Experimental study on the existence and properties of speckle phase vortices in the diffraction region near random surfaces.

We design an optical setup to extract phase vortices in which the interference intensity of reference light wave and speckle fields produced by random screens with different roughness values in the diffraction region near random screens is obtained. Random screens with different roughness are used as samples. Fourier transform is used to extract speckle phase vortices from the interference intensity, and the experimental results show that the phase vortices can be produced when the roughness of the screen is large enough, and they even may appear on the surface. The density of phase vortices would become larger with an increase of the distances in the diffraction region near the random screen. When the distance is certain, the density of phase vortices becomes larger with the increase of roughness. These results would be helpful for understanding the formation of phase vortices.