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 GroupTheoretical 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.
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JLA Vol:14 Iss:4 (High-energy femtosecond pulsed laser micromachining of thin film deposited silicon in self-focused air medium)
Authors:
Yuanyuan Dong
Pal Molian
Department of Mechanical Engineering, Iowa State University, Ames, Iowa 50011
Christian Zorman
Mehran Mehregany
Department of Electrical Engineering and Computer Science, Case Western Reserve University, Cleveland, Ohio 44106The ultrashort pulsed laser ablation of silicon wafers deposited with 1 μm thin film of SiC was performed in air medium using a 1 mJ, 120 fs, 800 nm Ti:sapphire laser, the objective being to determine the self-focusing capability of air to produce nanostructures. The effects of pulse energy, the number of pulses, pulse repetition rate and x–y translation speed on t...
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JLA Vol:18 Iss:4 (Threshold powers and delays for igniting propane and butane-air mixtures by cw laser-heated small particles)
Authors:
Thomas H. Dubaniewicz
National Institute for Occupational Safety and Health, Pittsburgh Research Laboratory, 626 Cochrans Mill Road, Pittsburgh, Pennsylvania 15236The National Institute for Occupational Safety and Health, Pittsburgh Research Laboratory conducted a study of laser safety in potentially flammable environments. Researchers measured threshold igniting powers as a function of beam diameter for butane and propane-air mixtures by laser-heating targets placed on optical fiber tips using a 1064 nm laser. The minimum igniting powers for propane-air and butane-air were about 250 and 300 mW, respectively. Threshold igniting powers for propane-air were approxima...
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JLA Vol:22 Iss:4 (A fast method for morphological analysis of laser drilling holes)
Authors:
M. Schneider
L. Berthe
M. Muller
R. Fabbro
Laboratoire PIMM (CNRS) ARTS et METIERS ParisTech, 151 Boulevard de l’Hopital, 75013 Paris, FranceThis paper presents an original method for analyzing laser drilled holes. The so-called Direct Observation of Drilled hOle (DODO) method is introduced and its applications. The hole characterization that’s been made is compared with x-ray radiography and cross-section analysis. Direct Observation of Drilled hole provides instantaneously surface state, geometric shape, as well as recast layer structure, without additional operation. Since no mounting resin is used to embed the sample, th...
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JLA Vol:7 Iss:1 (Taking advantage of laser properties to enhance demonstrations and student laboratories)
Authors:
Michele L. Brill
Camden County College—Physics/Lasers, Box 200, Blackwood, NJ 08012, U.S.A.This paper reflects the proceedings of a workshop for local educators provided by Camden County College Laser Curriculum faculty which addressed the question: ‘How can the teacher take advantage of laser properties to improve or enhance demonstrations and student labs?’ Explored here are illustrative ways in which to utilize, for educational purposes, the three well‐known characteristics of lasers: monochromaticity, directionality, and coherence. There is a faculty overlap between the Physics Department and the Laser Curriculum faculty at the college. The use o...
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JLA Vol:17 Iss:2 (Feedback control effects on dimensions and defects of H13 tool steel by direct metal deposition process)
Authors:
Y. Hua
J. Choi
Department of Mechanical and Aerospace Engineering and Engineering Mechanics, University of Missouri, Rolla, Missouri 65409-1060As a promising and novel manufacturing technology, laser aided direct metal deposition (DMD) process produces near-net-shape functional metal parts directly from the computer aided design (CAD) model. In-process feedback control has been recognized as a critical element to ensure the dimensional accuracy as well as near-net-shape production. Furthermore, process parameters should be delicately controlled to produce defect-free parts with superior mechanical properties. A closed loop real-time optical height control system...
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JLA Vol:21 Iss:4 (Numerical model of a laser-sustained argon plasma)
Authors:
R. Akarapu
A. R. Nassar
Department of Engineering Science and Mechanics, Penn State University, University Park, Pennsylvania 16802-6812
S. M. Copley
Applied Research Laboratory and Department of Mechanical and Nuclear Engineering, Penn State University, University Park, Pennsylvania 16802-6812
J. A. Todd
Department of Engineering Science and Mechanics, Penn State University, University Park, Pennsylvania 16802-6812A steady state axi-symmetric model was developed to predict the size, shape and temperature of a laser-sustained plasma in flowing argon. The power of the carbon dioxide (CO2) laser and the free s...
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JLA Vol:15 Iss:2 (Plasma assisted laser surface alloying)
Authors:
M. H. McCay
C. M. Sharp
J. A. Hopkins
The Center for Laser Applications, The University of Tennessee Space Institute, Tullahoma, Tennessee 37388
B. Szapiro
The Department of Physics, University of the South, Sewanee, Tennessee
T. D. McCay
The Center for Laser Applications, The University of Tennessee Space Institute, Tullahoma, Tennessee 37388The combination of plasma arc with a Nd:YAG laser during surface alloying produces a synergistic effect which significantly increases the depth of the melt pool beyond that expected by a summation of the individual depths. Incremental increases in laser power produce ...
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JLA Vol:19 Iss:3 (Femtosecond pulsed laser microfabrication of SiC MEMS microgripper)
Authors:
Monica Vendan
Pal Molian
Mechanical Engineering Department, Iowa State University, Ames, Iowa 50011We report the capability of an ultrafast laser to pattern an electrostatic-comb-drive microgripper in the chemically difficult-to-etch 3C-SiC thin films. A microgripper with overall dimensions 1.2 mm×0.35 mm and a gap of 20 μm was designed and fabricated for the purpose of grasping and transporting microscale objects in hostile and harsh environments. Atmospheric pressure chemical vapor deposition was used to deposit thin films (∼2 μm) of 3C-SiC on 〈100〉 silicon substrates. A Ti:sapphire laser with 120 fs pulse wid...
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JLA Vol:23 Iss:2 (Microcomputed tomography analysis of intralayer porosity generation in laser direct metal deposition and its causes)
Authors:
M. Naveed Ahsan
Laser Processing Research Centre, School of Mechanical, Aerospace and Civil Engineering, University of Manchester, Sackville Street, Manchester M13 9PL, United Kingdom
Robert Bradley
Henry Moseley X-ray Imaging Facility, School of Materials, University of Manchester, Grosvenor Street, Manchester M13 9PL, United Kingdom
Andrew J. Pinkerton
Laser Processing Research Centre, School of Mechanical, Aerospace and Civil Engineering, University of Manchester, Sackville Street, Manchester M13 9PL, United KingdomLaser direct metal deposition has wide application in the areas of rapid manufacturing, surface coating, and compon...
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