title: Enlightening darkness to diffraction limit and beyond: comparison and optimization of different polarizations for dark spot generation.
abstract: We compare generation of a dark spot using focusing of beams with azimuthal polarizion, radial polarization with a vortex, and a circular polarization with either a first or second order vortex. By optimization of the amplitude-phase pupil, it is ascertained that azimuthal polarization is the most suitable one to obtain the diffraction bounded dark spot per se whose scalar approximation limit has FWHM=0.29λ. Consequently, for dark spot generation, this polarization plays the role of the radial polarization in creation of the diffraction-limited bright spot. Using azimuthal polarization, it is shown that an amplitude-phase filter allows generation of a subdiffractive dark spot in a prescribed finite area.
authors: Image Processing Systems Institute of the Russian Academy of Sciences, Samara, Russia. khonina@smr.ru
authors: Svetlana N
authors: SN
authors: Khonina
authors: Ilya
authors: I
authors: Golub