Creating light tweezers for particle manipulation

Overview

Topic status: We're looking for students to study this topic.

Australian researchers are breaking new ground by developing new techniques and methodologies to fabricate nanostructured materials for a diverse range of applications. One of the holy grails of this research effort is to create miniature machines with dimensions less than a 1 um that perform complicated functions like determine whether tissue is cancerous or not and destroy it if it is. These smart materials will revolutionize many industries. One significant problem faced by the fabricators and users of these nanomaterials is how to properly handle such small, usually fragile, structures. Most conventional physical means such as tweezers are simply too large and would damage the structure. Some form of non-contact manipulation is the only viable option.

For over 20 years researchers have been using laser light to slow, trap, cool, and manipulate particles1. This is possible as the interaction between the light and particles depends on the intensity of the light. Therefore, by controlling the spatial properties of the illuminating beam, a particle can be confined to a specific region of the laser beam. A classic demonstration of this effect is observed when particles are manipulated with a TEM01* 'doughnut mode' Gaussian laser beam shown in figure 1. This beam has a region of low intensity at the centre of the beam. Any suitable particle entering the beam is forced into the 'null' at the centre and because of the gradient force that the light exerts, the particle remains there while the laser beam is on.

The aim of this project is to create doughnut mode laser beams, using holography2. Much of the work will focus on designing and fabricating the hologram necessary to generate the doughnut mode. The work will also include generating other user defined laser fields such as a radially polarized light beam for particle manipulation.

The project will include a combination of electromagnetic theory, and laser physics. The holograms will be theoretically designed, using established laser and optical methods and then fabricated professionally. Characterization will be undertaken in FaSTs laser physics laboratory.

References:

  • Ashkin, 'Optical trapping and manipulation of neutral particles using lasers', PNAS 94, p4853 (1997)
  • N. Heckenberg, R. McDuff, C. P. Smith, A. G. White, 'Generation of optical phase singularities by computer generated holograms', Opt. Lett. 17 p221 (1992)
Study level
Honours
Supervisors
QUT
Organisational unit

Science and Engineering Faculty

Research area

Physics

Contact
Please contact the supervisor.