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Proceedings Paper

Silicon-on-insulator photoconductors for noncontact ultrasound vibration measurement using laser speckle
Author(s): Jonathan Bessette; Elsa Garmire
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Paper Abstract

The motion of a vibrating specular surface can be measured by monitoring the change in speckle pattern of a reflected laser beam. Smaller speckles allow for a more sensitive measurement, but provide a weaker signal when monitored with a correspondingly sized photodiode. The signal of a photoconductor, on the other hand, scales with the ratio of its dimensions, and so can be resized without loss of signal. Here we present a prototype detector made from micron-scale, isolated mesas of intrinsic silicon, fabricated lithographically from a commercial silicon-on-insulator wafer. The prototype has a frequency response extending into the megahertz regime, making it suitable for ultrasound testing applications. Only a single laser beam, with no separate interferometer or optical reference, is required for displacement measurement with laser speckle monitoring, so such a system provides a robust and simple alternative to other optical detection methods. Initial tests have captured ultrasound Lamb wave vibrations and standing waves induced by optical excitation in thin copper and aluminum strips.

Paper Details

Date Published: 4 August 2009
PDF: 8 pages
Proc. SPIE 7386, Photonics North 2009, 73861L (4 August 2009); doi: 10.1117/12.839623
Show Author Affiliations
Jonathan Bessette, Dartmouth College (United States)
Elsa Garmire, Dartmouth College (United States)

Published in SPIE Proceedings Vol. 7386:
Photonics North 2009
Réal Vallée, Editor(s)

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