JLA Vol:4 Iss:2 (Dynamic Laser Doppler Velocimetry on Solid Surfaces)

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

This paper presents the results of a detailed analytical and experimental investigation into the accuracy of a differential laser Doppler velocimeter (LDV) for dynamic, solid surface velocity measurements made over very short averaging times on the order of one millisecond. Accuracy limitations are derived, along with operating conditions and signal processing considerations needed to optimize LDV performance. An experiment is described which demonstrates the use of an LDV to instantaneously and accurate...

JLA Vol:18 Iss:1 (Three-dimensional analytical model on laser-powder interaction during laser cladding)

Authors:
Yan-Lu Huang
Jian Liu
Nai-Heng Ma
Jian-Guo Li
School of Materials Science and Engineering, Shanghai Jiaotong University, Shanghai, China 200030

To compute the attenuation of laser power by powder stream and the temperature distribution of the powder particles arriving at different sites on the surface of the workpiece, a three-dimensional analytical model was presented based on Lambert-Beer theorem, Mie’s theory, and heat equilibrium principle. The obtained results revealed that for a given stream spread and speed of powder particles, the laser intensity distribution of laser spot and the temperature distribution of the powder part...

JLA Vol:24 Iss:5 (The numerical analysis and measurements of temperature profile in fat tissue during neodymium-doped yttrium aluminum garnet laser irradiation for laser-assisted lipolysis)

Authors:
Jong-In Youn
Department of Biomedical Engineering, College of Medical Science, Catholic University of Daegu, Hayangeup, Gyongsansi, Gyongbuk 712-702, South Korea

The purpose of the study is to investigate the temperature profile of fat tissue during neodymium-doped yttrium aluminum garnet laser irradiation (1064, 1320, and 1444 nm wavelengths) for laser-assisted lipolysis. The numerical analysis was performed to assess the wavelength dependence of the temperature distribution in fat tissue. For the internal temperature profile measurements, a cannula was placed in the middle of fat tissue for laser irradiation, and two hypodermic thermocouple needles were placed at 2 and 5 mm...

JLA Vol:23 Iss:3 (Parameter optimization of a laser-induced fluorescence system for <em>in vivo</em> screening of oral cancer)

Authors:
V. K. Unnikrishnan
Rajesh Nayak
Rodney Bernard
Centre for Atomic and Molecular Physics, Manipal University, Manipal, 576 104, India

K. Jeena Priya
Department of Oral Medicine and Radiology, MCODS Mangalore, Manipal University, Manipal, 575 001, India

Ajeetkumar Patil
Centre for Atomic and Molecular Physics, Manipal University, Manipal, 576 104 India

J. Ebenezer
PG & Research Department of Physics, Jamal Mohamed College, Tiruchinapalli, Manipal, 620 020, India

Keerthilatha M. Pai
Department of Oral Medicine and Radiology, MCODS Manipal, Manipal University, Manipal,576 104 India<...>

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&hyphen;infrared and the absorptance changes drastically with temperature at the CO₂ laser wavelength of 10.6 μm. Additionally, the absor...

JLA Vol:16 Iss:2 (High-power CO₂ laser design &ldquo;from resonator end mirror to cutting lens focal point&rdquo;)

Authors:
David Toebaert
HACO NV, Oekenestraat 120, 8800 Rumbeke, Belgium

Wybo Wagenaar
Infinite Simulation Systems BV, Lange Bunder 3, 4854 MB Bavel, Netherlands

An algorithm is derived that allows calculating all optical parameters relevant to the design of a high-power CO₂ laser, taking into account the practical needs of a flying-optics type of laser cutting machine. The novelty of the approach taken is that the resonator and the beam delivery optics are treated simultaneously, which allows for greater flexibility in design. To begin with, the often-used optical configuration of a stable resonator combined with a beam expander for collimation is mod...

JLA Vol:20 Iss:3 (Investigation of femtosecond laser induced thermal ablation of polyethylene)

Authors:
Andrew J. Lee
Judith M. Dawes
Michael J. Withford
Centre of Ultrahigh-bandwidth Devices for Optical Systems (CUDOS) and MQPhotonics Research Centre, Department of Physics, Macquarie University, 2109 NSW, Australia

We present a novel method for profiling high aspect ratio and undercut laser drilled holes using sacrificial layers. This profiling method is used to compare and contrast laser ablation of polyethylene films under exposure to ultraviolet (266 nm) and near-infrared (800 nm) radiation from an ultrafast, femtosecond laser. We find that ultraviolet femtosecond pulsed laser processing of this polymer exhibits similar characteristics to...

JLA Vol:8 Iss:2 (Laser materials processing at Sandia National Laboratories)

Authors:
James L. Jellison
Michael J. Cieslak
Sandia National Laboratories, Albuquerque, NM 87185, U.S.A.

This paper describes the laser materials processing capabilities at Sandia National Laboratories. Some of the advances in the understanding of various aspects of laser materials processing which have been made by the laser materials processing team at Sandia are discussed.

JLA Vol:3 Iss:1 (Nursing Perspective: Clinical Laser Safety Issues Survey)

Authors:
Penny J. Smalley
Laser Resources & Consulting Services, Chicago, Illinois

JLA Vol:14 Iss:3 (Pulsed laser driven deposition of spattered molten particles and its application to the manufacturing of wear-resistant coatings)

Authors:
Toru Nagai
Takashi Inoue
Applied Laser Engineering Research Institute, 2085-16 Uenoyama, Fukasawa, Nagaoka 940-2135, Japan

Hirofumi Shimura
Mechanical Engineering Laboratory, Agency of Industrial Science and Technology, 1-2 Namiki, Tsukuba 305-8564, Japan

In this article, we report on a new process for manufacturing metal coatings with submillimeter thickness by pulsed laser driven deposition of molten metal particles. The process of “laser spattering of molten particles” using a high pulse-energy laser is considered to be effective compared to the conventional physical vapor process based on vaporized ultrafine particle generati...