Experimental investigation of fluctuations of a laser beam in an atmospheric path

A method was developed for measuring the principal parameters of a laser beam traveling in the atmosphere. In this method it was assumed that the transverse distribution of the intensity in a beam was Gaussian so that these parameters could be determined from the results of measurements of the intensity at three points in a transverse cross section of a beam. The results were subjected to a computer analysis which yielded the integrated intensity of the beam, its radius and position of the center, distribution of the probabilities, and frequency spectra of these parameters. The measurements carried out at wavelengths of 0.63 and 10.6 μ over a city path 5.2 km long demonstrated that under these conditions the fluctuations of the beam parameters were very similar at these two wavelengths.