The ability to stream videos online with the quality of high-end home theater
systems, and to run computer programs a thousand times faster, are some of the
future advances being made possible by a Penn
State research team led by Tony Jun Huang, the James Henderson assistant
professor of engineering science and mechanics.
Huang's Biofunctionalized NanoElectroMechanicalSystems (BioNEMS) group has
developed a working plasmonic switch, the first step in building optical computers
with frequencies 100,000 times greater than the ones of current microprocessors.
Huang explained, "Computer chips have circuits. Today's electronic circuits
are good and small, but they're slow and have low capacity, relatively speaking.
To make the big jump, we need to develop photonic circuits. Photonic circuits
use light to carry information, similar to the technology behind fiber optic
cables, and have higher speeds and higher capacities. But the problem with photonic
circuits is that they're too big."
The answer, Huang said, is to create something that combines the speed and
capacity of photonic circuits with the small size of electronic circuits —
a plasmonic circuit.
''Plasmonic circuits are a hybrid of electronics and photonics,'' he stated.
''They can transmit electrons and light at the same time.''
Huang's BioNEMS group has been focusing on the first step towards a plasmonic
circuit puzzle: the plasmonic switch.
''In electronic circuits, transistors amplify and switch electric current to
realize two different states: ones and zeros,'' he said. ''It's the same for
plasmonic circuits where plasmonic transistors and switches are required.''
The plasmonic switches designed so far haven't been very efficient, the engineer
stated. ''Few people have made plasmonic switches. They have used chemicals
or electricity to do the switching. Using chemicals is very slow and would produce
waste because you have two chemicals that have to react. It's just not practical.
"Using electricity is better, but we want to make our whole system modulated
by light. So using electricity to drive it is not as compatible as a light-driven
device as we're proposing.''
Huang's team, which includes postdoctoral researcher Vincent Hsiao and graduate
students Yuebing Zheng and Bala Krishna Juluri, has done just that, creating
a light-driven plasmonic switch. Molecules in the group's plasmonic switch change
shape, causing the device's liquid crystals to align or de-align, in essence
changing from a one to a zero.
The work has already caused a stir in the scientific community. It has been
featured as the cover image of the Sep. 17, 2008, issue of the journal Advanced
Materials. It also was recently highlighted in the journal Nature Photonics.
''There's still a long way to go,'' cautioned Huang. He characterizes the team's
work as more fundamental research instead of applied work. ''There are a lot
of questions we have not been able to answer at this moment.''
The BioNEMS team will continue its work in plasmonic switches, including investigating
different nanomaterials that might work better.
Huang thinks that it may be at least five years before a true working plasmonic
circuit might be created.
''Practically, we have to be able to integrate these plasmonic switches with
other components, such as plasmonic waveguides, before we can demonstrate a
plansmonic circuit.''
Posted January 16th, 2009
