Gaussian beam weak scintillation: low-order turbulence effects and applicability of the Rytov method

Area of Science:

• Optical physics
• Atmospheric optics
• Wave propagation

Background:

• Laser beam propagation through atmospheric turbulence causes intensity fluctuations (scintillation).
• Existing models like Rytov theory are limited, especially for non-log-normal irradiance distributions.
• Low-order turbulence (LOT) effects like beam wander and breathing are significant but often simplified.

Purpose of the Study:

• Develop a computationally efficient model for irradiance fluctuations in weak turbulence.
• Accurately describe scintillation statistics for Gaussian beams, including non-log-normal behaviors.
• Provide a hybrid model combining LOT and Rytov theories for improved accuracy.

Main Methods:

• Developed a generally applicable description of irradiance fluctuations using single scattering from LOT phase fluctuations.
• Analyzed the LOT solution's accuracy against exact solutions for specific beam and turbulence parameters.
• Formulated a hybrid model by combining the LOT solution with Rytov perturbation theory.
• Validated the hybrid model against wave optics simulation data.

Main Results:

• The LOT solution accurately describes coarse irradiance fluctuations like beam wander and breathing.
• For specific conditions (e.g., focused beams, ground-to-space paths), LOT closely approaches exact solutions, outperforming Rytov theory.
• The hybrid LOT-Rytov model provides accurate scintillation predictions across various irradiance behaviors in weak turbulence.
• Hybrid model predictions show excellent agreement with wave optics simulations.

Conclusions:

• The developed LOT model offers an efficient description of specific scintillation effects.
• A hybrid approach combining LOT and Rytov theories overcomes limitations of individual models.
• This hybrid model enhances the accuracy and applicability of scintillation predictions in atmospheric optics.