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Proceedings Paper

Heterodyne laser-Doppler vibrometer with a slow-shear-mode Bragg cell for vibration measurements up to 1.2 GHz
Author(s): Christian Rembe; Sebastian Boedecker; Alexander Dräbenstedt; Fred Pudewills; Georg Siegmund
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Paper Abstract

Several new applications for optical ultra-high frequency (UHF) measurements have been evolved during the last decade by advancements in ultra-sonic filters and actuators as well as by the progress in micro- and nanotechnology. These new applications require new testing methods. Laser-based, non-influencing optical testing is the best choice. In this paper we present a laser-Doppler vibrometer for vibration measurements at frequencies up to 1.2 GHz. The frequency-shifter in the heterodyne interferometer is a slow-shear-mode Bragg cell. The light source in the interferometer is a green DPSS (diode pumped solid state) laser. At this wavelength the highest possible frequency shift between zero and first diffraction order is a few MHz above 300 MHz for a slow shear-mode Bragg cell and, therefore, the highest possible bandwidth of the laser-Doppler vibrometer should usually be around 300 MHz. A new optical arrangement and a novel signal processing of the digitized photo-detector signal is employed to expand the bandwidth to 1.2 GHz. We describe the utilized techniques and present the characterization of the new ultra-high-frequency (UHF) vibrometer. An example measurement on a surface acoustic wave (SAW) resonator oscillating at 262 MHz is also demonstrated. The light-power of the measurement beam can be switched on rapidly by a trigger signal to avoid thermal influences on the sample.

Paper Details

Date Published: 17 June 2008
PDF: 12 pages
Proc. SPIE 7098, Eighth International Conference on Vibration Measurements by Laser Techniques: Advances and Applications, 70980A (17 June 2008); doi: 10.1117/12.802930
Show Author Affiliations
Christian Rembe, Polytec GmbH (Germany)
Sebastian Boedecker, Polytec GmbH (Germany)
Alexander Dräbenstedt, Polytec GmbH (Germany)
Fred Pudewills, Polytec GmbH (Germany)
Georg Siegmund, Polytec GmbH (Germany)

Published in SPIE Proceedings Vol. 7098:
Eighth International Conference on Vibration Measurements by Laser Techniques: Advances and Applications
Enrico Primo Tomasini, Editor(s)

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