Optical effect of diffractive multifocal focusing of radiation on a bicomponent diffraction system

It is shown for the first time, to our knowledge, that when a plane wave il luminates a certain type of bicomponent optical system, consisting of two p lane screens with circular apertures on a given optical axis, a multifocal diffractive focusing effect can appear. Here the diffraction picture in the focal planes represents the circular nonlocal bands of the Fresnel zones w ith a bright narrow peak at the center, whose intensity can exceed by 6-10 times the value of the incident-wave intensity. The detected optical effect is observed across a wide range of wavelengths, lambda = 0.4-10(3) mu m, a nd ratios of the aperture diameters d(1) greater than or equal to 2d(2) = 2 5-1000 lambda, and it is also insensitive to changes in the medium of the w ave propagation. For the large diameters of input holes, d(1) = 2d(2) > 100 lambda, or for wavelengths in the radio-frequency region of the spectrum, the bicomponent diffraction system acts as a long-focus lens with a high-in tensity Gaussian distribution of radiation, at times exceeding the initial intensity, persisting at large distances (z = 1-100 cm) from the diffractio n system. (C) 2000 Optical Society of America OCIS codes: 050.0050, 050.197 0, 220.3630, 220.2560, 220.4830, 080.5620.