JLA Vol:6 Iss:3 (High‐energy, long‐pulse, electron‐beam driven KrF laser in laser–matter interaction)
Authors:
J‐E. Montagne
Th. Sarnet
G. Inglesakis
M. Autric
Institute of Fluid Mechanics — Laser–Matter Interaction Group, Marseilles, FranceA high‐energy, long‐pulse, large‐volume, electron‐beam driven KrF laser was constructed in order to carry out laser–matter interaction experiments with metals, ceramics and polymers in the ultraviolet spectral range at 248 nm. This laser delivers up to 200 J in 400 ns. In the framework of applications such as machining or shock‐hardening, the knowledge of mechanical phenomena is very important in order to understand and maximize laser parameters. An ...
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JLA Vol:6 Iss:3 (Characterization of metal surfaces irradiated by a long‐pulse KrF excimer laser)
Authors:
Th. Sarnet
J. E. Montagne
G. Inglesakis
M. Autric
L. Barrallier
G. BarreauMetallic samples were irradiated by a long‐pulse (τ > 300 ns) KrF laser. The experiments were performed with an energy density of 0.3–120 J cm−2 and a power density of 1–400 MW cm−2. The samples investigated were pure aluminum, aluminum alloy, low‐alloy constructional steel and titanium alloy. They were polished to obtain a roughness of 10 < Ra < 0.08 μm and stress‐relief heat‐treated for some residual stress measurements. The characterization of th...
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JLA Vol:6 Iss:3 (Acoustic emission response of soda lime glass after a single Nd‐YAG laser pulse)
Authors:
R. Harrysson
P. Vomacka
Department of Engineering Materials, Luleå University of Technology, S‐951 87 Luleå, SwedenWhen machining brittle solids with a laser, crack formation can occur in the material around the irradiated area causing a strength reduction of the machined material. The purpose of this work was to study a well known brittle material (soda lime glass) by means of acoustic emission (AE) in order to investigate the correlation between visually observed crack formation and detected AE energy released by the crack formation in the material. During and after irradiation of soda lime glass with an Nd‐YAG laser pulse, the number...
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JLA Vol:6 Iss:3 (Safety concerns about laser pointers)
Authors:
David H. Sliney
Jerome E. DennisIn the past two years considerable concerns have been expressed about the safety of Class 3A laser pointers. The concern has been that Class 3A diode–laser pointers have replaced the safer helium–neon (He–Ne) Class 2 laser pointers. Hundreds of thousands of small He–Ne visible‐wavelength lasers have been traditionally used for alignment and pointing, laser demonstrations and laser displays in science, education and industry, but can the diode laser be as safe and effective? Not infrequently, some people associate “lasers” with Buck Rogers and “Star Wars”, and are concerned wh...
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JLA Vol:6 Iss:3 (Free electron laser irradiation at 200 μm inhibits DNA synthesis in living cells)
Authors:
Michael W. Berns
William Bewley
Chung‐Ho Sun
Pamela Templin
Alexander KarnThe effect of a 200 μm wavelength free electron laser (FEL) beam on vertebrate tissue culture cells in two study series is described. Cell cultures exhibited no morphological alterations. However, a statistically significant proportion of the cells exhibited a reduction in tritiated thymidine incorporation. The results suggest that this wavelength might affect DNA synthesis, and the studies demonstrate the feasibility of biological investigations with the FEL.
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JLA Vol:6 Iss:3 (Low‐level laser therapy (LLLT) and safety considerations)
Authors:
Myron L. Wolbarsht
Psychology Department, Duke University, Durham, NC 27706, U.S.A.Although the low‐power HeNe lasers and diode lasers used for low‐level laser therapy (LLLT) and photoactivation of biological processes are usually thought to be “safe”, the possibility that such lasers can cause biological effects raises the question of whether such laser action may, under some conditions, be adverse and thus be unsafe. Some research data can be interpreted as evidence for adverse effects. Laser safety standards classify all CW HeNe lasers with an output power below 1 mW as “Class 2,” as they are not considered a realistic hazard, whereas...
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JLA Vol:6 Iss:3 (Fast manipulation and modulation of laser beams with spinning devices)
Authors:
Gareth T. Williams
Physics Department, San Jose State University, San Jose, CA, U.S.A.Inexpensive battery‐operated motors can be used for a variety of safe, fast, laser beam‐steering and modulation activities, a number of which have been developed as part of the Laser Applications in Science Education (LASE) Project at San Jose State University. Those described here will be a laser stroboscope using a spinning slotted disc; a circular scanning system using a tilted rotating mirror, for bar‐code reading, investigating the focusing properties of lenses, lens aberrations and beam profiles; and a rotating polarizing sheet.
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JLA Vol:6 Iss:3 (Laser express: Putting together a laser‐based road show)
Authors:
Steven S. Lympany
Laser & Electro‐Optics Technology, Central Carolina Community College, Lillington, NC 27546, U.S.A.Laser technology has progressed to the point that most elementary through high school students are familiar with one or more laser applications. However, many of these students have not had the opportunity to witness a laser in acton where they can touch it and see it directly. In addition, most students are unaware of the career possibilities the field of laser technology has to offer. This paper presents the specifics of a successful laser‐based program that has been offered to K‐12 students and teachers in North Carolina over the la...
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JLA Vol:6 Iss:4 (Hazardous chemicals produced by laser materials processing)
Authors:
John M. Kokosa
GMI Engineering & Management Institute, Flint, MI, U.S.A.Despite evidence to the contrary, until recently many laser operators believed, or at least stated, that the only chemical by‐products of laser processing of any consequence were water and CO2. During the last eight years, especially, several investigations have shown that hazardous materials are produced when cutting or welding nearly all substrates. In the following paper, the major chemical hazards associated with processing metals, inorganics, biomaterials, and polymers are outlined.
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JLA Vol:6 Iss:4 (Laser accidents: Reviewing thirty years of incidents: what are the concerns — Old and new?)
Authors:
R. James Rockwell
Rockwell Laser Industries, PO Box 43010, Cincinnati, OH, U.S.A.Overall analysis reveals that laser accidents are generally caused by one or more of the following: unanticipated eye exposure during alignment; non‐use of available eye protection; equipment malfunction causing unwanted exposure; improper methods of handling high voltages, leading to severe shock or death; lack of protection for non‐beam hazards; improper restoration of equipment following service; and incorrect eyewear selection and/or eyewear failure, leading to unwanted exposure. The statistical laser information given in this review provides a starting point for more complete ...
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