Two-parameter study of square-wave switching dynamics in orthogonally delay-coupled semiconductor lasers

Area of Science:

• Physics
• Optics
• Nonlinear Dynamics

Background:

• Semiconductor lasers are crucial for optical communications.
• Understanding polarization switching dynamics is key for laser stability and performance.
• Previous studies explored various coupling schemes, but deterministic square-wave switching remains an area of interest.

Purpose of the Study:

• To conduct a detailed numerical analysis of square-wave (SW) polarization switching in mutually coupled semiconductor lasers.
• To map the dynamics in the coupling strength versus frequency detuning parameter plane.
• To investigate the conditions for stable SWs and their characteristics.

Main Methods:

• Numerical analysis of a system of two semiconductor lasers with time-delayed, orthogonal mutual coupling.
• In-depth mapping of the system's dynamics across a two-parameter plane.
• Identification and characterization of stable square-wave solutions.

Main Results:

• Stable SWs were found in narrow parameter regions near the stability boundary of the pure-mode solution.
• The two coupled lasers emit orthogonal polarizations in the stable SW state.
• Various SW forms exist, and stable switching can occur without noise or nonlinear gain.
• These stable regions are narrow, potentially explaining experimental observations but also posing experimental challenges.

Conclusions:

• Deterministic and stable SWs in coupled semiconductor lasers exist but are confined to very narrow parameter regimes.
• The findings suggest that observed experimental waveforms might be explained by these deterministic SWs.
• Further experimental statistical studies are recommended to distinguish true deterministic SWs from noise-induced long transients.