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Proceedings Paper

Measurement of laser-induced acoustic wave in films using fiber optic sensor
Author(s): K. S. Lau; K. H. Wong; Y. W. Wong; Tommy H.T. Chan
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Paper Abstract

The sensitivity, flexibility, compactness and lightness of an optical fiber are utilized to monitor the acoustic waves propagating in a film. In this work, the wave is initiated by the irradiation of a pulsed Nd--YAG laser line focused onto the film surface through a cylindrical lens. The sensing arm of a Mach-Zehnder fiber optic interferometer sensor is attached to the film at a known distance from the focus to pick up the acoustic signal. The laser pulse also provides the essential synchronizing trigger to measure the arrival time of the acoustic wave. The speed of the wave through the film can be evaluated from the wave propagation time and the position of attachment of the sensing fiber. The modulus of the film can then be deduced from the speed of the wave. The sensor is stabilized against thermo-drift with a thermal feed back circuit and enhanced in visibility with a polarization controller. The moduli of several metal, polymer and diamond- like carbon films have been obtained by this method.

Paper Details

Date Published: 20 March 1997
PDF: 5 pages
Proc. SPIE 2921, International Conference on Experimental Mechanics: Advances and Applications, (20 March 1997); doi: 10.1117/12.269846
Show Author Affiliations
K. S. Lau, Hong Kong Polytechnic Univ. (Hong Kong)
K. H. Wong, Hong Kong Polytechnic Univ. (Hong Kong)
Y. W. Wong, Hong Kong Polytechnic Univ. (Hong Kong)
Tommy H.T. Chan, Hong Kong Polytechnic Univ. (Hong Kong)


Published in SPIE Proceedings Vol. 2921:
International Conference on Experimental Mechanics: Advances and Applications
Fook Siong Chau; C. T. Lim, Editor(s)

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