Tweezers Employ Three Forces

Using a Michelson interferometer in a double-hologram setup, researchers at Nanyang Technological University in Singapore have demonstrated a new type of optical tweezers based on the interference of Laguerre-Gaussian beams. The system, which is more compact than those that employ a Mach-Zehnder configuration, enables the trapping and manipulation of microparticles by the optical gradient force, spin angular momentum and orbital angular momentum.

Reporting in the Feb. 10 issue of Optics Express, the researchers describe how they produced interference patterns with a 632.8-nm HeNe laser and an optical setup incorporating one or two computer-generated holograms. They suggest that the optical tweezers will enable investigations by physicists into the force interaction of laser beams as well as offer a means of inducing dual rotation in biological samples.