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Abstract (Invited) |
Supercritical Parametric Phase
Conjugation of Ultrasound Waves. Application in Nonlinear Acoustic Imaging
P.Pernod (Institut d'Electronique et de
Micro-electronique du Nord (IEMN-DOAE-UMR CNRS 8520), Ecole Centrale de Lille,
Villeneuve d'Acsq, France); V.Preobrazhensky (Institut d'Electronique et de
Micro-electronique du Nord (IEMN-DOAE-UMR CNRS 8520), Ecole Centrale de Lille,
Villeneuve d'Acsq, France, and Wave Research Center of General Physics
Institute RAS, Moscow, Russia); F.Bunkin, A.Brysev, L.Krutyansky (Wave Research
Center of General Physics Institute RAS, Moscow, Russia)
e-mail:
philippe.pernod@iemn.univ-lille1.fr
Parametric
wave phase conjugation (WPC) is a new tool for ultrasonic engineering providing
time reversal transformation of acoustic beams with giant amplification [1].
Application of parametric WPC for compensation of phase distortions in linear
acoustic imaging was already demonstrated. Possibility to combine parametric
amplification and phase conjugation of ultrasound is interesting for various
applications in nonlinear acoustics. In the present paper the results of
experimental and theoretical studies of WPC-retrofocusing for nonlinear
acoustic imaging are reviewed. Generally speaking, amplification breaks time
reversal invariance of a wave field. Nevertheless a high quality
WPC-retrofocusing of nonlinear acoustic beams takes place even in conditions of
strong phase distortions introduced by inhomogeneous medium. This phenomenon is
explained by the phase locking effect in the cascade harmonic generation in
nondispersive media [2]. Compensation of phase distortions by WPC is
demonstrated for second harmonic imaging using nonlinear conjugate beam [2] and
for WPC of selected harmonics of nonlinear incident beam as well [3]. [1]. A.P.
Brysev, L.M. Krutyansky, V.L. Preobrazhensky, Phys.- Usp., 41 (1998) [2]. Yu.
Pyl.nov, P. Pernod, V. Preobrazhensky, Appl. Phys. Letts., 78 553 (2001) [3].
L. Krutyansky, P. Pernod, A. Brysev, F.V. Bunkin, V. Preobrazhensky, IEEE UFFC,
April (2002)
Section
: 10