Angle of arrival of a focused Gaussian beam in atmospheric turbulence

The angles of arrival (AOA) of plane waves, spherical waves, and focused beams in the geometrical optics limit have been calculated. Since geometrical optics theory allows beams to be focused to an infinitesimal point, the AOA of a focused beam in this limit becomes infinite because of a D^-1/3 dependence of this parameter, where D is the beam diameter. If we apply Gaussian optics theory to this problem, the AOA is no longer infinite at the focal point because the beam size at focus is not infinitely small. In this paper we use Gaussian optics theory to show that the AOA varies according to the diameter and focal length of the focusing element and the wavelength of the radiation being focused, as well as the range. Calculated results are given