JLA Vol:16 Iss:2 (The influence of the pulse length on the drilling of metals with an excimer laser)
Authors:
Aart Schoonderbeek
Array
Cornelis A. Biesheuvel
Ramon M. Hofstra
Nederlands Centrum voor Laser Research (NCLR) B.V., P.O. Box 2662, Enschede, The Netherlands
Klaus-J. Boller
Johan Meijer
ArrayLaser parameters, which significantly influence laser-material interaction processes, are the wavelength, the energy, and the power density. Additionally, there are parameters, like the pulse length, which also strongly influence processing speed and quality. Studies where different types of lasers have been used indicate that long pulses are beneficial for processing speed. However, when different types of laser syst...
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JLA Vol:16 Iss:3 (A procedure for the estimation of intrabeam hazard distances and optical density requirements under the ANSI Z136.1-2000 Standard)
Authors:
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
Mary F. Gorschboth
Sheldon A. Zimmerman
Dahlgren Division, Naval Surface Warfare Center, Dahlgren, Virginia 22448-5100
R. James Rockwell
Rockwell Laser Industries, Cincinnati, Ohio 45243Over the past few years, a comprehensive rewrite of the American National Standard for Safe Use of Lasers (ANSI Z136.1) has been conducted [American National Standards Institute, Z136.1-2000 America...
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JLA Vol:16 Iss:3 (Cementum melting after dye-assisted holmium laser irradiation)
Authors:
L. Bachmann
W. Rossi
D. M. Zezell
Centro de Lasers e Aplicac¸o˜es (CLA), Instituto de Pesquisas Energe´ticas e Nucleares (IPEN), Av. Lineu Prestes, 2242 Cidade Universita´ria 05508-900 Sa˜o Paulo-SP, BrazilDye-assisted laser irradiation with black ink or vegetable coal has been used in procedures involving hard tissue irradiation using neodymium or diode lasers. The objective of this work is to evaluate the human root surface melting, after dye-assisted holmium irradiation with subablative fluences. Human cervical root regions were selected, irradiated with a holmium laser with emission at 2.065 μm, pulse width of 40...
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JLA Vol:16 Iss:3 (Diode laser beam absorption in laser transformation hardening of low alloy steel)
Authors:
Henrikki Pantsar
Veli Kujanpa¨a¨
Laser Processing Laboratory, Lappeenranta University of Technology, FIN 53851 Lappeenranta, FinlandDefining and controlling the absorption of the laser beam is important since all of the heating energy is brought to the material through absorption. Even small variations in the absorption change the laser power needed by hundreds of W. In this study the absorption of a diode laser beam to low alloy steel has been measured by a liquid calorimeter and the surface temperature has been measured with a dual wavelength pyrometer. The varied processing parameters were the power intensity of the beam, the interaction time, and the...
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JLA Vol:16 Iss:3 (Eye hazard characterization of an optical klystron free electron laser beam)
Authors:
Ben E. Edwards
Radiation Safety Division, Duke University Medical Center, Durham, North Carolina 27710
Igor V. Pinayev
Patrick W. Wallace
Free Electron Laser Laboratory, Duke University, Durham, North Carolina 27710A free electron laser (FEL) uses an accelerated electron beam to generate laser light. By adjusting the electron beam energy and other parameters, FELs can generate tunable, coherent light over a range from ultraviolet to millimeter wavelengths. Many FELs are building-sized systems that remain at the site of construction, and are not produced for sale or commercial distribution. Federal laser regulatory requirements for hazard ch...
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JLA Vol:16 Iss:3 (Laser microspot welding of copper)
Authors:
S. Amorosi
Th. Sidler
R. P. Salathe´
Advanced Photonics Laboratory, Ecole Polytechnique Fe´de´rale de Lausanne, Switzerland
H. P. Schwob
J. Hertzberg
LASAG AG, Thun, SwitzerlandWe describe a novel procedure for highly reliable microspot welding of copper based on a calibrated on-line reflectivity measurement. This parameter is used to control the laser power slope and the weld spot diameter. Reliable welds are obtained without the need of other active control mechanisms. The new technique allows realizing welds with a diameter close to the laser beam waist and leads to a reduction in the relative ...
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JLA Vol:16 Iss:3 (Laser synthesizing NiAl intermetallic and TiC reinforced NiAl intermetallic matrix composite)
Authors:
Minlin Zhong
Laser Processing and Rapid Prototyping Research Center, Department of Mechanical Engineering, Tsinghua University, Beijing, 100084, China
Xiangyang Xu
Laboratory for Surface Modification, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100080, China
Wenjin Liu
Hongqing Sun
Laser Processing and Rapid Prototyping Research Center, Department of Mechanical Engineering, Tsinghua University, Beijing, 100084, ChinaThe NiAl intermetallic layers and NiAl matrix composite layers with TiC particulate reinforcement were successfully synthesized by laser cladding with coaxial powder feeding of Ni/Al clad p...
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JLA Vol:16 Iss:3 (Laser-assisted chemical vapor deposition to directly write three-dimensional microstructures)
Authors:
S. I. Han
S. H. Jeong
Department of Mechatronics, Kwangju Institute of Science and Technology, 1 Oryongdong Pukgu, Kwangju 500-712, South KoreaApplication of laser-assisted chemical vapor deposition to the fabrication of three-dimensional microstructures is investigated. To fabricate a three-dimensional microstructure, a thin layer of deposit in desired patterns is first written on a flat substrate using the laser-direct-writing technique and on top of this layer a second layer is deposited to increase the height of the deposit pattern. After repeatedly depositing several layers in the same manner, a three-dimensional microstructure is fabricated. Optimum deposi...
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JLA Vol:16 Iss:3 (Methods for hazard assessment from viewing fiber optics with eye loupes)
Authors:
Wesley J. Marshall
U.S. Army Center for Health Promotion and Preventive Medicine, Aberdeen Proving Ground, Maryland 21010-5403
John Bell
Terabeam Corporation, Redmond, Washington
David H. Sliney
U.S. Army Center for Health Promotion and Preventive Medicine, Aberdeen Proving Ground, Maryland 21010-5403Current laser safety standards overestimate retinal hazards when viewing optical fiber tips with magnifying aids. Methods for assessing optical hazards are based on laser beam characteristics and assume worst-case exposure to both the unaided eye and when using a variety of optical aids. These standard methods provide overly conservati...
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JLA Vol:16 Iss:3 (Solidification model of laser cladding with wire feeding technique)
Authors:
Chien-Fu Hung
Jehnming Lin
Department of Mechanical Engineering, National Cheng Kung University, Tainan 701, TaiwanThe object of this study is to investigate the solidification problem in laser cladding with the wire feeding technique. The solidification phenomenon of laser cladding was analyzed by numerical simulation and experimental visualization. Good agreement has been obtained for 304 stainless steel wires cladding on round tubes and it transpires that there were three basic modes of clad profiles: thinning, thickening, and wavering of the clad thickness at different velocity settings between the feeding wire and the substrate in laser wire cladding. ©...
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