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2015: “Fingerprints” of the IR laser superfilament in water on microseconds

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Physicists from Lomonosov Moscow State University studied the dynamics of multiple cavitation bubbles excited by a fs laser superfilament and developed a new approach for their control by laser pulse energy and external focusing.

For the first time an innovative method of controlling the dynamics of cavitation bubbles excited by the distributed laser-plasma source (filament) was demonstrated. Tight focusing and peak power much above the critical power of self-focusing make possible to achieve high intensities (~1014W/cm2) on the filament axis at distances several times greater than the length of the laser beam waist. This creates conditions for an efficient energy delivery to the medium and makes possible a precise "shock" impact on the environment. The energy and the size of the cavitation bubble depend on the electron density along the filament axis. Therefore, the control of the laser pulse energy, focusing parameters and aberrations added to the optical system allow us to create the specified pressure profiles, as well as the refractive index within the medium, that can be used in the femtotechnology .

The article also shows, how the aberrations (result of the laser radiation tight focusing in the volume of condensed matter) can not only play a negative role (reducing spatial resolution, creating additional aberration maxima, etc.), but also a positive role. Aberrations create the complex pattern of cavitation bubbles, which leads to an efficient energy exchange between them and guided jets, emitted in the final stages of the cavitation bubbles evolution.

This work was supported by the Development Program of Lomonosov Moscow State University. The results were published in the paper: F.V. Potemkin and E.I. Mareev, Dynamics of multiple bubbles, excited by a femtosecond filament in water, Laser Phys. Lett. 12, 015405 (2015).