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

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? for wavelength ??=?632.8?nm, and the generated focal spot has a full-width-at-half-maximum of about 0.456?, which is smaller than the diffraction limit, 0.54?. A 5?-long longitudinally polarized optical needle with sub-diffraction size is also observed near the designed focal point.

SUBMITTER: Yu AP 

PROVIDER: S-EPMC5150649 | biostudies-literature | 2016 Dec

REPOSITORIES: biostudies-literature