Nonlinear piezoelectric oscillators coupled through a complex acoustic cavity, synchronization and stimulated emission

Richard Weaver, Department of Physics, University of Illinois at Urbana-Champaign

We report theory, measurements and numerical simulations on nonlinear piezoelectric ultrasonic devices with stable limit cycles coupled to reverberant elastic bodies. The devices are shown to exhibit behavior familiar from the theory of coupled auto-oscillators, they adjust their frequencies to the spectrum of the body, they can be entrained by an applied field, and they can synchronize to each other. Special attention is paid to the phase of entrainment. It is found that, depending on details, the phase is such that the oscillator is in a state of stimulated emission: the incident field amplifies the ultrasonic power emitted by the oscillator. These behaviors are essential to eventual design of an ultrasonic system that would consist of a number of such devices all synchronized to their mutual field, a system that would be an analog to a laser. A prototype uaser is constructed.