Self-focusing of high-intensity beams with grid structures

TL;DR

This paper introduces a grid beam structure that suppresses self-focusing in high-power laser beams, potentially preventing damage in optical systems by redistributing optical power.

Contribution

It proposes a novel transverse grid beam design that mitigates self-focusing through nonlinear inter-beamlet interactions and identifies optimal grid configurations.

Findings

A $N imes N$ grid beam undergoes multi-stage self-focusing depending on lattice spacing.

Certain grid layouts can transmit more power than the critical self-focusing limit.

Derived a numerical relation between grid spacing and beamlet size.

Abstract

Laser beams with high optical power propagating in a Kerr medium can undergo self-focusing when their power exceeds a critical power determined by the optical properties of the medium. The highly concentrated energy close to the in the region of the self-focus can lead to other nonlinear phenomena and cause significant irreversible damage to the material. We propose a transverse grid beam structure that effectively suppresses self-focusing even in the absence of other competing effects through the redistribution of optical power by inter-beamlet nonlinear interaction. We find that a beam with a $N \times N$ grid structure with optimized lattice spacing undergoes a dimension-dependent multi-stage self-focusing. We also identify specific grid layouts that can increase the total transmitted power beyond that permitted by the critical level of self-focusing for each beamlet. Lastly, we derive a general numerical relation between the optimal grid lattice spacing and the size of beamlets. Our results could potentially inform the use of beam shaping to prevent damage to optical components in high-powered and directed-energy applications.