Single-mode emission by phase-delayed coupling between nano-lasers

TL;DR

This paper demonstrates that phase-delayed coupling between nanolasers can achieve stable single-mode emission, improving brightness and coherence, with potential applications in photonic communication and lidar systems.

Contribution

It introduces a simple, robust method using phase-delayed coupling to enable stable single-mode operation in nanolaser arrays, surpassing previous complex architectures.

Findings

Phase delay separates mode thresholds near the PT symmetric exceptional point.

Stable single-mode lasing achieved in nanolaser dimers and arrays.

Enhanced power and lowered thresholds in large nanolaser arrays.

Abstract

Near-field coupling between nanolasers enables collective high-power lasing but leads to complex spectral reshaping and multimode operation, limiting the emission brightness, spatial coherence and temporal stability. Many lasing architectures have been proposed to circumvent this limitation, based on symmetries, topology, or interference. We show that a much simpler and robust method exploiting phase-delayed coupling, where light exchanged by the lasers carries a phase, can enable stable single-mode operation. Phase-delayed coupling changes the modal amplification: for pump powers close to the anyonic parity-time (PT) symmetric exceptional point, a high phase delay completely separates the mode thresholds, leading to single mode operation. This is shown by stability analysis with nonlinear coupled mode theory and stochastic differential equations for two coupled nanolasers and confirmed by realistic semi-analytical treatment of a dimer of lasing nanospheres. Finally, we extend the mode control to large arrays of nanolasers, featuring lowered thresholds and higher power. Our work promises a novel solution to engineer bright and stable single-mode lasing from nanolaser arrays with important applications in photonic chips for communication and lidars.