Spatio-Temporal and Spectral Transformation of Femtosecond Pulsed Beams with Phase Dislocation Propagating Under Conditions of Self-action in Transparent Solid-State Dielectrics

Self-action of a femtosecond optical vortex in fused silica at a wavelength of 1900 nm is analyzed by means of numerical simulations. The formation of a multi-focus ring structure is demonstrated. We show that self-focusing in a ring of relatively large radius occurs without plasma generation. The frequency spectrum of the pulse is broadening mainly into the Stokes band.