The work presents the results on the influence of the temperature of a turbulent layer on the transverse energy structure of femtosecond (multi-ring and Gaussian) laser beams. Gaussian and multi-ring beam profiles exhibit a monotonous growth in the number of intense light maxima with increasing the strength turbulence of air jet and increasing laser pulse energy. The formed intense light channels (~ 1011 W/cm2) make it possible to excite two-photon fluorescence of dyes with a signal level that makes it possible to take at a distance of 100 m.
The measurements of the angular distribution of two-photon-excited fluorescence of a dye solution in an aqueous aerosol are reported. It is shown that the fluorescence of an aerosol with a dye is one and a half to two times greater in the backward direction than in the forward direction.
We present the results of the turbulent layer influence on the characteristics of the filamentation domain at the path beginning for the beams with a diameter of 2.5 and 5 cm. Addition of turbulence results in the fact that the beginning of the multiple filamentation domain (MFD) to the source coming closer. Decreasing of the distance to the beginning and end of the MFR in the presence of turbulence is inappreciable (<10%). The turbulent layer formed at the beginning of the path leads to a multiple increase in the number of the intense channels (~ 1011-1012 W/cm2) with a length >100 m.
The results of the experiments on the excitation and detection of two-photon fluorescence of the dyes by the intense light channels generated by controlling the wavefront of the femtosecond laser pulses are presented. Emission of the dyes and the detection of the backward signal were carried out according to the lidar scheme at a distance of 100 m from the source.
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