Propagation of Laguerre–Gaussian beams in anisotropic atmospheric turbulence: analysis via two analytical and a computational method

Propagation of an orbital angular momentum beam-the Laguerre-Gaussian (LG) beam-through anisotropic non-Kolmogorov atmospheric turbulence is analyzed using three approaches: the extended Huygens-Fresnel (EHF) principle, the perturbation method, and computational wave-optics simulations (WOS). Two LG beams (modes 1 and 2) are evaluated on how their characteristics change with varying turbulence parameters. Beam irradiance profiles and spot sizes are computed, with the goal of assessing the relative stability of different modes. For the Kolmogorov power-law exponent, the results obtained via the perturbation method show good agreement with those from the EHF principle and WOS but only within the weak-to-moderate fluctuation regime. For stronger turbulence fluctuations, the results obtained via the perturbation method begin to deviate, whereas the EHF principle and WOS remain in good agreement. It is also shown that this type of alignment does not hold in other power-law exponents. Results obtained by the EHF principle and WOS show both the LG modes exhibit deformation under turbulence, though the lower-order mode shows a more pronounced rate of change, and the higher-order mode remains more confined and symmetric. The results obtained by the perturbation method are confirmed or rejected in different scenarios. Results obtained for two LG beams, and via all three methods, show saturation of the degree of ellipticity after some anisotropy ratios.