Vibration modal analysis using all-optical photorefractive processing

Thomas Chatters Hale; Kenneth L. Telschow

doi:10.1117/12.255496

25 October 1996 Vibration modal analysis using all-optical photorefractive processing

Thomas Chatters Hale, Kenneth L. Telschow

Proceedings Volume 2849, Photorefractive Fiber and Crystal Devices: Materials, Optical Properties, and Applications II; (1996) https://doi.org/10.1117/12.255496
Event: SPIE's 1996 International Symposium on Optical Science, Engineering, and Instrumentation, 1996, Denver, CO, United States

Abstract

A new experimental method for vibration modal analysis based on all-optical photorefractive processing is presented. The method utilizes an optical lock-in approach to measure phase variations in light scattered from optically rough, continuously vibrating surfaces. In this four-wave mixing technique, all-optical processing refers to mixing the object beam containing the frequency modulation due to vibration with a single frequency modulated pump beam in the photorefractive medium that processes the modulated signals. This allows for simple detection of the conjugate wavefront image at a CCD. The conjugate intensity is shown to be a function of the first-order ordinary Bessel function and linearly dependent on the vibration displacement induced phase (delta) , for (delta) equals 4(pi) (xi) /(lambda) << 1 where (xi) is the vibration displacement and (lambda) is the source wavelength. Furthermore, the results demonstrate the unique capabilities of the optical lock-in vibration detection technique to measure vibration signals with very narrow bandwidth (< 1 Hz) and high displacement sensitivity (sub-Angstrom). This narrow bandwidth detection can be achieved over a wide frequency range from the photorefractive response limit to the reciprocal of the photoinduced carrier recombination time. The technique is applied to determine the modal characteristics of a rigidly clamped circular disc from 10 kHz to 100 kHz.

Citation Download Citation

Thomas Chatters Hale and Kenneth L. Telschow "Vibration modal analysis using all-optical photorefractive processing", Proc. SPIE 2849, Photorefractive Fiber and Crystal Devices: Materials, Optical Properties, and Applications II, (25 October 1996); https://doi.org/10.1117/12.255496

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