Deterministic polarization chaos from a laser diode

TL;DR

This paper demonstrates for the first time that a free-running laser diode can generate deterministic polarization chaos due to nonlinear mode coupling, challenging previous assumptions about laser chaos generation.

Contribution

It provides the first experimental and theoretical evidence of chaos in a free-running laser diode caused by nonlinear polarization mode coupling, without external forcing.

Findings

Identified chaos in experimental time-series.

Theoretically modeled bifurcations leading to chaos.

Polarization chaos differs from noise-driven mode hopping.

Abstract

Fifty years after the invention of the laser diode and fourty years after the report of the butterfly effect - i.e. the unpredictability of deterministic chaos, it is said that a laser diode behaves like a damped nonlinear oscillator. Hence no chaos can be generated unless with additional forcing or parameter modulation. Here we report the first counter-example of a free-running laser diode generating chaos. The underlying physics is a nonlinear coupling between two elliptically polarized modes in a vertical-cavity surface-emitting laser. We identify chaos in experimental time-series and show theoretically the bifurcations leading to single- and double-scroll attractors with characteristics similar to Lorenz chaos. The reported polarization chaos resembles at first sight a noise-driven mode hopping but shows opposite statistical properties. Our findings open up new research areas that combine the high speed performances of microcavity lasers with controllable and integrated sources of optical chaos.