Showing papers by "V.P. Kandidov published in 2004"
TL;DR: In this article, the authors observed a universal phenomenon of the competition among multiple filaments generated during the propagation of intense femtosecond laser pulses in air, and they showed that the fluorescence signal from the excitation of nitrogen molecules inside the plasma channel contains important information pertaining to the formation and interaction of multiple filament.
Abstract: We observed a universal phenomenon of the competition among multiple filaments generated during the propagation of intense femtosecond laser pulses in air. We show that the fluorescence signal from the excitation of nitrogen molecules inside the plasma channel contains important information pertaining to the formation and interaction of multiple filaments. The detected backscattered nitrogen fluorescence from inside the filaments yielded irregular changes from shot to shot which cannot be explained by fluctuation arising from the initial laser pulse itself. Numerical simulations reveal a complex dynamics of multiple filament propagation and interaction dynamics that depends strongly on the initial perturbations of the laser beam. The irregular changes of the fluorescence signal are attributed to the interference between adjacent hot spots that evolve into filaments which give rise to new hot spots (filaments) in between, and thus give the appearance of the fusion or branching of filaments.
128 citations
TL;DR: In this article, a large divergence of the beam pattern at the anti-Stokes side was experimentally observed, which contrasts the tiny spots at the Stokes side at long distances.
Abstract: We present here a recent experiment on long-distance free propagation of powerful ultrafast laser pulses. A large divergence of the beam pattern at the anti-Stokes side was experimentally observed, which contrasts the tiny spots at the Stokes side at long distances, while the pattern at the central laser wavelength was practically unchanged (self-guiding). White light laser self-interference patterns were also recorded and discussed.
57 citations
TL;DR: In this paper, a method for spatial regularisation of chaotically located filaments, which appear in a high-power femtosecond laser pulse, is proposed, numerically substantiated, and experimentally tested.
Abstract: A method for spatial regularisation of chaotically located filaments, which appear in a high-power femtosecond laser pulse, is proposed, numerically substantiated, and experimentally tested. This method is based on the introduction of regular light-field perturbations into the femtosecond-pulse cross section.
23 citations
TL;DR: In this article, the authors studied the self-focusing power of collimated elliptic Gaussian beams and showed that the critical self-focus power increases with increasing the axial ratio of the initial elliptic cross section.
Abstract: Stationary self-focusing of collimated elliptic Gaussian beams is studied numerically. It is shown that the critical self-focusing power increases with increasing the axial ratio of the initial elliptic cross section. Self-focusing is accompanied by oscillations of the beam transverse size caused by the competition between the diffraction-limited divergence and nonlinear compression. As the power of the beam with the axial ratio a/b{>=}3 increases, aberration self-focusing occurs, at which, after the formation and competition of several intensity maxima in the beam cross section, a global maximum appears at the beam centre, which forms a nonlinear focus. The approximation formula for the self-focusing distance is generalised to elliptic beams. (nonlinear optical phenomena)
20 citations