An integral expression is evaluated for the log-amplitude mean value of a gaussian or laser-like optical beam propagating along a horizontal path in a turbulent atmosphere. The mean-value integral expression has been taken from an analysis by Schmeltzer for a gaussian beam in the atmosphere. The expressions presented here for the log-amplitude mean value depend on the product of a strength factor, which is the log-amplitude variance for a point source, and a multiplying factor that depends on the source beam size. Numerical results for the beam-size-dependent factor are given for a wide range of beam sizes, wavelengths, and path lengths. Numerical results are also presented for the mean on-axis irradiance and mean beam size, for focused and collimated gaussian beams. These will find application in the design of systems for laser communication in the atmosphere. The data are obtained by combining our results for the log-amplitude mean with published data for the variance. The integral expression used here for the log-amplitude mean value is based on an assumption which restricts the range of validity of our results. The conditions necessary for its validity are discussed.
© 1969 Optical Society of AmericaPDF Article