JLA Vol:6 Iss:1 (Measurement of temperature and absorptance for laser processing applications)

Authors:
S. Ramanathan
M. F. Modest
Department of Mechanical Engineering, The Pennsylvania State University, University Park, PA 16802, U.S.A.

The use of CO₂ lasers has been successfully demonstrated for several manufacturing processes such as cutting, drilling, scribing, etc., of a wide range of materials. The absorptance of a material at the laser wavelength and at the material removal temperature substantially affect the efficiency of the laser machining process. Some materials have absorption bands in the mid‐infrared and the absorptance changes drastically with temperature at the CO₂ laser wavelength of 10.6 μm. Additionally, the absor...

JLA Vol:6 Iss:2 (Probability and risk in laser safety)

Authors:
Peter A. Smith
Special Senses Division, Royal Air Force Institute of Aviation Medicine, Farnborough, Hampshire GU14 6SZ, U.K.

International standards for the protection of the eyes from the hazards of laser radiation define a nominal ocular hazard distance (NOHD) beyond which an individual would not be expected to suffer any adverse effects from laser radiation. The NOHD assumes deliberate viewing of the laser source over an indefinite period of time and takes no account of the probability of the observer's eye being irradiated. This approach may lead to unrealistically large hazard areas for some laser devices. An alternative method of hazard assessment without compromising ...

JLA Vol:6 Iss:2 (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

The effect of the excimer laser on the surface of Ti–6Al–4V is reported. Particular concentration is given to surface modification for potential materials processing applications. Results showed that: (i) there is an optimum energy for smoothing titanium; (ii) at this energy density increasing the number of pulses has some, but not a significant, effect on the smoothing process; and (iii) relatively smooth surfaces could be achieved ...

JLA Vol:6 Iss:2 (CO₂ shielding gas effects in laser welding mild steel)

Authors:
D. H. Abbott
C. E. Albright

The most widely used shielding gases for laser welding of steels are helium and argon. Helium produces significantly more penetration than argon in penetration‐mode laser beam welding. Another gas that has been proposed as an alternative to these inert gases is carbon dioxide. The benefits of using carbon dioxide as a shielding gas for laser welding are that it costs less than helium and argon and that it provides nearly the same penetration as helium. The major drawback to its use as a shielding gas for mild steel is that it can cause porosity and other weld discontinuities. In this investigation helium and carbon dioxide were...

JLA Vol:6 Iss:2 (National Science Foundation undergraduate faculty enhancement workshop on advanced laboratory experiments using lasers)

Authors:
James E. Parks
Charles S. Feigerle
Robert Deserio
Joseph Wiest

A National Science Foundation undergraduate faculty enhancement workshop on advanced laboratory experiments using lasers was developed at the University of Tennessee, Knoxville, with the authors as the instructors. The workshop emphasized the development and implementation of laser‐based experiments primarily suitable for advanced undergraduate physics and chemistry laboratories. Participants gained practical, hands‐on experience in approximately 16 unique laser‐based experiments in atomic and molecular physics, physical chemistry, and biophysics. The wo...

JLA Vol:6 Iss:2 (Laser safety programs in general surgery)

Authors:
Raymond J. Lanzafame
University of Rochester and Laser Center, Rochester General Hospital, Rochester, NY, U.S.A.

General surgery represents a speciality where, while any procedure can be performed with lasers, there are no procedures for which the laser is the sine quo non. The general surgeon may perform a variety of procedures with a multitude of laser wavelengths and technologies. Laser safety in general surgery requires a multidisciplinary approach. Effective laser safety requires the oversight of the hospital's “laser usage committee” and “laser safety officer” while providing a workable framework for daily laser use in a variety of clini...

JLA Vol:6 Iss:2 (Proposal for a standard for laser plume filter technology)

Authors:
Douglas E. Ott
School of Engineering, Mercer University, Macon, Georgia, and Georgia BioMedical, Inc., Macon, Georgia, U.S.A.

A methodology to critically appraise and assess the efficiency and efficacy of filters used in smoke evacuation systems is proposed. Currently the methods for evaluation of laser smoke evacuation systems and filtering are fraught with inconsistency, and laced with innuendo and extraopolation. A variety of tissues including beef, chicken, pork, mouse and human have been described. Both carbon dioxide and ND:YAG lasers have been used. A wide range of power densities have been applied. Environmental conditions during the studies either have not been descr...

JLA Vol:6 Iss:1 (Standardization in the field of lasers in Europe—Towards common international standards)

Authors:
Ernst Sutter
Physikalisch‐Technische Bundesanstalt, Bundesallee 100, D‐38116 Braunschweig, Germany

Different standards in different European countries have given rise to technical trade barriers. The European Community made a great effort to establish a single market before the end of 1992 in which the free movement of goods is ensured. The first approach was to adopt directives setting up detailed requirements for all products. This has proved to be such a slow and difficult process that the New Approach has been adopted: the essential requirements are established by directives, whereas the technical specifications are detailed in harmonized standards....

JLA Vol:6 Iss:1 (Laser vibrometry on solid surfaces: The effects of laser speckle)

Authors:
S. J. Rothberg
N. A. Halliwell
Department of Mechanical Engineering, Loughborough University, Loughborough, Leicestershire LE11 3TU, U.K.

This letter discusses the phase and amplitude modulation of Doppler signals generated in laser Doppler velocimetry (LDV) systems with reference to the paper entitled ‘Dynamic laser Doppler velocimetry on solid surfaces’ by Rajadhyaksha and Stevenson (Vol. 4 No. 2). In particular, transit time and velocity gradient frequency broadenings are described in terms of the speckle pattern behavior on the photodetector and this approach is reconciled with the scattering element approach adopted by Rajadhyaksha and Stevenson....

JLA Vol:6 Iss:1 (Authors’ reply to the comments of Rothberg and Halliwell)

Authors:
M. M. Rajadhyaksha
W. H. Stevenson
Applied Optics Laboratory, School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47907, U.S.A.