Log-intensity correlations of a laser beam in a turbulent medium

The log-intensity correlation for any two points in the cross section of a collimated Gaussian laser beam is calculated in the geometrical optics approximation. The log-intensity correlation is found to.be a function of more than the separation distance between the two points. The special case of autocorrelation leads to a result that is identical to that given by Ho if diffraction effects are ignored. The autocorrelation function indicates a new method for determining the inner scale of turbulence and the refractive index structure function coefficient which does not depend upon meteorological measurements of C(N)(2).