Effects of atmospheric turbulence on the transmission of a laser beam at 6328 A. II-frequency spectra.

The frequency spectra of light intensity fluctuations of a laser beam by atmospheric turbulence were investigated using a He-Ne gas laser at 6328 A with a beam diameter of about 3.5 mm and optical path length of L = 4.5 km and 14.5 km. The normalized spectra U(f) were not systematically affected by different receiving aperture diameters 5 mm <or= D <or= 80 mm, probably because of the small diameter of the output aperture of the source. The theoretical relation f(c) L(-1/2), where f(c) is a characteristic frequency of U(f), does not appear to hold empirically.