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Coarse grained variables and deterministic chaos in an excitable system.

Jhon F Martinez Avila¹, Hugo L D de S Cavalcante, J R Rios Leite

¹Departamento de Física, Universidade Federal de Pernambuco, 50670-901 Recife, PE, Brazil.

Physical Review Letters

|March 21, 2008

Summary

Semiconductor lasers with optical feedback exhibit self-excitable dynamics, replacing external noise with internal chaotic oscillations. This study defines a phase space to measure spike recovery and drop times in these systems.

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Area of Science:

Physics
Nonlinear Dynamics
Laser Physics

Background:

Semiconductor lasers with optical feedback are prone to complex dynamics.
Low-frequency fluctuations (LFFs) are a common chaotic behavior observed in these systems.
Understanding the underlying mechanisms of LFFs is crucial for laser stability and applications.

Purpose of the Study:

To investigate the self-excitable nature of chaotic low-frequency fluctuations in semiconductor lasers with optical feedback.
To replace the concept of external exciting noise with intrinsic ultrafast chaotic oscillations.
To define a low-dimensional phase space and characterize the dynamics of LFF spikes.

Main Methods:

Application of temporal coarse graining to the dynamical variables of a semiconductor laser with optical feedback.
Numerical and experimental analysis of chaotic low-frequency fluctuations.
Definition of a low-dimensional coarse-grained phase space.
Introduction and measurement of time constants for spike decay and recovery.

Main Results:

Chaotic low-frequency fluctuations in semiconductor lasers with optical feedback demonstrate properties of a self-excitable deterministic system.
Ultrafast chaotic oscillations within the system effectively replace external exciting noise.
A low-dimensional phase space was successfully defined for characterizing the system's dynamics.
Time constants characterizing the exponential drop and recovery of equally shaped spikes were measured.

Conclusions:

The study confirms the self-excitable nature of chaotic LFFs in semiconductor lasers with optical feedback.
Internal chaotic oscillations play a key role in driving the system's dynamics, mimicking external excitation.
The developed coarse-grained phase space and measured time constants provide valuable insights into the spike dynamics of these lasers.