Near-field speckles produced by random self-affine surfaces and their contrast transitions

Anisotropy of near-field speckle patterns

In the vicinity of a rough interface under normal illumination the speckle field has been found to be anisotropic; that is, its correlation length is much larger in the direction of polarization than in the perpendicular direction, forming stripe-shaped speckle patterns in the near-field region. Furthermore, with increasing distance from the interface, the anisotropy of the near-field speckles decays rapidly, while the speckle size increases drastically in all directions. Based on detailed analysis, it was found that the anisotropy of the near-field speckle patterns can be attributed to polarization-dependent coupling among the evanescent waves from different surface diffusers.