JLA Vol:5 Iss:2 (Characterization of Laser Produced High Molybdenum Surface Alloys on Stainless Steel Substrates)

Authors:
Dilip Kumar
K. Sridhar
A. R. Biswas
G. L. Goswami
M. B. Deshmukh

High Mo surface alloys on stainless steels 304L and 316L were produced by laser surface alloying. For this, a layer of 60 μm thickness was overlaid on the substrates by plasma spraying of Mo powders. These were further treated by a Nd:YAG pulsed laser for alloying. Depths of alloying in the range of 440–1110 μm were achieved. Concentration in the range of 5.2–15.0 wt% Mo within the laser alloyed zone was, in general, uniform throughout. During alloying, in‐situ heating at 700°C was required to prevent cracking in samples wi...

JLA Vol:5 Iss:2 (Experimental Method for Determining the Coherence Length of CW Lasers Using a Michelson Interferometer)

Authors:
Sami Alaruri
Allison Gas Turbine Division, General Motors Corporation, Sensor Development Group

Theoretical analysis of the relationship between coherence length and the resonant‐longitudinal modes in an optical cavity is given. A Michelson interferometer is used to measure the coherence lengths of two CW He‐Ne laser cavities. Analysis of the experimental measurements shows good agreement with the theoretically predicted values.

JLA Vol:5 Iss:2 (Tutorial Guide: Laser Measurement Techniques Guide For Hazard Evaluation. Part 2)

Authors:
Terry Lyon
Laser Microwave Division, U.S. Army Environmental Hygiene Agency

A tutorial guide is presented to provide uniform guidance when performing radiometric measurements upon laser systems to perform a hazard evaluation. This guide was requested by and presented to the Department of Defense (DOD) Laser System Safety Working Group (LSSWG) to serve as a standardized method when performing hazard evaluations primarily upon tactical and training military laser systems including laser rangefinders and designators. Technical information is provided in detail to select a suitable detector, preform radiometric measurements, assess laser system pointing errors, calculate laser p...

JLA Vol:5 Iss:2 (Laser Light Scattering in Biomedical Diagnostics and Therapy)

Authors:
Valery V. Tuchin
Chernyshevsky Saratov State University, Astrakhanskaya 83, 410071 Saratov, Russia

The description of special features of laser light interaction with biotissues, such as the skin, eye and dental tissues etc., with respect to laser diagnostics and therapy methods development is done. Optical models of transparent and turbid biotissues are analyzed. The role of static and dynamic light scattering in the light dosimetry, tissue heating, and receiving information of biotissue optical parameters, its structure, movements, and vibrations is considered.

JLA Vol:5 Iss:2 (Some Military Conversion Projects for Biomedical Applications)

Authors:
James H. Kerr
Leon Goldman
Departments of Dermatology and Clinical Investigation, Naval Hospital, San Diego, California

JLA Vol:5 Iss:1 (Single Pass Laser Cutting of Polymers)

Authors:
R. Patel
G. Baisch
IBM Corporation, GTD, Hopewell Junction, New York

Since the early 1980's discovery of the ability of excimer lasers to etch polymers precisely and cleanly with minimal thermal damage, excimer lasers have been used actively in the semiconductor industry for various manufacturing processes. In the present study a process for laser cutting of polymers has been investigated. A laser beam of controlled cross‐sectional shape is imaged onto a polymer surface. The geometry of the cutting path is controlled by precise movement of a sample mounted on a 2‐axis computer controlled work stage. This type of a process is useful for applications ...

JLA Vol:5 Iss:1 (Heat Flow in Laser Die Blank Welding)

Authors:
Y.‐S. Yang
C. R. Hsu
C. E. Albright
Y. Kuroda

Laser welded die blanks are finding increased usage in many industrial applications. This investigation was undertaken to establish a simplified means of calculating thermal cycles experienced in the fusion and heat affected zones on laser welds typically used in die blank welding. A planar solution domain perpendicular to the direction of travel was selected to simplify the finite element calculations. The resulting calculation technique provided reasonably accurate prediction of the thermal cycles measured by Moon and Metzbower, and the size of fusion zones and heat affected zones o...

JLA Vol:5 Iss:1 (LASER CUTTING OF STEELS: A physical and chemical analysis of the particles ejected during cutting. Part II)

Authors:
J. Powell
A. Ivarson
C. Magnusson

This paper is a continuation of work published in an earlier edition of this journal[1]. Both papers deal with the results of a detailed analysis of the particles ejected from the cut zone during laser cutting of mild and stainless steels. Reference 1 presented the thermochemical data and discussion generated by the experimental investigation. This paper concentrates on the physical characteristics and metallography of the particles. Analysis techniques used included: Scanning Electron Microscopy, optical microscopy, metallography and particle sizing. The results from this extensive analysis have enabled the authors...

JLA Vol:5 Iss:1 (Prediction Of Cavity Shape And Material Removal Rates Using A Two Dimensional Axisymmetric Heat Conduction Model For Fibrous Ceramic Insulation And Comparison With Experiments)

Authors:
Mingli He
P. J. Bishop
A. Minardi
University of Central Florida

High power lasers are used in industry as machining tools for many operations including drilling, cutting, welding, and etching. Because of its advantages over conventional machining such as tight tolerances, ability to machine hard materials without wearing of the machine tool, and ease of automation, an experimental and analytical study was undertaken to investigate the feasibility of the laser to cut a nearly pure fibrous ceramic used as insulation material on the Space Shuttle. An analytical model was developed for drilling using a spatially varying laser beam. The model was used to ...

JLA Vol:5 Iss:1 (The Protective Characteristics of Polycarbonate Lenses Against CO₂ Laser Radiation)

Authors:
David H. Sliney
Shawn D. Sparks
Rodney L. Wood
Laser Microwave Division, U.S. Army Environmental Hygiene Agency, Aberdeen Proving Ground, Maryland

The vulnerability of plastic laser eye protection used with Class 4 CW lasers was studied using a high‐power industrial laser to produce 4 by 4 cm burn zones. Since a CW (or repetitively pulsed) laser beam can burn through such eye protectors, this potential is of concern to Laser Safety Officers (LSOs) prescribing laser eye protectors and transparent barriers for use around both the 10 to 80‐W CO₂ lasers used in surgery as well as multi‐kilowatt industrial CO₂ la...