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Creation of Sub-diffraction Longitudinally Polarized Spot by Focusing Radially Polarized Light with Binary Phase Lens

Author(s): Yu, AP (Yu, An-ping); Chen, G (Chen, Gang); Zhang, ZH (Zhang, Zhi-hai); Wen, ZQ (Wen, Zhong-quan); Dai, LR (Dai, Lu-ru); Zhang, K (Zhang, Kun); Jiang, SL (Jiang, Sen-lin); Wu, ZX (Wu, Zhi-xiang); Li, YY (Li, Yu-yan); Wang, CT (Wang, Chang-tao); Luo, XG (Luo, Xian-gang)
Source: SCIENTIFIC REPORTS  Volume: 6  Article Number: 38859  DOI: 10.1038/srep38859  Published: DEC 12 2016 
Abstract: The generation of a sub-diffraction longitudinally polarized spot is of great interest in various applications, such as optical tweezers, super-resolution microscopy, high-resolution Raman spectroscopy, and high-density optical data storage. Many theoretical investigations have been conducted into the tight focusing of a longitudinally polarized spot with high-numerical-aperture aplanatic lenses in combination with optical filters. Optical super-oscillation provides a new approach to focusing light beyond the diffraction limit. Here, we propose a planar binary phase lens and experimentally demonstrate the generation of a longitudinally polarized sub-diffraction focal spot by focusing radially polarized light. The lens has a numerical aperture of 0.93 and a long focal length of 200 lambda for wavelength lambda = 632.8 nm, and the generated focal spot has a full-width-at-half-maximum of about 0.456 lambda, which is smaller than the diffraction limit, 0.54 lambda. A 5 lambda-long longitudinally polarized optical needle with sub-diffraction size is also observed near the designed focal point.
IDS Number: EE7PX
ISSN: 2045-2322

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