Observation of diffraction multifocal radiation focusing

It is shown experimentally that by placing a flat screen with an axial hole in a diffraction field formed by the first open Fresnel zone upon diffract ion of a plane electromagnetic wave from a parallel screen with a hole of a larger diameter, one can observe diffraction multifocal focusing of radiat ion in the near-field zone of the first screen. The diffraction pattern in the near-field zone of the first screen in focal planes represents circular nonlocalised Fresnel bands with a bright narrow peak at the centre, whose intensity is 6-10 greater than that of the incident wave.