Spatiotemporal mode decomposition of ultrashort pulses propagating in graded-index multimode fibers

TL;DR

This paper introduces a spatiotemporal mode decomposition method to analyze ultrashort pulse propagation in graded-index multimode fibers, revealing that mode power distributions follow Bose-Einstein and Rayleigh-Jeans laws under different regimes.

Contribution

It presents a novel technique for decomposing mode power in ultrashort pulses and uncovers the statistical laws governing mode distribution in different propagation regimes.

Findings

Mode power distribution follows Bose-Einstein law in dispersive regime.

In soliton regime, distribution approaches Rayleigh-Jeans law.

Power diffusion results from linear and nonlinear mode coupling.

Abstract

We develop a spatiotemporal mode decomposition technique to study the mode power distribution of ultrashort pulses emerging from long spans of graded-index multimode fiber, for different input laser conditions. We find that beam mode power content in the dispersive pulse propagation regime can be described by the Bose-Einstein law, as a result of the process of power diffusion from linear and nonlinear mode coupling among nondegenerate mode groups. In the soliton regime, the output mode power distribution approaches the Rayleigh-Jeans law