Optical Tractor Beam

July 25, 2011

A touch of Star Trek from the original research literature…

Physicists from Shanghai’s Fudan University and The Hong Kong University of Science and Technology have shown that, at least in the microscopic world, optical beams could exert a pulling force on tiny spherical particles.

Light carries momentum, so it can push an object forward by scattering off its surface. But if the direction of scattering could be reversed, a pulling force or ‘tractor beam’ should result. The researchers calculate that, using laser beams with specially tailored intensity profiles, it is possible to exert a pulling force on polystyrene beads. The effect occurs for a few select particle sizes (around 4 microns in diameter) and should extend to other dielectric materials.

The results may aid optical micromanipulation techniques, for example in studying biomolecules or nanoparticle sorting.

Source: Nature Photonics 5, 531–534 (2011) doi:10.1038/nphoton.2011.153