Plasmonics: Squeezing light into metals

ELECTRICAL engineers at the University of Utah have used an inexpensive, commercial inkjet printer to produce microscopic structures that use light in metals to carry information. This new technique, called “plasmonics”, controls electrical conductivity within such microstructures, which could be used to rapidly fabricate superfast components in electronic devices, make wireless technology faster or print magnetic materials.

University of Utah electrical engineers Ajay Nahata (left) and Barun Gupta used a $60 inkjet printer with silver and carbon ink cartridges to create a new, widely applicable way to make microscopic structures that use light in metals to carry information in electronic devices, make wireless technology faster or print magnetic materials ( Dan Hixson, University of Utah College of Engineering) 

The study appeared online March 7 in the journal Advanced Optical Materials.

Plasmonics marries the best aspects of optical and electronic data transfer. By crowding light into metal structures with dimensions far smaller than its wavelength, data can be transmitted at much higher frequencies such as terahertz frequencies. Metals such as silver and gold are particularly promising plasmonic materials because they enhance this crowding effect.

Terahertz frequencies lie between microwaves and infrared light on the spectrum of electromagnetic radiation that also includes everything from X-rays to visible light to gamma rays.
“Very little well-developed technology exists to create terahertz plasmonic devices, which have the potential to make wireless devices such as Bluetooth – which operates at 2.4 gigahertz frequency – 1,000 times faster than they are today,” said Ajay Nahata, a professor of electrical and computer engineering at the University of Utah College of Engineering and senior author of the new study.

Controlling conductivity

Plasmonic arrays are currently made using microfabrication techniques that require expensive equipment and manufacture only one array at a time. Until now, controlling conductivity in these arrays has proven extremely difficult for researchers.

“Using a $60 inkjet printer, we have developed a low-cost, widely applicable way to make plasmonic materials,” Professor Nahata said. “Because we can draw and print these structures exactly as we want them, our technique lets you make rapid changes to the plasmonic properties of the metal, without the million-dollar instrumentation typically used to fabricate these structures.”

Professor Nahata and his colleagues used two different color cartridges filled with silver and carbon ink to print 10 different plasmonic structures with a periodic array of 2,500 holes with different sizes and spacing on a 2.5-inch-by-2.5 inch plastic sheet.

The four arrays tested had holes 450 microns in diameter – about four times the width of a human hair – and spaced one-25th of an inch apart. Depending on the relative amounts of silver and carbon ink used, the researchers couldMiesten keng?t laajasta valikoimasta