Phase screen model of turbulent and turbid media for Gaussian beam propagation

Laser-based applications traversing free space are subject to distortions by random refractive index variations that induce optical phase shifts created by optical turbulence and particulates. These volumetric phase shifts can be compressed into a two-dimensional phase map known as a phase screen that can be implemented into wave-optic simulations to predict how a beam will be distorted. This method proves to be effective for modeling atmospheric turbulence and has been extensively explored to treat particulates in previous work. In this work, phase screens including turbulent and turbid media refractive index statistics will be combined and analyzed for Gaussian beam propagation. Optical turbulence will be included using a refractive index power spectrum following the modified atmospheric spectrum to include the effects of a finite inner and outer scale. Scattering by particulates is included using Mie theory to calculate the phase power spectrum to predict the near-forward scattering behavior. A Gamma distribution of particle sizes is chosen to mimic the optical scattering created by fog particles. Quantification will be performed using the Gaussian beam scintillation and the mutual coherence function to understand how optical system parameters are affected. The limitations and complexities of combining the models will be discussed. It is observed that scintillation remains strongly affected by optical turbulence compared to particle scattering in the near-forward direction. The inclusion of particle scattering creates larger intensity losses due to higher angle scattering and blurring of the beam spread function.