  We experimentally and numerically tested the separability of two independent
equally-luminous monochromatic and white light sources at the diffraction
limit, using Optical Vortices (OV), related to the Orbital Angular Momentum
(OAM) of light. The diffraction pattern of one of the two sources crosses a
phase modifying device (fork-hologram) on its center generating the
Laguerre-Gaussian (L-G) transform of an Airy disk. The second source, crossing
the fork-hologram in positions different from the optical center, acquires
different OAM values and generates non-symmetric L-G patterns. We formulated a
criterion, based on the asymmetric intensity distribution of the superposed L-G
patterns so created, to resolve the two sources at angular distances much below
the Rayleigh criterion. Analogous experiments carried out in white light allow
angular resolutions which are still one order of magnitude below the Rayleigh
criterion. The use OVs might offer new applications for stellar separation in
future space experiments.
