Breather molecular complexes in a passively mode-locked fibre laser

TL;DR

This paper reports the experimental observation of complex breather molecules in a passively mode-locked fibre laser, revealing long-range interactions, diverse molecular formations, and dynamic behaviors of breathing solitons.

Contribution

It presents the first observation of multi-breather complexes and their interactions in a fibre laser, expanding understanding of breather dynamics beyond diatomic molecules.

Findings

Observation of multi-breather molecules and complexes

Inter-molecular separation exceeds stationary soliton distances

Detection of breather collisions and annihilation phenomena

Abstract

Breathing solitons are nonlinear waves in which the energy concentrates in a localized and oscillatory fashion. Similarly to stationary solitons, breathers in dissipative systems can form stable bound states displaying molecule-like dynamics, which are frequently called breather molecules. So far, the experimental observation of optical breather molecules and the real-time detection of their dynamics have been limited to diatomic molecules, that is, bound states of only two breathers. In this work, we report on the observation of different types of breather complexes in a mode-locked fibre laser: multi-breather molecules, and molecular complexes originating from the binding of two breather-pair molecules or a breather pair molecule and a single breather. The inter-molecular temporal separation of the molecular complexes attains several hundreds of picoseconds, which is more than an order of magnitude larger than that of their stationary soliton counterparts and is a signature of long-range interactions. Numerical simulations of the laser model support our experimental findings. Moreover, non-equilibrium dynamics of breathing solitons are also observed, including breather collisions and annihilation. Our work opens the possibility of studying the dynamics of many-body systems in which breathers are the elementary constituents.