2pPAb14. Laser thermo-optical source of sound at a fractal surface in a liquid.

Session: Tuesday Afternoon, May 14

Time: 4:45

Author: Leonid M. Lyamshev
Location: N. N. Andreev Acoust. Inst., Shvernik Str. 4, 117036 Moscow, Russia
Author: M. L. Lyamshev
Location: Russian Acad. of Sciences, 117242 Moscow, Russia


Surfaces of real bodies are rough, uneven, or porous as a rule and are characterized by fractal properties. Surfaces may be fractal up to the molecular-level scale. Rough oceanic surface is also fractal. Laser photo-acoustic diagnostics of various media have been developing in recent years. It is based on laser excitation of sound (ultrasound or hypersound). Special features of laser sound excitation in a liquid half-space with the rough statistical fractal surface are investigated. It is assumed that an harmonically modulated laser beam is incident on the liquid surface. The height (amplitude) of surface waves is greater than the sound wavelength and the absorption length of light in the liquid. Fractal properties of the surface are characterized by the Weierstrass function and connected with it by a structural function. The Kirchhoff approximation is used to solve the boundary problem. The influence of fractal properties of the surface and parameters of laser radiation and liquid on the amplitude and spatial characteristics of intensity of the acoustic field excited in a liquid by laser radiation is analyzed.

from ASA 131st Meeting, Indianapolis, May 1996