JLA Vol:24 Iss:3 (2D longitudinal modeling of heat transfer and fluid flow during multilayered direct laser metal deposition process)

Authors:
Simon Morville
Muriel Carin
LIMATB, Universite´ de Bretagne-Sud/UEB, Centre de recherche Ch. Huygens, Rue de Saint Maude´, BP 92116, 56321 Lorient cedex, France

Patrice Peyre
Myriam Gharbi
PIMM, UMR 8006 CNRS-Arts et Me´tiers Paris Tech, 151 Boulevard de l’Hoˆpital, 75013 Paris, France

Denis Carron
Philippe Le Masson
LIMATB, Universite´ de Bretagne-Sud/UEB, Centre de recherche Ch. Huygens, Rue de Saint Maude´, BP 92116, 56321 Lorient cedex, France

Re´my Fabbro
PIMM, UMR 8006 CNRS-Arts et Me´tiers Paris Tech, 151 Boulevard de l’Ho&ci...

JLA Vol:6 Iss:4 (Holographic optical elements (HOEs): A serious application of holography)

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

Without disputing the excitement and sense of accomplishment associated with the production of display holograms, this paper suggests equal rewards from the production of holographic optical elements (HOEs). The elements described here are zone plates, diffraction gratings, interference filters and mirrors, and lenses. Ways of making each of these in an optics teaching laboratory are described, but the main emphasis will be on positive lens HOE.

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: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:7 Iss:1 (Development of laser finishing for non‐circular profiles)

Authors:
Ko‐Wang Liu
Paul S. Sheng
Department of Mechanical Engineering, University of California, Berkeley, CA 94720‐1740, U.S.A.

A laser‐based technique for finishing of non‐circular cylindrical parts is presented. In this process, the frequency characteristics of a desired non‐circular shape is extracted from a CAD through a Fast Fourier Transform algorithm and implemented through a CO₂ laser machining system. A galvanometer‐based scanner is used in the process to achieve programmable beam trajectories and high‐speed finishing. An error estimation scheme can be developed to determine the final dimensional erro...

JLA Vol:16 Iss:2 (High-power CO₂ laser design “from resonator end mirror to cutting lens focal point”)

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:9 Iss:3 (Experimental study of cutting thick aluminum and steel with a chemical oxygen–iodine laser using an N₂ or O₂ gas assist)

Authors:
David L. Carroll
James A. Rothenflue

A chemical oxygen–iodine laser (COIL) was used to cut aluminum and carbon steel. Cut depths of 20 mm in aluminum and 41 mm in carbon steel were obtained using an N₂ gas assist and 5–6 kW of power on target. The same laser at the same power level produced a cut depth of 65 mm in carbon steel with an O₂ gas assist; a low quality cut to a depth of nearly 100 mm in carbon steel was also demonstrated. These data are compared with existing COIL and CO₂ laser cutting data. COIL cuts carbon steel and stainless steel at approximately the same rate. For a given cut depth, power and spot size...

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:25 Iss:4 (Analysis of Yb:YAG thin disk laser resonator considering thermal lens effects: Experimentally and by Laser Cavity Analysis and Design)