Self-reconstruction of a Bessel beam in a nonlinear medium

It is observed that by blocking more than 80% of the azimuth of the aperture of a Bessel beam, a full 360 degrees far-field ring is reconstructed after the beam passes through a liquid. The reconstruction has a power threshold and is preceded by stimulated Rayleigh-wing scattering along the Bessel beam cone axis. The phenomenon is explained in terms of longitudinally phase matched, inverse stimulated Rayleigh wing scattering. A Raman-shifted conical emission is also observed and interpreted as diffraction of the on-axis Raman Stokes beam from an additional, spatially periodic index modulation which is due to interference of the Bessel pump beam with the on-axis Rayleigh wing Stokes beam.