Acoustic phase conjugation by nonlinear piezoelectricity. I. Principle andbasic experiments

The principle and the basic experimental results of the acoustic phase conj ugation by nonlinear piezoelectricity are described. Acoustic phase conjuga te waves at frequency omega are generated as a result of the interaction be tween incident acoustic waves at w and pump electric fields at 2 omega. An original explanation based on the modulation of sound velocity by the elect ric field together with the concept of time grating is given. Coupling equa tions for the PZT ceramics as a nonlinear material are derived. Experimenta l results of the sound velocity modulation and the phase conjugate generati on in nonlinear piezoelectric PZT ceramics are shown. Amplitude reflectivit y of the phase conjugation was 23% for the acoustic incidence at 10 MHz. (C ) 1999 Acoustical Society of America. [S0001-4966(99)02709-5].