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Abstract |
Low Frequency Emission by Nonlinear
Interaction of Phase Conjugate Ultrasound Waves
Y.Pyl'nov (Moscow Institute of
Radioengineering, Electronics and Automation, Moscow, Russia, and Institut
d'Electronique et de Microelectronique du Nord (IEMN-DOAE-UMR CNRS 8520), Ecole
Centrale de Lille, Villeneuve d'Ascq, France); 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)
e-mail:
pylnov@yandex.ru
Low
frequency emission (LFE) by means of parametric interaction of ultrasound beams
is of interest for various applications in nonlinear acoustic imaging,
elastography, vibro-acoustics etc. Interaction of waves can be distorted
dramatically by phase aberrations when propagation medium is essentially
inhomogeneous. The way to compensate phase distortions is to use the phenomenon
of wave phase conjugation of acoustic beams of intensity high enough for
manifestation of nonlinear effects. In the present paper, low combination
frequency emission by means of nonlinear interaction of phase conjugate
ultrasound beams is studied experimentally and theoretically. Phase conjugation
effect is used for automatic overlap of interacting focused beams of
frequencies 10MHz and 11MHz. Interaction of beams propagating in a homogeneous
liquid and beams scattered by an object immersed in a liquid are considered.
While variation of the object position for resonance interaction of
co-directional waves does not affect on phase of the emitted wave of low
frequency (difference frequency 1 MHz), the anomalous phase shift proportional
to the sum of frequencies (21 MHz) is obtained for non-resonance interaction of
contra-propagating waves. Application of anomalous phase shift for "supper
resolution" in object positioning by means of nonlinear low frequency
emission is discussed.
Section
: 10