Coherence Effects: from Spectral Change to Nondiffraction

We have studied the interference of light produced by a pair of circularly symmetric Collett-Wolf beams, and found that the output radiation from the interferometer in the far-field is a beam with an intensity distribution that displays a narrow bright spot at its center that diverges with the distance from the sources much more slowly than the beam itself. This result suggests that the interference of a pair of symmetric Collett-Wolf beams can be used to produce a pseudo-nondiffracting beam. We have also studied the temporal average over an ensemble of realizations of the output power spectrum of the interference of light produced by a pair of circularly symmetric Collett-Wolf beams, which causes a change in the spectrum of the light as well.