# Synchronization of complex spatio-temporal dynamics with lasers

## TL;DR

This paper shows how lasers can synchronize complex patterns of light, which could help in secure communication technologies.

## Contribution

The study demonstrates synchronization of spatio-temporal dynamics in lasers for secure communication applications.

## Key findings

- Broad-area lasers exhibit chaos through nonlinear coupling of modes.
- Synchronization and anti-synchronization regimes are observed when coupling two lasers.
- Correlation coefficients between 0.2 and 0.9 are measured depending on dynamics and time scale.

## Abstract

Synchronization is the spontaneous alignment of the dynamics of weakly-coupled oscillators. In addition to temporal dynamics like periodic and chaotic oscillations, also the spatio-temporal dynamics of spatially-extended systems like wildlife populations can synchronize. We exploit here the intrinsic spatio-temporal complex dynamics of broad area lasers to demonstrate such synchronization at lab-scale. Broad-area vertical-cavity surface-emitting lasers (BA-VCSELs) exhibit chaos from the nonlinear coupling between laser modes with different spatial profiles and polarization. When coupling two BA-VCSELs, several synchronization and anti-synchronization regimes are observed, highlighting the complex interplay between oscillating modes with different frequencies and spatial patterns. The correlation coefficient varies between 0.2 and 0.9 depending on the dynamics and on the time scale under analysis. Besides its fundamental interest, our experiment with commercial devices marks the first step towards real-world spatial multiplexing in multiple user physical-layer secure communication based on chaos synchronization.