Temporal frequency spread of optical wave propagation through anisotropic non-Kolmogorov turbulence

In this paper, we derive new analytic expressions for the atmospheric-induced frequency spread of optical plane and spherical waves propagating in a horizontal path and experiencing anisotropic non-Kolmogorov turbulence. The anisotropic spectrum model is based on the assumption that circular symmetry is maintained in the orthogonal xy-plane throughout the path and that it includes the same degree of anisotropy along the direction of propagation for all the turbulence cell sizes. These expressions are developed in the weak fluctuation region using the Rytov approximation method and are independent of the knowledge of the temporal mutual coherence function for the optical waves. We perform our analysis based on a generalized von Karman power spectrum of the index of refraction. The spectrum considers the effect of finite inner and outer scales of turbulence, together with a non-Kolmogorov spectral power exponent α that varies between 3–4. The simulation results show that the anisotropic parameter impacts on the frequency spread by a factor ${\zeta }^{2-\alpha }$. Moreover the frequency spread is most significant for α values around 3.1. (paper)