On the radiation force fields of fractional-order acoustic vortices

Research output: Contribution to journalLetter (Academic Journal)peer-review

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Abstract

Here we report the creation and observation of acoustic vortices of fractional order. Whilst integer orders are known to produce axisymmetric acoustic fields, fractional orders are shown to break this symmetry and produce a vast array of unexplored field patterns, typically exhibiting multiple closely spaced phase singularities. Here, fractional acoustic vortices are created by emitting ultrasonic waves from an annular array of sources using multiple ramps of phase delay around its circumference. Acoustic radiation force patterns, including multiple concentration points, short straight lines, triangles, squares and discontinuous circles are simulated and experimentally observed. The fractional acoustic vortex leading to two closely spaced phase singularities is used to trap, and by controlling the order, reversibly manipulate two microparticles to a proximity of 0.3 acoustic wavelengths.
Original languageEnglish
Article number14002
Number of pages5
JournalEPL
Volume110
Issue number1
DOIs
Publication statusPublished - 17 Apr 2015

Bibliographical note

Date of Acceptance: 02/04/2015

Keywords

  • acoustic vortices
  • fractional topological charge
  • trap patterns
  • wavelength-scale

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