Nonlinear acoustics of phase conjugate ultrasound beams
Résumé
Overview of nonlinear acoustics of phase conjugate waves (PCW) - the new domain of physical acoustics created by the participants of the Joint Russian-French laboratory LEMAC is presented. The original magneto-acoustic technique of supercritical parametricwave phase conjugation (WPC) is used as a basic method of generation of high intensity PCW. The results of experimental and theoretical studies of nonlinear propagation andinteraction of PCW in liquids are considered. Compensation of phase distortions and highquality retro-focusing of PCW in nonlinear and inhomogeneous media in conditions of break of time reversal invariance (TRI) are observed experimentally and describedtheoretically. Selective WPC of the harmonics of nonlinear beams and its application forharmonic imaging are demonstrated on an example of the nonlinear acoustic microscopy. Detection of nonlinear inhomogeneities by means of WPC is described. Low frequencywave generation by nonlinear interaction of high frequency PCW and its use forvelocimetry of scattering objects in liquid are discussed. Applications of TRI break forultrasonic WPC- imaging of flows and the advantages of nonlinear modes of flow imagingare demonstrated