Synchronized-piezoelectric auto-oscillators, a classical analog laser

Abstract

We report the behavior of two ultrasonic transducers, each part of an auto-oscillating Wein bridge, in contact with a high-Q elastic body. In particular, we compare the behavior of the one- and two-transducer cases. Each transducer oscillates erratically, and at its own frequency, when isolated and not in contact with the elastic body. When placed in contact with an elastic body, each transducer then stabilizes at a frequency close to the range of the original erratic oscillation, where it excites a ‘‘mode’’ (not necessarily a normal mode of the body) of the system. When both are in contact with the elastic body, a new mode is excited, and both transducers oscillate at the same frequency. They are locked to themselves and to each other by virtue of their mutual access to the same acoustic system, and the power output of the pair is, presumably, approximately 4 times as great as that of either transducer by itself.