Spectral Broadening of Femtosecond Optical Vortices at Filamentation in Fused Silica under the Conditions of the Anomalous Group Velocity Dispersion.

Features of the spectral broadening of femtosecond optical vortices at self-action in a medium with the anomalous group velocity dispersion have been studied experimentally and numerically. It has been found that the broadening of the frequency–angular spectrum is accompanied by the appearance of localized maxima in the Stokes and anti-Stokes regions, which have a strip structure, near the nonlinear focus. It has been shown that in the medium with the anomalous group velocity dispersion the broadening of the spectrum in an optical vortex is smaller than that in a Gaussian beam at the same excess of the power above the critical value. [ABSTRACT FROM AUTHOR]