By Peter Weiss
From Long Beach, Calif., at a meeting of the American Physical Society
The light touch of a laser beam can shackle microscopic particles together to make an unusual form of matter. Now, a team of Tennessee researchers finds that this optical binding can set the stage for a chemical encore.
In the late 1980s, scientists at the Rowland Institute for Science and Harvard University, both in Cambridge, Mass., used lasers to create neat arrays of micrometer-size polystyrene beads held together, in part, by photon exchanges. Their new form of matter made headlines but inspired few further studies (SN: 9/30/89, p. 212; 8/18/90, p. 101).
More than a decade later, Andrey Zavalin and Don O. Henderson of Fisk University in Nashville have fabricated so-called optical matter with the hope of eventually using it to create nanometer-scale structures and materials.
In one facet of their vision, the Fisk scientists would harness optically bound arrangements of particles as templates for novel compounds, alloys, or combinations of biomolecules.
Optically cementing particles under the right conditions might encourage chemical or other forces to kick in, the scientists have speculated. “Chemistry in an optical trap is something that just has not been done,” Henderson says.
The researchers make optical matter by shining a laser steadily into a solution of microparticles. They then probe the matter’s properties with ultrashort, 140-femtosecond pulses from a second laser.
Optical matter made of either tiny glass beads or porous mineral bits called zeolites shatters if pulsed within about 30 minutes of being made, the Fisk experiments show. After a longer wait, however, bound zeolites stay intact when pulsed—the first evidence that chemical bonds can take over in optically composed material, Zavalin says.
