Journal
OPTICS EXPRESS
Volume 18, Issue 21, Pages 21965-21972Publisher
OPTICAL SOC AMER
DOI: 10.1364/OE.18.021965
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- Nanjing University of Aeronautics and Astronautics [NS2010200]
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We report a new method to create high purity longitudinally polarized field with extremely long depth of focus in the focal volume of a high numerical aperture (NA) objective lens. Through reversing the radiated field from an electric dipole array situated near the focus of the high-NA lens, the required incident field distribution in the pupil plane for the creation of an ultra-long optical needle field can be found. Numerical examples demonstrate that an optical needle field with a depth of focus up to 8 lambda is obtainable. Throughout the depth of focus, this engineered focal field maintains a diffraction limited transverse spot size (<0.43 lambda) with high longitudinal polarization purity. From the calculated pupil plane distribution, a simplified discrete complex pupil filter can be designed and significant improvements over the previously reported complex filters are clearly demonstrated. (C) 2010 Optical Society of America
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