Generation of diffracting and non-diffracting speckles

We have generated and propagated both diffracting and non-diffracting speckles using the scattering of perfect optical vortices. The diffracting speckles have been realized in the near field and non-diffracting speckles have been realized in the far field, i.e. after taking the Fourier transform of near-field speckles using a simple convex lens. We found that the experimental results are in good agreement with the theoretical results. These results may find applications in classical cryptography and communication as we have both varying and non-varying random field patterns with propagation distance.