Laser tweezer grabs varied specks

Researchers have used optical tweezers for several years to trap and manipulate microscopic objects. The tweezers are laser beams that are intense enough to move microscopic objects much like wind moves everyday objects.

Researchers from Riso National Laboratory in Denmark have advanced the use of optical tweezers with a method that allows them to simultaneously trap and independently manipulate microscopic materials that have different indices of refraction. This will allow researchers to work with mixes of materials like particles and air bubbles.

The method could also lead to light-powered and controlled labs-on-a-chip, dynamically reconfigurable micro-optics, and light-controlled reconfigurable photonic crystal arrays. Micro-optics are tiny mirrors and lenses commonly used in telecommunications; photonic crystal is porous or varied material that channels light in very small spaces.

There are two basic types of optical tweezers -- holographic and phase contrast. The Riso National Laboratory method uses the simpler phase contrast method, which maps dynamic spatial light modulator patterns in a fairly straightforward way, requires less compute power, and allows for differently shaped beams, according to the researchers.

The researchers are using the method to study cell interactions. The work appeared in the April 5, 2004 issue of Optics Express.