Rate equation analysis and non-Hermiticity in coupled semiconductor laser arrays

TL;DR

This paper analyzes coupled semiconductor laser arrays using rate equations, highlighting the role of nonlinearities and cavity detuning in mode control, and explores parity-time symmetry and exceptional points in the system.

Contribution

It introduces a comprehensive rate equation model that incorporates nonlinearities and cavity detuning, revealing new mechanisms for mode control and symmetry properties in laser arrays.

Findings

Carrier-induced nonlinearities are critical for mode control.

Gain contrast from cavity detuning enables mode selection.

Unbroken parity-time symmetry and exceptional points are identified.

Abstract

Optically-coupled semiconductor laser arrays are described by coupled rate equations. The coupled mode equations and carrier densities are included in the analysis, which inherently incorporate the carrier-induced nonlinearities including spatial hole burning and amplitude-phase coupling. We solve the steady-state coupled rate equations and consider the cavity frequency detuning and the individual laser pump rates as the experimentally controlled variables. We show that the carrier-induced nonlinearities play a critical role in the mode control, and we identify gain contrast induced by cavity frequency detuning as a unique mechanism for mode control. Photon-mediated energy transfer between cavities is also discussed. Parity-time symmetry and exceptional points in this system are studied. Unbroken parity-time symmetry can be achieved by judiciously combining cavity detuning and unequal pump rates, while broken symmetry lies on the boundary of the optical locking region. Exceptional points are identified at the intersection between broken and unbroken parity-time symmetry.