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Regular dynamics of low-frequency fluctuations in external cavity semiconductor lasers
R L Davidchack1, Y C Lai, A Gavrielides
1Department of Mathematics and Computer Science, University of Leicester, Leicester LE1 7RH, United Kingdom.
Summary
Low-frequency fluctuations (LFFs) in semiconductor lasers arise from quasiperiodic bifurcations, not chaos. Periodic solutions are observed under specific conditions like moderate feedback and large linewidth enhancement factors.
Area of Science:
- Physics
- Optics
- Nonlinear Dynamics
Background:
- Low-frequency fluctuations (LFFs) in external cavity semiconductor lasers are often attributed to stochastic or chaotic dynamics.
- The Lang-Kobayashi (LK) paradigm is commonly used to study LFFs by analyzing external cavity modes.
Purpose of the Study:
- To propose a new framework for understanding LFFs in semiconductor lasers.
- To investigate the role of periodic and quasiperiodic solutions in the LK equations.
Main Methods:
- Analysis of fundamental solutions of the Lang-Kobayashi (LK) equations.
- Numerical simulations and heuristic arguments to explore dynamical behavior.
- Investigation of quasiperiodic bifurcations from periodic solutions.
Main Results:
- Identified periodic or quasiperiodic solutions characterized by time-locked pulses with slowly varying magnitudes.
- Demonstrated that LFFs emerge from quasiperiodic bifurcations as pumping current increases.
- Determined conditions for observing regular periodic solutions: moderate feedback, sub-threshold pumping, and large linewidth enhancement factor.
Conclusions:
- LFFs in semiconductor lasers can originate from quasiperiodic bifurcations of periodic solutions, challenging the purely stochastic/chaotic view.
- The study provides a new perspective on the fundamental dynamics governing LFFs in external cavity semiconductor lasers.