Effect of Power Losses on Self-Focusing of High Intensity Laser Beam in Gases

TL;DR

This theoretical study investigates how power losses and plasma-induced defocusing affect self-focusing of high-intensity laser beams in gases, challenging existing concepts and proposing new criteria for filamentation.

Contribution

It introduces a new criterion for self-focusing considering spatial distribution and plasma effects, and proposes a hypothesis for multiple filamentation.

Findings

Power losses of 10%-80% occur at the beam periphery.

The traditional critical power concept for self-focusing is inconsistent with spatially distributed beams.

A new criterion for self-focusing and a filamentation hypothesis are proposed.

Abstract

A theoretical study of power loss from periphery of an ultrashort pulse laser beam and temporally resolved defocussing produced by laser induced plasma are performed using paraxial approximation. Our analysis incorporate consideration of spatial distribution of the laser beam irradiance and the results show that substantial power losses (10%-80%) occur from the beam periphery limiting length of a filament. It was also shown that generally accepted concept of self-focusing critical power is inconsistent with consideration of self-induced refraction of spatially distributed laser beam. A new criterion for self-focusing and hypothesis for multiple filamentation are proposed.