Optical trapping and polarization-controlled scattering of dielectric spherical nanoparticles by femtosecond laser pulses

Anwar Usman*, Wei Yi Chiang, Hiroshi Masuhara

*Corresponding author for this work

Research output: Contribution to journalArticle

28 Scopus citations

Abstract

We present optical trapping behavior of 50-nm-sized polystyrene beads, suspended in water medium, by femtosecond pulsed laser beam. In addition to a higher number of nanoparticles trapped at the focal spot by the ultrashort laser pulses compared with that by continuous-wave laser, the nanoparticles are scattered out of the focal spot by the laser pulses to the surrounding area. The scattered particles form a partially opened folding fan-shaped bright locus in two opposite directions, in an alternating manner, perpendicular to the laser polarization. To understand those phenomena, we analyzed radiation (gradient and scattering) force of femtosecond laser pulses and their temporal force exerted on the dielectric spherical nanoparticles by taking into account the impulsive peak power and the axial component of electric light field produced by high numerical aperture of objective lens. We show that the axial electric field is responsible for lateral components of the scattering and temporal forces, and hence, controls the scattering directions of the Rayleigh particles. These findings provide important information about the dynamic optical trapping of the Rayleigh particles by highly focused ultrashort laser pulses.

Original languageEnglish
Pages (from-to)83-90
Number of pages8
JournalJournal of Photochemistry and Photobiology A: Chemistry
Volume234
DOIs
StatePublished - 15 Apr 2012

Keywords

  • Dielectric nanoparticles
  • Lorentz force
  • Optical trapping

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