Unified model for breathing solitons in fibre lasers: Mechanisms across below- and above-threshold regimes

TL;DR

This paper presents a unified model that explains the mechanisms behind breathing solitons in fibre lasers across below- and above-threshold regimes, combining experimental validation and theoretical insights.

Contribution

The authors develop a comprehensive model incorporating spatial and temporal gain dynamics to distinguish the origins of different breathing soliton regimes in fibre lasers.

Findings

Below-threshold breathers result from Q-switching and soliton shaping.

Above-threshold breathers are dominated by Kerr nonlinearity and dispersion.

Experimental results validate the model's predictions.

Abstract

The emergence of breathing solitons in mode-locked lasers presents a fundamental challenge for the theoretical modelling of mode locking, with the mechanisms underlying below- and above-threshold breathing solitons, and the origins of their distinct nonlinear dynamics, remaining poorly understood. Here, we develop a model that incorporates both spatial and temporal gain dynamics, enabling us to elucidate the origins of these two classes of pulsating states. We show that below-threshold breathing solitons arise from the interplay between Q-switching and soliton shaping, whereas Kerr nonlinearity and dispersion dominate the formation of above-threshold breathers. The model further captures the markedly different dynamical properties of these regimes. Experimental observations corroborate the simulations, validating the predictive power of the framework. Beyond providing a refined theoretical basis for ultrafast laser design, this work advances the broader understanding of non-equilibrium dynamics in mode-locked lasers and offers new perspectives on breathing soliton phenomena across diverse physical systems.