Demonstration of longitudinally polarized optical needles

Research output: Contribution to journalArticleScientificpeer-review

Details

Original languageEnglish
Pages (from-to)27572-27584
Number of pages13
JournalOptics Express
Volume26
Issue number21
Publication statusPublished - 15 Oct 2018
MoE publication typeA1 Journal article-refereed

Researchers

  • Léo Turquet
  • Xiaorun Zang
  • Joona Pekko Kakko
  • Harri Lipsanen

  • Godofredo Bautista
  • Martti Kauranen

Research units

  • Tampere University of Technology

Abstract

Longitudinally polarized optical needles are beams that exhibit ultra-long depth of field, subwavelength transverse confinement, and polarization oriented along the longitudinal direction. Although several techniques have been proposed to generate such needles, their scarce experimental observations have been indirect and incomplete. Here, we demonstrate the creation and full three-dimensional verification of a longitudinally polarized optical needle. This needle is produced by generating a radially polarized Bessel-Gauss beam at the focus of a high numerical aperture microscope objective. Using three-dimensional spatial mapping of second-harmonic generation from a single vertically aligned GaAs nanowire, we directly verify such a longitudinally polarized optical needle's properties, which are formed at the focus. The needle exhibits a dominant polarization, which is oriented along the longitudinal direction, an ultra-long depth of field (30 λ), and high spatial homogeneity. These are in agreement with corresponding focal field calculations that use vector diffraction theory. Our findings open new opportunities for manipulation and utilization of longitudinally polarized optical needles.

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