Characterization of periodic cavitation in optical tweezers

Microscopic vapor explosions or cavitation bubbles can be generated repeatedly in optical tweezers with a microparticle that partially absorbs at the trapping laser wavelength. In this work we measure the size distribution and the production rate of cavitation bubbles for microparticles with a diameter of 3 μm using high-speed video recording and a fast photodiode. We find that there is a lower bound for the maximum bubble radius R(max)∼2  μm which can be explained in terms of the microparticle size. More than 94% of the measured R(max) are in the range between 2 and 6 μm, while the same percentage of the measured individual frequencies f(i) or production rates are between 10 and 200 Hz. The photodiode signal yields an upper bound for the lifetime of the bubbles, which is at most twice the value predicted by the Rayleigh equation. We also report empirical relations between R(max), f(i), and the bubble lifetimes.