Dynamics of an acoustically trapped sphere in beating sound waves

A focused acoustic standing wave creates a Hookean potential well for small sphere and can levitate it stably against gravity. Exposing the trapped to second transverse traveling sound imposes an additional acoustical force that drives away from its mechanical equilibrium. The driving is shaped by interference between trapping driving. If, furthermore, detuned wave, oscillates at difference frequency. Far behaving like textbook driven harmonic oscillator, however, wave-driven oscillator instead exhibits remarkably rich variety of dynamical behaviors arising spatial dependence force. These include oscillations both harmonics subharmonics frequency, period-doubling routes chaos Fibonacci cascades. This model system therefore illustrates opportunities dynamic manipulation based on spectral control field, rather than control.