The zero time-delay degree of second order temporal coherence $g^(2)$(0) is investigated in a dynamic laser speckle backscattered form a uniformly rotating randomly rough aluminium metal surface. The s-polarized laser beam is incident at an angle -30$˚ to the surface and the angular distributions of the mean intensity and $g^(2)$(0) are measured in the incidence plane.
In obtaining $g^(2)$(0) from the experimental data, the contribution of the shot noise is subtracted from the photoelectric signal. In the scattered light, both of the s- and p-components of the scattered light are found to be close to the Gaussian light and the measured $g^(2)$(0) is consistent with the theoretical value.
The degree of second order temporal coherence $g_s^(2)(τ)$ of the backscattered light, which has the same polarization with the incident laser beam, is measured. At each scattering angle $θ_s$, $g_s^(2)(τ)$ is almost consistent with the function {1+exp$(-τ^2/τ_c^2)$}, which is the same result with the case of the laser speckle formed by the laser light scattered from the rotating ground glass. There appears a peak in the angular distribution of τc with the maximum at $θ_s = 34˚. It is found that the rough metallic scattering with multiple scattering over than 10% has the same function of the degree of second order temporal coherence with that of the ground glass surface scattering where the multiple scattering is ignorably small.
