Study of intense femtosecond radiation scattering under optical breakdown of water

Abstract: The scattering of radiation in the zone of laser breakdown initiated in distilled water under the influence of a sequence of intense femtosecond pulses (Ti:Al₂O₃ laser, wavelength 800 nm, repetition rate 1 kHz) was studied. The pulse energy varied from 1 μJ to 1 mJ, while the process of bubble formation (liquid cavitation mode) was maintained throughout the specified range. Each pulse presented a train with the period of ~10 ns and, in addition to the main pulse (∼150 fs), contained several pre-pulses and post-pulses with a contrast of ∼70. The dependence of the shape and size of the breakdown zone at different levels of energy exposure were studied. The spectra of the scattered radiation and the dependence of its intensity on the laser energy were obtained for both the main pulse and the accompanying ones. The peculiarities of radiation energy dissipation in water at ultra-high laser radiation intensities and the contribution of the accompanying pulses to this process were analyzed.

Keywords: femtosecond laser radiation, laser-stimulated processes in liquids