Model description of intense ultra-short laser pulse filamentation: multiple foci and diffraction rays

Abstract

We present a new outlook on the problem of ultra- short laser pulse self-focusing and filamentation when prop- agating in air. Two previously known qualitative physical models of optical pulse filamentation scenario, the dynamic multiple focusing, and the wave-guiding models, are con- sidered and partially revisited. In terms of the averaged (ef- fective) laser beam radius, the filament is treated as a net product of layer-by-layer (in time) self-focusing of sepa- rate temporal pulse slices. By means of the developed time- averaged diffraction ray tracking technique, the crucial role of the diffraction effects in the formation of a light filament and next following a low-divergent light channel near the beam axis is revealed.