Optical pattern formation in self-focusing and self-defocusing diffractively thick media

TL;DR

This paper explores how cold atomic clouds exhibit optical pattern formation influenced by self-focusing or self-defocusing nonlinearities, emphasizing the importance of a diffractively thick medium model for accurate description.

Contribution

It provides a comparative analysis of pattern formation in self-focusing versus self-defocusing regimes in cold atomic clouds, highlighting the role of diffractively thick media.

Findings

Pattern formation depends on the sign of light detuning.

Diffractively thick medium description is essential for accurate modeling.

Spontaneous symmetry breaking leads to transverse spatial patterns.

Abstract

Cold atomic clouds constitute highly resonant nonlinear optical media, whose refractive index can be easily tuned via the light frequency. When subjected to a retro-reflected laser beam and under appropriate conditions, the cloud undergoes spontaneous symmetry breaking and spatial patterns develop in the transverse cross-section of the beam. We investigate the impact of the sign of the light detuning from the atomic resonance on these patterns, thus directly comparing pattern formation for self-focusing and self-defocusing nonlinearities. Our observations emphasize the need for a ''diffractively thick'' medium description of the light-cloud interaction, where diffraction and nonlinear propagation inside the sample are taken into account.