title: Ultrasmall focusing spot with a long depth of focus based on polarization and phase modulation.
abstract: A design for focusing an incoming light into an ultrasmall spot with a long depth of focus is proposed. We use a phase plate with three concentric regions to modulate the incoming light from radial polarization into outward-inward-outward polarization. The analysis shows that the design is more suitable for a lens with a high numerical aperture because much energy is concentrated in the main lobe of the focus spot.
authors.affiliation: Institute of Optical Sciences, National Central University, Chung-Li 320, Taiwan. ccsun@ios.ncu.edu.tw
authors.forename: Ching-Cherng
authors.initials: CC
authors.lastname: Sun
authors.forename: Chin-Ku
authors.initials: CK
authors.lastname: Liu