Characterization of periodic cavitation in an optical tweezer

Microscopic vapor explosions or cavitation bubbles can be generated periodically in an optical tweezer with a microparticle that partially absorbs at the trapping laser wavelength. In this work we correlate the size of the cavitation bubbles with the cycle frequency for microparticles with a diameter of 3 $mu$m. We use high speed video recording to measure the maximum bubble sizes and a fast photodiode to collect the trapping laser light scattered by both the particle and the transient bubble. We find an inverse relation between maximum bubble size and cycle frequency, consistent with a longer displacement of the microbead induced by larger bubbles and hence a longer time back to the waist. More than $94 %$ of the measured maximum bubble radiuses are in the range between 2 and 6 $mu$m, while the same percentage of the measured frequencies are between 10 and 200 Hz. The width of the scattered light signal for both particle and bubble during cavitation is proportional to the predicted lifetime for a spherical bubble. In this way we also show that it is possible to get good estimates of the bubble sizes and the cycle frequencies using a high speed photodiode.