Mutual coupling and synchronization of optically coupled quantum-dot micropillar lasers at ultra-low light levels

Sören Kreinberg,Kathy Lüdge,Christian Schneider,Ido Kanter,Xavier Porte,Benjamin Lingnau,Stephan Reitzenstein,Sven Höfling,David Schicke

doi:10.1038/s41467-019-09559-2

Abstract

Synchronization of coupled oscillators at the transition between classical physics and quantum physics has become an emerging research topic at the crossroads of nonlinear dynamics and nanophotonics. We study this unexplored field by using quantum dot microlasers as optical oscillators. Operating in the regime of cavity quantum electrodynamics (cQED) with an intracavity photon number on the order of 10 and output powers in the 100 nW range, these devices have high β-factors associated with enhanced spontaneous emission noise. We identify synchronization of mutually coupled microlasers via frequency locking associated with a sub-gigahertz locking range. A theoretical analysis of the coupling behavior reveals striking differences from optical synchronization in the classical domain with negligible spontaneous emission noise. Beyond that, additional self-feedback leads to zero-lag synchronization of coupled microlasers at ultra-low light levels. Our work has high potential to pave the way for future experiments in the quantum regime of synchronization.

Highlights

Synchronization of coupled oscillators at the transition between classical physics and quantum physics has become an emerging research topic at the crossroads of nonlinear dynamics and nanophotonics
The quantum dot (QD) microlasers, which we used for coupling experiments as sketched in Fig. 1, were realized by means of molecular beam epitaxy of planar microcavity structures and subsequent nanoprocessing of electrically driven micropillar cavities as we detail in Supplementary Note 1
Time delay (t2′–t1′) / ns Synchronization of coupled systems is at the heart of nonlinear dynamics and can lead to a plethora of dynamical patterns ranging from leader-laggard behavior to zero-lag synchronization

Summary

Introduction

Synchronization of coupled oscillators at the transition between classical physics and quantum physics has become an emerging research topic at the crossroads of nonlinear dynamics and nanophotonics. Situated at the crossroads between nonlinear dynamics, nanophotonics and quantum optics, cavity-enhanced microlasers are interesting devices to drive research on synchronized oscillators toward the quantum regime. They offer a rich spectrum of exciting physics with potential applications as coherent light sources in system-on-chip quantum technologies[27]. We apply bimodal semiconductor quantum dot (QD) micropillar lasers driven with intracavity photon numbers on the order of ten to study mutual coupling at ultralow light levels This detailed investigation on the dynamics of coupled micro- or nanolasers is of interdisciplinary and immediate importance for scientists working on the dynamics of nonlinear oscillators and for those interested in microscopic or nanophotonic lasers. Accurate numerical modeling supports our findings and allows us to reveal the underlying timeresolved character of the synchronized dynamics

Methods

Results

Conclusion