An investigation of the degradation of a laser beam by high intensity turbulence

The reduction of intensity of the far field central spot formed by a collimated laser beam traversing high intensity turbulences near the laser source was correlated with the statistical behavior of the turbulence generated refractive index perturbations causing the intensity reduction. An analytical method to predict the intensity degradation using statistical turbulence parameters was developed. The variables in analytical relation were laser beam diameter and wave number, path length of turbulence traversed, and structure functions of traversed refractive index perturbations. Since refractive index perturbations could not be readily measured a method to approximate these perturbations, via the equations of state, using temperature and velocity perturbation correlation functions was developed. An experiment to measure the actual far field central spot intensity reduction and the temperature and velocity perturbations causing that reduction was conducted.