Self-focusing of ultrasound by random scattering objects in a liquid via parametric phase conjugation
Brysev A. P. , Bunkin F. V. , Krutyanskii L. M. , Preobrazhenskii V. L. , Pyl'nov Yu. V. , Stakhovskii A. D.
A self-focusing of sound by a stream of air bubbles in water has been realized experimentally and visualized by an optical method. The focusing occurs as the result of parametric phase conjugation in a solid. The active medium which is responsible for the phase conjugation of the ultrasound scattered by the bubbles is a NiFe204-based ferrite in the alternating magnetic field of a longitudinal pump. © 1995 American Institute of Physics.