Simulation of wave propagation through turbulent media utilizing the split-step beam propagation method incorporating light attenuation due to aerosol scatter

Abstract

Wave optics simulations study the effect of beam propagation through the atmosphere; one notable method is the splitstep beam propagation method. Current atmospheric propagation software utilizes an alternating series of Fresnel propagation and phase accumulation methods through screens which are statistically representative of the atmospheric turbulence along a line-of-sight path. From this assumption the scintillation parameter along the laser path relies on an atmospheric structure parameter, 𝐶 𝑛 2 , and is typically measured using a path averaged scintillometer. While this works well for links established in static atmospheric conditions in harsher environments such as high precipitation rates, heavy fog, or clouds demand a more rigorous approach. Thus, current software typically over-predicts beam performance of links in harsh conditions. This work proposes a model in which scattering is computed from a "first principles" approach, i.e. the full Mie series is calculated at several locations along the simulated beam path. The scattering results are then combined with the traditional split-step beam propagation method through a correction factor to provide a model of attenuation on beam performance. Results show that the addition of the extinction efficiency factor reduced the overall intensity on target by a significant margin as compared to the traditional split-step beam propagation method. More work is needed to verify the utilization of the Mie scattering extinction along with the log-amplitude variance typically utilized to model the turbulence phase.