Weak and strong off-axis beam scintillations and beam wander for propagation in turbulence

摘要

We extend the theory of the on-axis beam scintillations for the off-axis case beam points for weak and strong scintillation conditions. Theory is based on the parabolic equation for the beam wave propagation and Markov approximation for the calculation of the statistical moments of the beam intensity. We use the Feynman path integral technique and asymptotic analysis to analyze the dependence of the scintillation index on the distance from the beam axis for collimated beams under weak and strong scintillation conditions. Both strong and weak scintillation cases are considered. Beam scintillation index naturally separates in the uniform (axial) and inhomogeneous (radial) components that can be examined separately. Axial component carries most of the diffractive scattering effects whereas the radial component is mostly related to the pure geometrical perturbation. We examine the contribution of the beam wander to the scintillation index at the different parts of the beam cross section and show that beam wander alone cannot account got the expected magnitudes of the scintillation index.