High-pressure nano-seismology: Use of micro-ring resonators for characterizing acoustic emissions

Microring resonator (MRR) ultrasound detectors provide orders of magnitude greater sensitivity and frequency range (to < 10 Pa, from DC to 100 s of MHz) than previously achieved in recording acoustic emissions from materials at high pressures. We characterize acoustic emissions from crystal-structural phase transitions in Si to pressures of 50 GPa, well beyond the brittle-ductile transition at room temperature, and find that the number of events increases nearly tenfold for each decade reduction in the duration of recorded events. The shortest-duration events arrive in clusters, suggestive of a self-propagating, transformation-catalyzed process.