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Optics Express

Optics Express

  • Editor: Michael Duncan
  • Vol. 11, Iss. 21 — Oct. 20, 2003
  • pp: 2747–2752

Focusing of doughnut laser beams by a high numerical-aperture objective in free space

Djenan Ganic, Xiaosong Gan, and Min Gu  »View Author Affiliations

Optics Express, Vol. 11, Issue 21, pp. 2747-2752 (2003)

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We report on, in this letter, a phenomenon that the central zero-intensity point of a doughnut beam, caused by phase singularity, disappears in the focus, when such a beam is focused by a high numerical-aperture objective in free space. In addition, the focal shape of the doughnut beam of a given topological charge exhibits the increased ring intensity in the direction orthogonal to the incident polarization state and an elongation in the polarization direction. These phenomena are caused by the effect of depolarization, associated with a high numerical-aperture objective, and become pronounced by the use of a central obstruction in the objective aperture.

© 2003 Optical Society of America

OCIS Codes
(140.7010) Lasers and laser optics : Laser trapping
(180.0180) Microscopy : Microscopy
(260.1960) Physical optics : Diffraction theory

ToC Category:
Research Papers

Original Manuscript: July 31, 2003
Revised Manuscript: October 13, 2003
Published: October 20, 2003

Djenan Ganic, Xiaosong Gan, and Min Gu, "Focusing of doughnut laser beams by a high numerical-aperture objective in free space," Opt. Express 11, 2747-2752 (2003)

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