Light from within
Plasmonic
interferometers that have light emitters within them
could make for
better, more compact biosensors.
Pacifici Lab /
Brown University
(February 10, 2016) A
technique called plasmonic interferometry has the potential to enable compact,
ultra-sensitive biosensors for a variety of applications. A fundamental advance
made by Brown University engineers could help make such devices more practical.
Imagine a hand-held environmental sensor that can instantly
test water for lead, E. coli, and pesticides all at the same time, or a
biosensor that can perform a complete blood workup from just a single drop.
That’s the promise of nanoscale plasmonic interferometry, a technique that
combines nanotechnology with plasmonics—the interaction between electrons in a
metal and light.
Now researchers from Brown University’s School of
Engineering have made an important fundamental advance that could make such
devices more practical. The research team has developed a technique that
eliminates the need for highly specialized external light sources that deliver
coherent light, which the technique normally requires. The advance could enable
more versatile and more compact devices.
“It has always been assumed that coherent light was
necessary for plasmonic interferometry,” said Domenico Pacifici, a professor of
engineering who oversaw the work with his postdoctoral researcher Dongfang Li,
and graduate student Jing Feng. “But we were able to disprove that assumption.”
Plasmonic interferometers make use of the interaction
between light and surface plasmon polaritons, density waves created when light
energy rattles free electrons in a metal. One type of interferometer looks like
a bull’s-eye structure etched into a thin layer of metal. In the center is a
hole poked through the metal layer with a diameter of about 300
nanometers—about 1,000 times smaller than the diameter of a human hair. The
hole is encircled by a series of etched grooves, with diameters of a few
micrometers. Thousands of these bulls-eyes can be placed on a chip the size of
a fingernail.