Heating of the phantom of a biological tissue by a phase conjugate ultrasonic beam

The local heating of an absorbing medium by an ultrasonic beam with a conjugate wave front has been experimentally demonstrated. Plastisol, which is a polymeric material close in acoustic properties to biological tissue, is used as the medium. An ultrasonic heating of $7.2\,^\circ$C has been obtained in a time of about $100$ s when the sample equipped with a thermocouple is placed between a focused piezoelectric transducer emitting a “probe wave” with a frequency of $5.0$ MHz and a system that reverses the ultrasonic wave front with amplification. The characteristic features of heating by ultrasonic beams with the conjugate front, as well as the prospects of applications of this effect in medicine and other fields, have been discussed.