Diffraction elimination of slow images

All classical wave fields are subjected to diffraction throughout their propagation. In many systems, a reduction or elimination of the diffraction spreading of beamlike fields are obtained by manipulating the susceptibility in real space and inducing a gradient of the index of refraction. Similarly to wave-guiding, only specific modes may propagate in the induced wave-guides without diffraction or, equivalently, images are revived after a certain self- imaging distance. However in these schemes, diffraction is not suppressed for an arbitrary image and for any distance along the propagation direction.