Weak and strong off-axis beam scintillations and beam wanderfor 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 strongscintillation conditions. Theory is based on the parabolic equation for the beam wave propagation and Markovapproximation for the calculation of the statistical moments of the beam intensity. We use the Feynman path integraltechnique and asymptotic analysis to analyze the dependence of the scintillation index on the distance from the beamaxis for collimated beams under weak and strong scintillation conditions. Both strong and weak scintillation cases areconsidered. Beam scintillation index naturally separates in the uniform (axial) and inhomogeneous (radial) componentsthat can be examined separately. Axial component carries most of the diffractive scattering effects whereas the radialcomponent is mostly related to the pure geometrical perturbation. We examine the contribution of the beam wander tothe scintillation index at the different parts of the beam cross section and show that beam wander alone cannot accountgot the expected magnitudes of the scintillation index.