S. S. Golik

Kerr-driven nonlinear refractive index of air at 800 and 400 nm measured through femtosecond laser pulse filamentation

The filamentation dynamics of 15u2009GW femtosecond laser pulses at 800 and 400u2009nm wavelengths upon their tight focusing in air is studied experimentally. The spatial position and extent of plasma channel formed within the filamentation zone as a function of laser pulse power are investigated. The processing of the experimental data according to the Marburger formula by J. H. Marburger [Prog. Quantum. Electron. 4, 35 (1975)] and the dispersion relations for air cubic nonlinearity has allowed to estimate the effective value of the Kerr-driven air refractive index on 400u2009nm as 5.36u2009×u200910−19 cm2/W with a 5% error.

Filamentation of femtosecond Ti:Sapphire laser pulses at the first and second harmonics in liquid media

The experimental results on transformation of the spectral and spatial characteristics of femtosecond Ti:Sapphire-laser pulses with wavelengths of 800 and 400 nm during filamentation in liquid media are presented. It is shown that spectral broadening of a laser pulse at both harmonics at the expense of phase self-modulation in a medium with cubic nonlinearity depends on pulse power and beam diameter. Emission with a maximum at 464 nm is observed during filamentation of the pulses with a wavelength of 400 nm in distilled water, which corresponds to stimulated Raman scattering of the water. Fluorescence of dissolved organic matter is observed in sea water.

Filamentation length of high-power sharply focused femtosecond laser radiation in air. Effect of light beam size

The results of laboratory experiments on measurements of the length and position of the filamentation zone of femtosecond GW laser radiation at wavelengths of 800 and 400 nm propagating in air under conditions of sharp external focusing are presented. Dependencies of the length of the radiation filamentation zone on its initial radius and power are studied. Qualitatively new regularity is obtained, which consists in invariance of the observed length of the beam filamentation under variations in its diameter with the assumption of equality of the initial intensities. The feature is not typical for collimated radiation and is connected with the dominance of geometrical focusing over Kerr self-focusing of a beam during filament formation.

Interaction of GW laser pulses with liquid media. Part 2. Spectral and angular characteristics of scattering by millimeter water droplets

We present the results of experimental investigations of interaction between femtosecond laser pulses of gigawatt power and suspended distilled water droplets of millimeter size. The angular distribution of the spectral characteristics of water particle emission is investigated.

Multiple filamentation of collimated Ti:Sapphire laser beams in water

The results of experimental studies of femtosecond laser pulse filamentation in water are described. The dependencies of the number of filaments, spectrum width, distance of nonlinear focusing, and diameter of filamentation zone on the laser pulse power are measured. Existence of a segment on the scale of relative power is marked out, where the number of filaments increases dramatically.

Study of filamentation dynamics of ultrashort laser radiation in air: beam diameter effect

A single filamentation of femtosecond gigawatt laser radiation with a millimeter-size aperture upon collimated and sharply focused propagation in atmospheric air at 800 nm and 400 nm wavelengths is studied both theoretically and experimentally. The influence of beam initial radius on the parameters of the forming filament is analyzed. Three filament parameters, namely, start coordinate, filament length, and longitudinal continuity are considered. We report that unlike Marburgers formula the single filamentation onset reveals marked nonquadratic dependence on the laser beam radius providing the same initial pulse power. Additionally, for sharply focused radiation the minor dependence of the filament length on the laser beam diameter at the constant initial pulse intensity was experimentally revealed.

Microstructure of the multiple filamentation region of femtosecond laser radiation in a solid dielectric

Properties of multiple filamentation of gigawatt femtosecond laser pulses in optical glass are considered. The fine structure of the plasma region that is produced upon photoionization of quartz and accompanies light filaments are analyzed experimentally and in numerical simulation. The dependence of the number, position, and length of individual generations of plasma channels on the laser energy is studied for the first time. The role of pulse refocusing events in the plasma region formation is discussed.

Multiple filamentation of collimated beams Ti:Sapphire-laser in water

The results of experimental studies of filamentation of femtosecond laser pulses in water is presented. Measured the number of filaments, the spectral width of the laser radiation, nonlinear focusing distance, the diameter of the field of filamentation power laser pulses. Noted the existence of plot on the scale of the relative power in passing which the explosive growth in the number of filaments.