In the speckle, backscattered to the far field from the randomly rough metal surface, the effect of the multiple scattering on the intensity correlation $g^{(2)}(τ)$, with correlation time τ was investigated.
The s- polarized (perpendicular to the incidence plane) laser beam is incident with the incidence angel of -30 degree on the ground surface of the slowly rotating ground glass. The ground glass was aluminium coated, and the angular distribution of both the mean intensity ＜Ⅰ＞ and $g^{(2)}(τ)$ of the dynamic speckle were measured in the incidence plane. Mean intensities and intensity correlations of both s- and p- polarized components were also measured, which are $＜Ⅰ_s＞$, $＜Ⅰ_p＞$ $g^{(2)}_s(τ)$, and $g^{(2)}_p(τ)$ respectively.
$＜Ⅰ_p＞$ is significant in the amounts and has the local peak in the antispecular direction. Intensity fluctuation $g^{(2)}$(0) i.e., $g^{(2)}(τ)$ with τ equal to zero is found less than 2 in the Gaussian scattering region where a large number of scatterers contribute in the formation of speckle, and less than $g^{(2)}_s(0)$ in all the scattering region. And $g^{(2)}$(τ) with non-zero τ is almost the same as $g^{(2)}_s(τ) in all the scattering region.
The theory with the multiple scattering taken into account, was developed on the assumption that the surface can be regarded as a group of independent scatterers, some of which give single scattering, and the others multiple scattering.
The formula of $g^{(2)}$(τ) derived for both zero and nonzero τ in the Gaussian scattering region, is in good agreement with the experimental $g^{(2)}$(τ) based on the experimental values of $＜Ⅰ_p＞/＜Ⅰ_s＞$, $g^{(2)}_s(τ)$, $g^{(2)}_p(τ)$. The application of the formula derived in the non-Gaussian scattering region, to the determination of the number of scatterers was also discussed.
