Measurement of the velocity of laser induced acoustic wave in film using a fiber optic sensor

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Measurement of the velocity of laser induced acoustic wave in film using a fiber optic sensor

 

Author: Chau, Yuk-chuen
Title: Measurement of the velocity of laser induced acoustic wave in film using a fiber optic sensor
Degree: M.Sc.
Year: 1998
Subject: Acoustic surface wave devices
Optical fiber detectors
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Dept. of Applied Physics
Pages: 52 leaves : ill. (some col.) ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1463362
URI: http://theses.lib.polyu.edu.hk/handle/200/1411
Abstract: Mach-Zehnder fiber optic interferometer is used to measure the velocity of laser induced acoustic wave in films. The acoustic wave is generated by irradiation of a pulsed YAG laser focused onto the film surface with a cylindrical lens. The sensing arm of Mach-Zehnder interferometer is attached to the film at a know distance from the focus to pick up the acoustic signal. The laser pulse also provides an essential synchronizing trigger for a digital storage oscilloscope to measure the traveling time of the acoustic wave to the sensing arm. The acoustic wave velocity can be determined by the known distance and the traveling time. The elastic constants of the samples can then be deduced from the velocities. Pure copper and aluminum films are used to test the validity of the method. An industrial application is then explored to measure the elastic constants of magnetic tapes.

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