Experimental Proof of the Effect of Induced Optical Coalescence of Bubston Clusters at Water Breakdown Induced by Picosecond and Nanosecond Laser Pulses

The optical breakdown in water, caused by irradiation with nanosecond and picosecond laser pulses at a wavelength of 1064 nm, has been studied. It is proven experimentally that optical breakdown centers are both individual nanobubbles of dissolved gas and clusters formed by these nanobubbles. It is found that the first stage of optical breakdown on nanobubble clusters implies induced optical coalescence (collapse) of such a cluster and formation of a macroscopic vapor bubble. The obtained experimental results for nanosecond and picosecond pulses are in good agreement with the predictions of the previously developed theoretical model.