Optical beam propagation inside a graded-index fiber with saturable nonlinearity

TL;DR

This paper theoretically investigates the propagation of optical beams in graded-index fibers with saturable nonlinearity, revealing bistable solitons and their stability, and analyzing how saturation affects beam dynamics.

Contribution

It introduces a variational approach to identify bistable spatial solitons in saturable nonlinear fibers and analyzes their stability and oscillatory behavior.

Findings

Existence of bistable spatial solitons due to saturable nonlinearity

Stability of solitons linked to the saturating nature of the nonlinearity

Oscillating solutions with periods increasing with saturation level

Abstract

We study theoretically the spatial evolution of optical beams inside a graded-index fiber exhibiting saturable nonlinearity. Utilizing an approach based on the variational principle, we identify the existence of bistable spatial solitons inside such a nonlinear medium, whose stability, analyzed through a linear stability analysis, is due to the saturating nature of the nonlinearity. Spatial solitons adhere to a specific amplitude-width relationship. Any deviation from this relationship leads to oscillating-type solutions with a period that increases with saturation level of the nonlinearity. Theoretically calculated values of this period agree well with numerical findings.