Turbulence hierarchy in a random fibre laser

Area of Science:

• Photonics
• Complex Systems
• Statistical Physics

Background:

• Turbulence is a complex phenomenon observed across various scientific disciplines.
• Random fiber lasers offer a unique, cavity-less platform for studying light propagation in disordered media.
• Understanding intensity fluctuations in these lasers is crucial for their application and fundamental physics.

Purpose of the Study:

• To investigate statistical signatures of turbulence in the intensity fluctuations of a continuous-wave-pumped erbium-based random fiber laser.
• To analyze the distribution of intensity fluctuations across different operational regimes (below, near, and above threshold).
• To develop and validate a theoretical model explaining the observed turbulent behavior.

Main Methods:

• Utilized an erbium-based random fiber laser with random Bragg grating scatterers.
• Collected extensive data on laser intensity fluctuations under continuous-wave pumping.
• Analyzed the statistical distributions of intensity fluctuations, including Gaussian, exponential, and stretched-exponential tails.
• Applied a hierarchical stochastic model incorporating Kolmogorov's theory of turbulence.

Main Results:

• Observed three distinct regimes of intensity fluctuation distributions: Gaussian below threshold, a mixture of distributions with exponential tails near threshold, and stretched-exponential tails above threshold.
• Demonstrated that these distributions are well-described by a hierarchical stochastic model.
• The model successfully incorporates concepts of energy cascade and intermittency from Kolmogorov's turbulence theory.

Conclusions:

• Random fiber lasers exhibit statistical turbulence signatures in their intensity fluctuations.
• A hierarchical stochastic model, grounded in Kolmogorov's turbulence theory, effectively explains these phenomena.
• This work provides a novel experimental platform for studying turbulence in photonics and complex systems.