Spiral laser beam demoed

Researchers have for years used light to move and manipulate tiny particles; the energy in a light beam affects particles like cells in the same way wind affects larger objects.

Researchers from the University of the Philippines and Risø National Laboratory in Denmark have found a way to generate helico-conical, or spiral-shaped light beams. The unusual-shaped beams are potentially useful in trapping and manipulating particles in biological and medical devices, including biochips.

The researchers generated the spiral light beams using a liquid crystal spatial light modulator, which is like a liquid crystal display that shapes laser beams passing through it. The researchers merged corkscrew- and cone-shaped lightwaves to produce the spiral beam. Corkscrew lightwaves have a ring-shaped cross-section; the researchers' beams have a spiral cross-section.

The next steps are implementing the spiral beam in a high-power optical trap to test the way the beam interacts with microparticles. The technique could be used to rotate asymmetrical particles and to sweep small particles toward the beam's focal point. The researchers are also working to more fully understand the dynamics of the spiral beams.

The spiral lightwaves could be used practically within a year, according to the researchers. The work appeared in the March 7, 2005 issue of Optics Express (Helico-Conical Optical Beams: a Product of Helical and Conical Phase Fronts).