Detection of the Transient Motion of a Scattering Surface by Two-Wave Mixing in a Photorefractive Crystal,
Abstract
Optical detection of the transient surface motion of objects is an area of far reaching practical importance. Applications Include the vibration monitoring of many engineering structures (power plants, aircrafts, engines of various kinds ... ) and more recently the detection of ultrasound produced by pulse laser excitation. This technique, now in active development in our laboratory and elsewhere, extends ultrasonic inspection of materials to conditions otherwise difficult or impossible (complex geometries, hot products on a production line ... ). Various optical systems have been devised for detecting surface motion have been recently reviewed. We are reporting here the novel use of two wave mixing in a photorefractive crystal for detecting such a motion and in particular ultrasonic displacement produced by pulsed laser excitation. This approach has the merit of being applicable to a rough surface by integrating over many speckles and of having a very broad frequency detection bandwidth. The use of two-wave mixing for coherent homodyne detection of arbitrary wavefronts was previously reported and applied to detection and amplification of an intensity modulated wave.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 22, 1992
- Accession Number
- ADP006788
Entities
People
- J. -p. Monchalin
- R. K. Ing