Exploring the propagation of Gaussian and Laguerre-Gaussian beams in anisotropic atmospheric turbulence: implications for beam ellipticity and turbulence-dependent effects

The propagation of optical beams through the atmosphere has been extensively studied due to its applications in fields such as communication, imaging, and remote sensing. Among the various types of beams, the commonly used Gaussian beam and beams carrying orbital angular momentum (OAM), are of particular interest. The ability of Laguerre-Gaussian (LG) beams to encode information in their OAM modes makes them interesting for optical communication applications. While most studies consider isotropic turbulence, the more realistic scenario involves anisotropic turbulence. This occurs in boundary conditions near hard surfaces (the ground), where external forces such as wind shear or thermal gradients alter the form of eddy currents, affecting refractive index fluctuations, and introducing directional dependencies into the problem. Understanding LG beam propagating through the atmosphere under such anisotropic conditions is crucial for optimizing performance in practical applications. These beams are particularly sensitive to turbulence, which can degrade their OAM modes, disrupt multiplexing schemes in free space optical communications, or reduce the fidelity of transmitted data. A theoretical and numerical approach was used to provide insights into the effects of turbulence-induced distortions of Gaussian and LG beams propagating in turbulent environments. The beam's intensity profile and spot size and its degree of ellipticity are obtained, and the effect of different contributing parameters of turbulence such as generalized structure function, inner scale, anisotropy, and power-law exponent for the refractive index spatial frequency power spectrum are investigated.