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 nearfield speckle patterns can be attributed to polarization-dependent coupling among the evanescent waves from different surface diffusers.