Fluctuations of a Gaussian Light Beam Propagating Through a Random Medium

Abstract

Distributions of the log-amplitude and phase fluctuations of a Gaussian light beam propagating through a randomly inhomoe:eneOl!S ml'dium arP. studied by the evaluation of their mean square values. By means of the adequate focusing system (the optical transmitting antenna) of an aperture size lar!!:e compared with the medium turbulence scale, log-amplitude fluctuations are greatly reduced slightly behind the focal point of the focusing system. The reduced fluctuation is strongly dependent upon the focal length, when the focal length is short.

Mode Conversion of Gaussian Light Beams Propagating Through a Random Medium

“…Diffraction losses due to the finite aperture of the optical receiving antenna also increase and serious detection losses may occur, particularly in a heterodyne receiving system. Fried and Seidman [1967] have calculated the mean square log-amplitude fluctuation of a focused beam in the atmosphere with the Kolmogorov power spectrum of the refractive index, and Kinoshita et al [1968] have investigated the fluctuations of log-amplitude and phase of the same Gaussian beam, assuming that the turbulent medium has a Gaussian autocorrelation of the refractive index inhomogeneities. Gloge [1967] has studied the beam scintillation in a shielded opticallense wave guide from the viewpoint of mode conversion, which may be caused by the random surface irregularities of the lens and by the fluctuations of the air between these lenses.…”

Optical Propagation: Problems and Trends

“…, 0 (For spherical waves see, for example, [18], [21] and [22] ; for gaussian beams see, for example, [19] and [25][26][27] .) These are valid in the single scattering approximation .…”