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New technique could aid development of nanoscale biosensors
Plasmonic interferometers that have light emitters within them could make for better, more compact biosensors for a variety of applications.
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Researchers at Brown University’s School of Engineering have made an important fundamental advance that could make nanoscale plasmonic interferometry, a technique that combines nanotechnology with plasmonics -- the interaction between electrons in a metal and light, more practical. Plasmonic interferometry has the potential to enable compact, ultra-sensitive biosensors for a variety of applications.
The Brown team, led by Domenico Pacifici, a professor of engineering who oversaw the work with his postdoctoral researcher Dongfang Li and graduate student Jing Feng, has developed a technique that eliminates the need for highly specialized external light sources that deliver coherent light -- beams in which light waves are parallel, have the same wavelength and travel in-phase (meaning the peaks and valleys of the waves are aligned) -- which plasmonic interferometry normally requires. Without coherent light sources, the interferometers cannot produce usable interference patterns. But those kinds of light sources tend to be bulky, expensive, and require careful alignment and periodic recalibration to obtain a reliable optical response.
In the new method developed by Pacifici and his group, fluorescent light-emitting atoms are integrated directly within a tiny hole in the center of the interferometer. An external light source is still necessary to excite the internal emitters, but it doesn't have to be a specialized coherent source.
"This is a whole new concept for optical interferometry," said Pacifici, "an entirely new device."
"It has always been assumed that coherent light was necessary for plasmonic interferometry," adds Pacifici. "But we were able to disprove that assumption." The advance could enable more versatile and more compact devices.
This research was supported by National Science Foundation (NSF) grant CBET 11-59255.
To learn more about this research, see the NSF News From the Field story Advance could aid development of nanoscale biosensors. (Date image taken: 2016; date originally posted to NSF Multimedia Gallery: July 12, 2016)
Credit: Pacific Lab/Brown University
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