Phase change-driven photoacoustic oscillations induced by periodic irradiation

The photo-acoustic effect is a well-documented phenomenon in which the periodic irradiation of an absorbing media produces an acoustic wave, modulated by thermal expansion. However, little is known about the effect imparted by phase change on this mode of energy conversion, nor has it been considered as a potential method of power production. Herein, we report high-amplitude photo-acoustic oscillations, of up to 145 dB, induced upon irradiation of a water film on the wall of an acoustic loop resonator. While the driving power is quite low (∼4 W), the photo-acoustic oscillations are shown to be significantly amplified by the introduction of phase change in the acoustic cycle. A reduced-order model is formulated and is able to recover key characteristics of the acoustic oscillations, in reasonable agreement with experimental results, and confirms the underlying mechanism of pressure modulation by the phase change. The results presented here can potentially pave the way to improved, solar-driven acoustic energy conversion devices.