Coherent pulse interactions in mode-locked semiconductor lasers

TL;DR

This paper investigates the complex interactions of multiple pulses in mode-locked semiconductor lasers with delayed feedback, revealing diverse dynamical regimes and stability phenomena through reduced effective equations.

Contribution

It introduces a novel reduced model capturing pulse interactions and dynamics in mode-locked lasers with feedback, highlighting complex behaviors and bifurcations.

Findings

Pulses exhibit complex interactions including coherent and incoherent regimes.

Multiple stable regimes and bifurcations are identified.

Pulse arrangements can be equidistant or non-equidistant with different phase relations.

Abstract

We study the dynamics of multipulse solutions in mode-locked lasers in presence of time-delayed feedback stemming, e.g., from reflections upon optical elements, and carrier dynamics. We demonstrate that the dynamics of such a high dimensional problem can be successfully described by some effective equations of motion for the pulses' phases and positions. Analyzing the reduced vector field permits disclosing a highly complex dynamics where coherent and incoherent interactions compete. The latter lead to regimes in which pulses can be equidistant or non-equidistant and also have different phase relations. Multi-stability between regimes is also observed as well as emerging limit cycles and global heteroclinic bifurcations in phase space.