"What you end up with is a very small optical spot that you could scan to make detailed images of molecules and other nano-particles," says Kino, the W.M. Keck Foundation Professor of Electrical Engineering, Emeritus. "Normally we use lenses to focus, but it's not possible to resolve detail in objects smaller than one-half the wavelength of light."
Because the shortest wavelength of visible light is 400 nanometers, a conventional microscope cannot resolve objects 200 nanometers or smaller. "But the bowtie antenna produces an optical spot that's 20-nanometers wide, so we're improving the resolution by a factor of 10," Kino says.
Polymers and sensors
In addition to nano-scale optical imaging, Moerner says that bowties may be useful in photopolymerization, a process that uses light to create synthetic compounds (polymers), which researchers can use to trap nano-particles and place them in specific locations. "It's difficult to put molecules and crystals exactly where you want them when you're working at a nano-scale," Schuck explains.
Bowties also may have applications in Raman spectroscopy, a technique that allows scientists to identify individual molecules by measuring the vibrational energy the molecule emits when exposed to light. "It's analogous to fingerprinting," Schuck explains. "Each molecule has a unique vibrational energy, and bowties have a potential use as biological or chemical sensors that can differentiate molecules."
The Stanford team plans to explore these and other practical applications of bowtie nanoantennas in future experiments. On Aug. 30, Moerner will discuss bowties and other developments in the field of nanophotonics at the annual meeting of the American Chemical Society in Washington, D.C.
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Contact: Mark Shwartz
mshwartz@stanford.edu
650-723-9296
Stanford University
30-Aug-2005