Abstract

On the Physical Interest of Some Numerical Methods for Wave Phase Conjugation in Active Media

A.Merlen (Laboratoire de Mecanique de Lille (LML-URA CNRS 1441), Villeneuve d'Ascq, 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); P.Pernod (Institut d'Electronique et de Micro-electronique du Nord (IEMN-DOAE-UMR CNRS 8520), Ecole Centrale de Lille, Villeneuve d'Acsq, France)

e-mail: alain.merlen@univ-lille1.fr

Parametric wave phase conjugation (WPC) in an active medium is of fundamental interest for many applications in ultrasonics [1]. Magneto-acoustic WPC provides not only the time reversal of the incident waves but also a giant amplification in supercritical mode. There is no exact analytical solution to the general problem of nonstationary and nonlinear parametric WPC. Recently a new numerical approach has been tested successfully for the simulation of nonstationary linear pumping [2]. The extension of this method to a nonlinear pumping is presented in this paper for the 1D configuration. The simulations provide the spatial distribution of the normal stress and temporal form of the conjugate wave for two nonlinear mechanisms of feedback of the elastic waves on the pumping source (pumping depletion and phase mechanisms). Effect of each process on the output power limitation of the phase conjgator is clarified, and the pumping depletion mechanism is found to be closer to experimental situation. Numerical solutions for extension to the multidimensional problem will be discussed. [1] A. Brysev, L. Krytyansky, P. Pernod, V. Preobrazhensky, Appl. Phys. Letters, 76 (21), (2000) [2] S. Ben-Khelil, A. Merlen , V.L.Preobrazhensky, P. Pernod, JASA, 109 (1) (2001)

Section : 10