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Advances in Optical Technologies
Volume 2013 (2013), Article ID 267684, 13 pages
Research Article

Minimizing the Bright/Shadow Focal Spot Size with Controlled Side-Lobe Increase in High-Numerical-Aperture Focusing Systems

Image Processing Systems Institute RAS, Molodogvardeiskaya Street 151, Samara 443001, Russia

Received 8 July 2013; Accepted 13 September 2013

Academic Editor: Augusto Beléndez

Copyright © 2013 S. N. Khonina and S. G. Volotovskiy. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Minimizing the bright/shadow focal spot size for differently polarized incident waves through the additional apodization of the focusing system output pupil by use of an optical element with the vortex phase dependence on angle and the polynomial amplitude dependence on radius is studied. The coefficients of the radial polynomial were optimized with the aim of fulfilling certain conditions such as the energy efficiency preservation and keeping the side lobes under control. The coefficients were chosen so as to minimize the functional using Brent’s method.