We study by computer simulations the initial stage of bright background beam self-focusing initiated by the energy density redistribution due to the presence of optical vortex and/or ring dark wave. Local self-focusing Kerr nonlinear medium is considered. When a single ring dark wave is nested on the background, ring radius-to-width ratio Δ=2 promises up to 4 times peak intensity increase at a propagation distance of 2 dark beam diffraction lengths. Δ=6 seems adequate when flat-toped super-Gaussian beam is desired. Self-focusing in bright rings of different radii and even in two coaxial rings (at Δ=3) is observed when initially optical vortex and ring dark wave are simultaneously nested on the background. The detailed numerical analysis of the evolution of azimuthal perturbations confirmed the physical intuition that self-focusing rings of small radii suffer much less (when at all) from ring filamentation, because the spatial frequency of the perturbations on the inner rings appear higher than the critical one.

Date Published: 15 March 2013
PDF: 8 pages
Proc. SPIE 8770, 17th International School on Quantum Electronics: Laser Physics and Applications, 87701H (15 March 2013); doi: 10.1117/12.2012434

Published in SPIE Proceedings Vol. 8770:
17th International School on Quantum Electronics: Laser Physics and Applications
Tanja N. Dreischuh; Albena T. Daskalova, Editor(s)