High-Resolution Simulation of Externally Injected Lasers Revealing a Large Regime of Noise-Induced Chaos

Sean P O’Duill,Liam P Barry

doi:10.3390/photonics9020083

Abstract

We present comprehensive numerically simulated scans of the spectral evolution of the output from a single-mode semiconductor laser diode undergoing external light injection. The spectral scans are helpful to understand the different regimes of operation as well as the system evolution between each state: i.e., locked state, four-wave mixing, pulsations, chaos. We find that, when under strong injection, when the injected power equals about half of the laser power, two distinct regions of chaotic behaviour are observed. One of the chaotic regions arises due to the usual period-doubling route to chaos; the other chaotic region is a blurring of what would be higher-order period pulsations whose periodicity is broken by spontaneous emission and the laser spectrum is chaotic. Eliminating spontaneous emission in our simulations confirms the latter chaotic region becomes a region with higher-order pulsations.

Highlights

To the best of our knowledge, we find a chaotic regime solely created from noise-induced chaos, when spontaneous emission (SE) is removed from the simulation that the region is entirely comprised of high-order pulsations of periodicity
Through numerical solutions, the spectral evolution of an externally injected laser system and the role that SE plays in washing out higher-order pulsation regimes in the dynamics of externally injected lasers
We identify an operating regime comprised entirely of noise-induced chaos destroying higher-order pulsations, especially under strong injection powers

Summary

Introduction

External laser injection-locking is a curious field of study due to the range of dynamical states that are produced: laser synchronisation; chaos; four-wave mixing (FWM); selfpulsation and associated period-doubling routes to chaos [1,2,3,4,5,6,7,8,9,10]. Previous studies attributed SE to be the cause of an observed absence of a period-doubling route to chaos [14]; a more formal analysis [15] examined the behaviour of noise-induced chaos when the external-injected laser system was in a delicate high order pulsation state and that study found that SE could induce chaotic behaviour.

Materials and Methods

High-Resolution Spectral Scans Due to External-Injection

Influence of Spontaneous Emission

Findings

Conclusions