Stability control of single bubble sonoluminescence light

Abstract

A micron-sized water bubble can be held fixed in a glass flask using an ultrasonic pressure field, and can be made to emit picosecond pulses of light that contains all colors. This phenomenon is called single bubble sonoluminescence (SBSL). The late Prof. Julian Schwinger had put forth a possible cause for SBSL, and postulated that the SBSL light consisted of photons that are emitted in pairs. Prior to testing for Schwinger's idea of photon pairs, we conducted experiments to measure the intensity fluctuations in SBSL using single-photon counting. By controlling the relative phase between the drive and feedback signals, through a PC computer, a light-emitting water bubble in an acoustically resonant flask could be maintained, while the fluctuations in the single-photon counts were limited to the square root of the number of detected photons. We demonstrate the possibility of maintaining a long-term stabilized sonoluminescence bubble, while simultaneously keeping the bubble light intensity at the level of single-photon sensitivity. Our results explicitly show that sonoluminescence light can be stabilized for experimental investigations that test for possible photon pairs from SBSL.