    Laser aided deposition is a material additive based manufacturing process via metallurgically bonding the deposited material to the substrate. Due to its capability to bond various materials together, it becomes an attractive technology for part repair in small scale. However, the details of the process remain an active area for research because of the complicated interactions involved. In this study, a mathematical model was established to investigate thermal and mass transportation phenomena, which incl...

    $25.00

  • JLA Vol:21 Iss:4 (How the laser started)


    Authors:
    Charles Townes
    Department of Physics, University of California, Berkeley, California 94720


    $25.00

  • JLA Vol:24 Iss:4 (Femtosecond laser-induced periodic surface structures)


    Authors:
    J. Bonse
    J. Kru¨ger
    S. Ho¨hm
    A. Rosenfeld
    Array


    The formation of laser-induced periodic surface structures (LIPSS) in different materials (metals, semiconductors, and dielectrics) upon irradiation with linearly polarized fs-laser pulses (τ ∼ 30–150 fs, λ ∼ 800 nm) in air environment is studied experimentally and theoretically. In metals, predominantly low-spatial-frequency-LIPSS with periods close to the laser wavelength λ are observed perpendicular to the polarization. Under specific irradiation conditions, high-spatial-frequency-LIPSS with sub-100-nm spatial periods (∼λ/10) can be gene...

    $25.00

  • JLA Vol:5 Iss:1 (Single Pass Laser Cutting of Polymers)


    Authors:
    R. Patel
    G. Baisch
    IBM Corporation, GTD, Hopewell Junction, New York


    Since the early 1980's discovery of the ability of excimer lasers to etch polymers precisely and cleanly with minimal thermal damage, excimer lasers have been used actively in the semiconductor industry for various manufacturing processes. In the present study a process for laser cutting of polymers has been investigated. A laser beam of controlled cross&hyphen;sectional shape is imaged onto a polymer surface. The geometry of the cutting path is controlled by precise movement of a sample mounted on a 2&hyphen;axis computer controlled work stage. This type of a process is useful for applications ...

    $25.00

  • JLA Vol:15 Iss:4 (Induction heat treatment of laser welds)


    Authors:
    Claus Bagger
    Joakim Ilsing Sørensen
    Flemming O. Olsen
    Manufacturing Engineering and Management, Materials and Process Technology, Technical University of Denmark, Building 425, DK-2800 Lyngby, Denmark


    In this article, a new approach based on induction heat treatment of flat laser welded sheets is presented. With this new concept, the ductility of high strength steels GA260 with a thickness of 1.8 mm and CMn with a thickness of 2.13 mm is believed to be improved by prolonging the cooling time from 750 to 450 °C. Initially, a simple analytical model was used to calculate the ideal energy contributions from a CO2 high power laser s...

    $25.00

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