Fluctuating Properties of Gaussian Light Beams in an Atmosphere
Fluctuations of a Gaussian light beam propagating through an atmosphere, whose refractive index inhomogeneities are assumed to obey the Kolmogorov's law, are discussed statistically from the viewpoint of mode conversion. The results obtained here are concerned with the dependence of the mode conversion on beam shape parameters (beam spot size and radius of wave front curvature), propagation distance, and medium turbulence features. The mode conversion increases proportionally to the propagation distance z in the near-field region of a transmitting aperture and then to 8/3 powers of z in the far-field region. The mode conversion also increases according to 5/3 powers of the beam spot size s at a short distance, while it decreases for a large spot size at a long distance. Studies on wave front curvature are also done. Near the focal point of a focused beam, the reduction effect of the mode conversion appears.