Diffuse reflections by randomly gradient index metamaterials.

We have demonstrated that a thin planar coating with randomly distributed index gradients can create diffuse reflections in front of a planar conducting sheet. This scheme is verified by two-dimensional near-field scanning measurement, in which the randomly gradient index coating is implemented by periodic crossed-I-shaped array whose unit cell's dimension varies spatially. Some qualitative principles of choosing the distribution mode of random index gradient are presented.