JLA Vol:7 Iss:4 (Laser applications in science education (LASE) Project: an introduction to photonics at the secondary school level)

Authors:
Gareth T. Williams
Physics Department, San Jose State University, San Jose, California, U.S.A.

JLA Vol:7 Iss:4 (Laser Applications in Science Education (LASE) Project at Santa Teresa High School)

Authors:
James D. Sagray
Science Department, Santa Teresa High School, San Jose, California 95123, U.S.A.

The goal of the Laser Applications in Science Education (LASE) Project, centered at San Jose State University, is to bring significant laser technology and optics to the secondary level with a special emphasis on student research and publication. Its implementation at Santa Teresa High School has focused on permitting all students in physics classes (32/period) to experience laser labs in small groups working throughout the classroom. In addition to receiving this exposure, all physics students are encouraged to do original research projects and to compete for cash or other prize...

JLA Vol:6 Iss:1 (Laser safety notes)

Authors:
Robert Weiner
Weiner Associates, Manhattan Beach, California U.S.A.

JLA Vol:6 Iss:1 (Effects of process parameters on the fatigue strength of laser beam welds)

Authors:
P. C. Wang
K. M. Ewing

An experimental study, augmented by three‐dimensional finite element analysis, was performed to assess the effects of various process parameters such as presence of galvanized coating, welding speed and weld geometry (weld start and stop, metal fit‐up, and weld orientation) on the fatigue resistance of laser beam welds. It was found that the fatigue resistance of laser beam welds depends upon the welding speed used and weld geometry. With a 2.75 kW CO₂ laser and at a welding speed of 38.1 mm s⁻¹, the resultant laser beam welds gave the highest fatigue resistance. For a continuous weld, maintaining ...

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:1 (Mass transport during laser welding of stainless steels and alloys used by US Navy)

Authors:
Anand J. Paul
Parwaiz A. A. Khan
Manufacturing and Materials Division, Concurrent Technologies Corporation, 1450 Scalp Avenue, Johnstown, PA 15904, U.S.A.

Lasers, though developed only about a quarter century ago, are now being routinely used in the automotive, aerospace and other industries to produce superior quality, high‐speed autogenous welds with narrow heat‐affected zones in a number of alloys. However, they cannot at present be used to successfully weld certain important structural alloys due to a change in weld composition resulting from selective mass transport of certain alloying elements from the laser‐melted region. The loss of a...

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.

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 (Amending the CDRH performance standard for laser products)

Authors:
Jerome E. Dennis
Office of Compliance and Surveillance Center for Devices and Radiological Heath, US Food and Drug Administration, Silver Springs, MD, U.S.A.

The most recent amendments to the Federal performance standard for laser products became effective in 1985 and 1986. At this time, the Center for Devices and Radiological Health (CDRH) is making public its intention to amend the standard again and is inviting suggestions and comments. The amendments that are now under consideration are based upon advances in the sciences of photobiology and hazard evaluation. They are also intended to harmonize with developments in international standards for similar products, and to cla...