Theoretical and experimental investigations of the effect of diffractive multifocal focusing of radiation

The new optical effect of diffractive multifocal focusing of radiation, pre dicted earlier by theory, on a bicomponent diffraction system with small Fr esnel numbers that consists of two plane screens with circular apertures on given optical axes, is confirmed experimentally. It is shown that the diff raction picture in the focal planes of such a system represents the circula r nonlocal bands of the Fresnel zones with a bright narrow peak at the cent er, whose intensity in the experiment can exceed by six to ten times the va lue of the incident plane-wave intensity. Experimentally it is established that the diffractive multifocal focusing of radiation on real screens with axial circular apertures, whose diameters exceed the radiation wavelength, is insensitive to the rough external conditions: thickness of the screens, irregularities of the edges and nonideal form of the apertures, heterogenei ty of the initial distribution of the incident-wave intensity, and changes in the medium of the wave propagation. (C) 2001 Optical Society of America.