Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Penn Researchers Build First Physical “Metatronic” Circuit

24.02.2012
The technological world of the 21st century owes a tremendous amount to advances in electrical engineering, specifically, the ability to finely control the flow of electrical charges using increasingly small and complicated circuits. And while those electrical advances continue to race ahead, researchers at the University of Pennsylvania are pushing circuitry forward in a different way, by replacing electricity with light.

“Looking at the success of electronics over the last century, I have always wondered why we should be limited to electric current in making circuits,” said Nader Engheta, professor in the electrical and systems engineering department of Penn’s School of Engineering and Applied Science. “If we moved to shorter wavelengths in the electromagnetic spectrum — like light — we could make things smaller, faster and more efficient.”


Figure A. When the plane of the electric field is in line with the nanorods the circuit is wired in parallel.


Figure B. When the plane of the electric field crosses both the nanorods and the gaps the circuit is wired in series.

Different arrangements and combinations of electronic circuits have different functions, ranging from simple light switches to complex supercomputers. These circuits are in turn built of different arrangements of circuit elements, like resistors, inductors and capacitors, which manipulate the flow of electrons in a circuit in mathematically precise ways. And because both electric circuits and optics follow Maxwell’s equations — the fundamental formulas that describe the behavior of electromagnetic fields — Engheta’s dream of building circuits with light wasn’t just the stuff of imagination. In 2005, he and his students published a theoretical paper outlining how optical circuit elements could work.

Now, he and his group at Penn have made this dream a reality, creating the first physical demonstration of “lumped” optical circuit elements. This represents a milestone in a nascent field of science and engineering Engheta has dubbed “metatronics.”

Engheta’s research, which was conducted with members of his group in the electrical and systems engineering department, Yong Sun, Brian Edwards and Andrea Alù, was published in the journal Nature Materials.

In electronics, the “lumped” designation refers to elements that can be treated as a black box, something that turns a given input to a perfectly predictable output without an engineer having to worry about what exactly is going on inside the element every time he or she is designing a circuit.

“Optics has always had its own analogs of elements, things like lenses, waveguides and gratings,” Engheta said, “but they were never lumped. Those elements are all much larger than the wavelength of light because that’s all that could be easily built in the old days. For electronics, the lumped circuit elements were always much smaller than the wavelength of operation, which is in the radio or microwave frequency range.”

Nanotechnology has now opened that possibility for lumped optical circuit elements, allowing construction of structures that have dimensions measured in nanometers. In this experiment’s case, the structure was comb-like arrays of rectangular nanorods made of silicon nitrite.

The “meta” in “metatronics” refers to metamaterials, the relatively new field of research where nanoscale patterns and structures embedded in materials allow them to manipulate waves in ways that were previously impossible. Here, the cross-sections of the nanorods and the gaps between them form a pattern that replicates the function of resistors, inductors and capacitors, three of the most basic circuit elements, but in optical wavelengths.

“If we have the optical version of those lumped elements in our repertoire, we can actually make designs similar to what we do in electronics but now for operation with light,” Engheta said. “We can build a circuit with light.”

In their experiment, the researchers illuminated the nanorods with an optical signal, a wave of light in the mid-infrared range. They then used spectroscopy to measure the wave as it passed through the comb. Repeating the experiment using nanorods with nine different combinations of widths and heights, the researchers showed that the optical “current” and optical “voltage” were altered by the optical resistors, inductors and capacitors with parameters corresponding to those differences in size.

“A section of the nanorod acts as both an inductor and resistor, and the air gap acts as a capacitor,” Engheta said.

Beyond changing the dimensions and the material the nanorods are made of, the function of these optical circuits can be altered by changing the orientation of the light, giving metatronic circuits access to configurations that would be impossible in traditional electronics.

This is because a light wave has polarizations; the electric field that oscillates in the wave has a definable orientation in space. In metatronics, it is that electric field that interacts and is changed by elements, so changing the field’s orientation can be like rewiring an electric circuit.

When the plane of the field is in line with the nanorods, as in Figure A, the circuit is wired in parallel and the current passes through the elements simultaneously. When the plane of the electric field crosses both the nanorods and the gaps, as in Figure B, the circuit is wired in series and the current passes through the elements sequentially.

“The orientation gives us two different circuits, which is why we call this ‘stereo-circuitry,’” Engheta said. “We could even have the wave hit the rods obliquely and get something we don’t have in regular electronics: a circuit that’s neither in series or in parallel but a mixture of the two.”

This principle could be taken to an even higher level of complexity by building nanorod arrays in three dimensions. An optical signal hitting such a structure’s top would encounter a different circuit than a signal hitting its side. Building off their success with basic optical elements, Engheta and his group are laying the foundation for this kind of complex metatronics.

“Another reason for success in electronics has to do with its modularity,” he said. “We can make an infinite number of circuits depending on how we arrange different circuit elements, just like we can arrange the alphabet into different words, sentences and paragraphs.

“We’re now working on designs for more complicated optical elements,” Engheta said. “We’re on a quest to build these new letters one by one.”

This work was supported in part by the U.S. Air Force Office of Scientific Research.

Andrea Alù is now an assistant professor at the University of Texas at Austin.

Evan Lerner | EurekAlert!
Further information:
http://www.upenn.edu

More articles from Materials Sciences:

nachricht Epoxy compound gets a graphene bump
14.11.2018 | Rice University

nachricht Automated adhesive film placement and stringer integration for aircraft manufacture
14.11.2018 | Fraunhofer IFAM

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A Chip with Blood Vessels

Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.

Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...

Im Focus: A Leap Into Quantum Technology

Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.

In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...

Im Focus: Research icebreaker Polarstern begins the Antarctic season

What does it look like below the ice shelf of the calved massive iceberg A68?

On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.

Im Focus: Penn engineers develop ultrathin, ultralight 'nanocardboard'

When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure

Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...

Im Focus: Coping with errors in the quantum age

Physicists at ETH Zurich demonstrate how errors that occur during the manipulation of quantum system can be monitored and corrected on the fly

The field of quantum computation has seen tremendous progress in recent years. Bit by bit, quantum devices start to challenge conventional computers, at least...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

“3rd Conference on Laser Polishing – LaP 2018” Attracts International Experts and Users

09.11.2018 | Event News

On the brain’s ability to find the right direction

06.11.2018 | Event News

European Space Talks: Weltraumschrott – eine Gefahr für die Gesellschaft?

23.10.2018 | Event News

 
Latest News

Epoxy compound gets a graphene bump

14.11.2018 | Materials Sciences

Microgel powder fights infection and helps wounds heal

14.11.2018 | Health and Medicine

How algae and carbon fibers could sustainably reduce the athmospheric carbon dioxide concentration

14.11.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>