Splitting of the focal spot of a high numerical-aperture objective in free space

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Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/1947

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Title: Splitting of the focal spot of a high numerical-aperture objective in free space
Author(s): Chon, James W. M.; Gan, Xiaosong; Gu, Min
Abstract: Reported in this letter is a phenomenon that the focal spot of a high numerical-aperture objective in free space can split into two spots if a ring beam is used for illumination. Diffraction by a high numerical-aperture objective results in a depolarization such that the diffracted field in the focal region includes not only a component with the same polarization as the incident beam, but also orthogonal and longitudinal components. The use of a ring beam enhances the relative contribution from the longitudinal component. As a result, a single focal spot splits into two spots along the incident polarization direction. It is revealed theoretically that for an objective of given numerical aperture there is a threshold of the central obstruction size of a ring beam for the appearance of a two-peak focus.
Publication type: Journal article
Research centre: Swinburne University of Technology. School of Biophysical Science and Electrical Engineering
Source: Applied physics letters, Vol. 81, no. 9 (2002), pp. 1576-1578
Publication year: 2002
Keyword(s): Lenses; Optical focusing; Light diffraction; Light polarisation
Publisher: American Institute of Physics
ISSN: 0003-6951
Publisher URL: http://dx.doi.org/doi:10.1063/1.1501442
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