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.

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 Karn

The 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.

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, France

A 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 ...

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...

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...

JLA Vol:6 Iss:3 (Safety concerns about laser pointers)

Authors:
David H. Sliney
Jerome E. Dennis

In 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...

JLA Vol:6 Iss:4 (Characteristics of power meters for high power CO₂ lasers)

Authors:
Keng H. Leong
Donna J. Holdridge
Kenneth R. Sabo
Laser Applications Laboratory, Technology Development, Argonne National Laboratory, University of Chicago, IL 60439, U.S.A.

Four different instruments used for measuring CO₂ laser beam power in the kilowatt range were evaluated. The techniques used to determine the laser beam power included temperature increase from an absorber of known mass and specific heat, temperature increase from a steady flow of water used to cool the absorber, thermal gradient caused by edge‐cooling a circular absorber, and diffuse scattering from a small portion of the water‐cooled absorber surface. Th...

JLA Vol:6 Iss:4 (Effect of the helium–neon laser on the healing of extraction wounds: A histological study in rats)

Authors:
Walter Niccoli‐Filho
Tetuo Okamoto

A histological study on the healing of extraction wounds following laser irradiation using a He–Ne laser, was carried out in rats. The results suggest that this mode of treatment has a beneficial effect on initial bony wound healing. Proliferation of fibroblasts and formation of trabecular osteoid tissue were found to be more prominent within the irradiated group. The deposition of led in the newly formed bone suggests swifter ossification within the irradiated group.

JLA Vol:6 Iss:4 (Effective laser applications in high school physics)

Authors:
Jeff Sweet
North Salinas High School Salinas, CA 93906, U.S.A.

Laser light is an instant attention‐getter in the classroom; thus any activity which uses the laser as an instructional tool is sure to enhance student motivation. This paper discusses two demonstrations and one experiment involving laser applications that the author has found to be particularly beneficial in terms of (1) instructional effectiveness and (2) arousing the interest of high school physics students. Brief descriptions follow. Refraction through lenses can be nicely illustrated by splitting laser light into several parallel beams and directing them through a fish tank filled with a scatt...

JLA Vol:6 Iss:4 (Erratum: Excimer laser processing of Ti–6Al–4V)

Authors:
J. A. Folkes
K. Shibata
Nissan Motor Co. Ltd, Materials Research Laboratory, Central Engineering Laboratories, 1, Nasushima‐cho, Yokosuka 237, Japan