Optical turbulence model-based imaging analysis employing eddy length scale and refractive index statistics

Abstract

Coherent light propagation in the atmosphere, as occurs with lasers, is significantly impacted by fluctuations in the refractive index of air, which are a function of temperature and pressure. The fluctuations cause beam degradations, including spatial incoherence, power fades, and surges. Conventionally, numerical wave propagation methods with phase screens are used for modeling imaging and optical transmission. Phase screens assume turbulence isotropy and thin turbulence regions to simplify complex turbulence behaviors in the atmosphere. However, these assumptions may result in large deviations due to shear and inhomogeneous regions in the atmospheric boundary layer. An alternate optical turbulence model is proposed using a spherical bubble packing scheme. The broad spectrum of turbulent length scales is represented by the bubbles with radius based on power law distribution based on a linear-eddy model approach. The refractive index of each bubble is prescribed based on the T atarskii spectrum. Imaging is accomplished by a ray tracing algorithm through Snell's law. The effects of length scales, path, and refractive-index structure function coefficient,C 2 n are investigated by imaging analysis. We take several steps to assess model uncertainty and inadequacy for validation and verification. Images generated from ray tracing are used for verification of the bubble model. A numerical wave propagation approach with phase screens is used to validate imaging techniques used on the bubble model with prescribed C 2 n values and profiles.