Soliton-pair dynamical transition in mode-locked lasers

TL;DR

This study demonstrates control over two-soliton waveforms in mode-locked lasers by tuning pump current, inducing a transition from loosely bound to tightly bound soliton pairs, with insights from experiments, simulations, and theory.

Contribution

It introduces a method to manipulate soliton interactions in fiber lasers via pump current, revealing a dynamical transition driven by noise-mediated forces.

Findings

Two-orders-of-magnitude reduction in soliton separation achieved.

Dynamical transition between phase-incoherent and phase-locked pairs demonstrated.

Pulse separation governed by dispersive-wave pedestal shape.

Abstract

Multi-soliton mode-locked laser waveforms are much sought as a complex light source for research and applications, but are difficult to manipulate effectively because of the elaborate and diverse interactions present. Here we present an experimental, numerical, and theoretical study of the interaction and control of the internal dynamics of a two-soliton waveform in a mode-locked fiber laser. Using the pumping current as a control agent, we demonstrate experimentally a two-orders-of-magnitude reduction in the separation of a bound soliton pair, inducing a dynamical transition between a loosely bound, phase-incoherent pair, and a tightly bound phase-locked pair. We show on the basis of a Haus-model numerical simulation of the recently-proposed noise-mediated interaction theory, that the pulse separation and dynamical transition are governed by the shape of the dispersive-wave pedestals. We explain the dynamical transition by showing analytically, within a simplified theory, that the noise-mediated interaction becomes purely attractive when the pedestals energy drops below a threshold. This work demonstrates the ability to control the waveform through the interaction forces, without external intervention in the light propagation in the laser.