WAVE PHASE-CONJUGATION OF ULTRASONIC BEAMS

The current state of the acoustic wave phase conjugation (WPC) problem is reviewed. The generation of phase conjugate ultrasonic waves is di scussed with emphasis on the parametric method using electromagnetic p umping in solids. The giant-amplification supercritical parametric WPC mode is considered in detail. Ultrasonic WPC with a gain in excess of 80 dB is demonstrated for a soft magnetic ceramics based amplifier. T he high quality of supercritical parametric WPC is confirmed by acoust ooptical visualization. Acoustic WPC effects, such as anomalous sound reflection at the WPC mirror and the self-focusing and self-targeting of phase conjugate beams incident on a scatterer in a liquid, are show n. Recent experimental results demonstrating WPC's potential for appli cations are presented.