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.

JLA Vol:14 Iss:4 (High-energy femtosecond pulsed laser micromachining of thin film deposited silicon in self-focused air medium)

Authors:
Yuanyuan Dong
Pal Molian
Department of Mechanical Engineering, Iowa State University, Ames, Iowa 50011

Christian Zorman
Mehran Mehregany
Department of Electrical Engineering and Computer Science, Case Western Reserve University, Cleveland, Ohio 44106

The ultrashort pulsed laser ablation of silicon wafers deposited with 1 μm thin film of SiC was performed in air medium using a 1 mJ, 120 fs, 800 nm Ti:sapphire laser, the objective being to determine the self-focusing capability of air to produce nanostructures. The effects of pulse energy, the number of pulses, pulse repetition rate and x–y translation speed on t...

JLA Vol:14 Iss:4 (Interaction of the keyhole and weld pool in laser keyhole welding)

Authors:
John Dowden
Department of Mathematics, University of Essex, Colchester, Essex CO4 3SQ, United Kingdom

There are several components to the motion of the liquid material in the weld pool in laser keyhole welding. Observations have shown not only that it moves in the plane perpendicular to the axis of the laser, but also that it moves parallel to the laser beam. It has been recognized for many years that the motion in the direction perpendicular to the surface of the work piece is important in connection with arc welding; it has, however, received less detailed study in connection with keyhole welding. The possible mechanisms are reviewed from a mathematical standpoint and Maran...

JLA Vol:14 Iss:4 (Penetration control in laser welding of sheet metal)

Authors:
S. Postma
Netherlands Institute for Metals Research (NIMR), P.O. Box 5008, 2600 GA, Delft, the Netherlands

R. G. K. M. Aarts
Johan Meijer
J. B. Jonker
Faculty of Engineering, University of Twente, P.O. Box 217, 7500 AE Enschede, the Netherlands

For economical reasons it is desirable to apply the highest possible speed during laser welding. Increasing the welding speed at a certain laser power might result in insufficient penetration of the weld. This work describes the design of a feedback controller, which is able to maintain full penetration in mild steel sheets. An optical detector, which is placed inside the Nd:Yttrium&ndash...

JLA Vol:14 Iss:4 (Process study for laser-induced surface coloration)

Authors:
H. Y. Zheng
G. C. Lim
X. C. Wang
J. L. Tan
Gintic Institute of Manufacturing Technology, 71 Nanyang Drive, Singapore 638075

James Hilfiker
J. A. Woollam Company, Inc., 645 M Street, Suite 102, Lincoln, Nebraska 68508

A KrF excimer laser beam is used to induce controllable and high-contrast colors on a stainless-steel surface under different processing conditions. The laser beam acts as a localized heating source that promotes the formation of semitransparent oxide films of varying thicknesses and morphologies on the sample surface. Ellipsometry and atomic force microscopy were employed to understand the laser-induce...

JLA Vol:14 Iss:4 (Surface characteristics and corrosion behavior of laser surface nitrided NiTi shape memory alloy for biomedical applications)

Authors:
H. C. Man
Z. D. Cui
T. M. Yue
Laser Processing Group, Advanced Manufacturing Technology Research Centre, Department of Industrial and Systems Engineering, The Hong Kong Polytechnic University, Kowloon, Hung hom, Hong Kong

Laser gas nitriding (LGN) has been applied to fabricate a TiN coating on the surface of NiTi alloy for the purpose of improving the surface properties. The microstructure, surface characteristics, and corrosion properties of the laser gas nitrided layer on NiTi alloy surface were investigated. The nickel release rate of the LGN specimen in Hanks’ solution was also investigated. The results of x-ray diffraction, x-ray photoelec...

JLA Vol:14 Iss:4 (The development and characteristics of a hand-held high power diode laser-based industrial tile grout removal and single-stage sealing system)

Authors:
J. Lawrence
Manufacturing Engineering Division, School of Mechanical and Production Engineering, Nanyang Technological University (NTU), Nanyang Avenue, Singapore 639798

K. Minami
M. J. J. Schmidt
L. Li
Laser Processing Research Centre, Manufacturing Division, Department of Mechanical Engineering, University of Manchester Institute of Science and Technology (UMIST), Manchester M60 1QD, United Kingdom

R. E. Edwards
A. W. Gale
Department of Civil and Construction Engineering, University of Manchester Institute of Science and Technology (UMIST), Manchester M60 1QD, United Kingdom

As the field of l...

JLA Vol:14 Iss:4 (Use of carbon dioxide (CO₂) laser radiation in exposure of implants (stage II): A metallography evaluation in dogs)

Authors:
Ma´rcia Vieira Marcondes Guimara˜es
Post Doctor Research Fellow, Department of Prosthesis, Sao Paulo State University–UNESP, School of Dentistry, Sao Jose dos Campos-SP, Brazil

Walter Niccoli-Filho
Head of Academic Group of Studies and Research with Laser in Dentistry, Sao Paulo State University–UNESP, School of Dentistry, Sao Jose dos Campos-SP, Brazil

Marco Antonio Bottino
Department of Prosthesis, Sao Paulo State University–UNESP, School of Dentistry, Sao Jose dos Campos-SP, Brazil

Carlos Schwab
Department of Physics at Advanced Studies Institute–IEAv, Lasers Division, Sao Jose dos Campos-S...

JLA Vol:14 Iss:4 (Visible and invisible laser radiation—problems in laser safety terminology)

Authors:
David H. Sliney
U.S. Army Center for Health Promotion and Preventive Medicine, Aberdeen Proving Grounds, Maryland 21010

David J. Lund
U.S. Army Medical Research Detachment, Brooks Air Force Base, Texas 78235

Wesley J. Marshall
U.S. Army Center for Health Promotion and Prevention Medicine, Aberdeen Proving Grounds, Maryland 21010

The spectral band between 400 and 700 nm is termed “visible” in laser safety standards, this is not the full extent of the visible spectrum. Light, or visible radiation, is that which is perceived by the human eye, and the spectral bandwidth for vision is really larger, extending into what some r...

JLA Vol:15 Iss:1 (Condition monitoring of laser systems: Monitoring the cover slide)

Authors:
H. K. To¨nshoff
A. Ostendorf
V. Kral
Laser Zentrum Hannover, Hollerithalle 8, 30419 Hannover, Germany

Laser systems are high investment production machines that require a high level of availability in order to be amortized. Laser condition monitoring methods can be used to avoid breakdowns and maintain a consistent quality. In particular elements such as the cover slide, which protect the focusing optics from getting splashed through the welding process, need to be monitored. The effects of dirt on the cover slide are detrimental to the beam quality reaching the workpiece and can cause a spontaneous failure of the cover slide. By using a laser ba...