Channels of Filaments of Axially Asymmetric Optical Vortices at a Wavelength of 1800 nm in a LiF Crystal

The formation of a set of filaments and plasma channels in a femtosecond optical vortex has been studied experimentally and numerically. A longitudinal distribution of color center tracks with a length of 1 cm written in a LiF crystal by an axially asymmetric beam in the single-pulse regime has been detected experimentally for the first time. It has been shown that, at a sufficient excess of the peak power over the critical value, two hot points on the annular profile of vortex beam separated by the phase dislocation region form sequences of color center tracks; each sequence in the cross section of the beam is localized near the initial hot point. Secondary filaments and the corresponding tracks appear with an increase in the pulse energy. The parameters of femtosecond filaments in LiF have been numerically estimated.