Phase incoherent photonic molecules in V-shaped mode-locked VECSELs

TL;DR

This paper investigates the emergence of incoherent, non-locally bound pulse molecules in V-shaped mode-locked VECSELs, revealing their bistability, addressability, and the influence of cavity geometry through a delay differential equation model.

Contribution

It introduces a model explaining how cavity geometry and non-local coupling produce incoherent photonic molecules in VECSELs, with analytical predictions of cluster spacing.

Findings

Pulse clusters are bistable with the off state.

Clusters are individually addressable.

Analytical prediction of cluster spacing.

Abstract

Passively mode-locked vertical external-cavity surface-emitting semiconductor lasers (VECSELs) composed of a gain chip and a semiconductor saturable absorber have been drawing much attention due to their excellent performance figures. In this work we investigate how localized structures and incoherent, non-locally bound, pulse molecules emerge in a long cavity VECSELs using a V-shaped cavity geometry. We show that these states are bistable with the laser off state and that they are individually addressable. Using a model based upon delay differential equations, we demonstrate that pulse clusters result from the cavity geometry and from the non-local coupling with the gain medium; this leads to locally independent, yet globally bound phase, incoherent photonic molecules. Using a multiple time-scale analysis, we derive an amplitude equation for the field that allows us to predict analytically the distance between the elements of a cluster.