Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Groundbreaking optical device could enhance optical information processing, computers

07.04.2014

At St. Paul's Cathedral in London, a section of the dome called the Whispering Gallery makes a whisper audible from the other side of the dome as a result of the way sound waves travel around the curved surface.

Researchers at Washington University in St. Louis have used the same phenomenon to build an optical device that may lead to new and more powerful computers that run faster and cooler.


This is a diagram of the optical diode developed by Lan Yang, Ph.D., associate professor of electrical systems engineering, and her collaborators.

Credit: Lan Yang

Lan Yang, PhD, associate professor of electrical and systems engineering, and her collaborators have developed an essential component of these new computers that would run on light. Their work brings predictions from recently formulated theoretical physics into real world applications.

The results of their research appear April 6 in Nature Physics.

Yang's group has created an optical diode by coupling tiny doughnut shaped optical resonators — one with gain and the other with loss — on a silicon chip. "This diode is capable of completely eliminating light transmission in one direction and greatly enhancing light transmission in the other nonreciprocal light transmission," says Bo Peng, a graduate student in Yang's group and the paper's lead author.

An electrical diode prevents electricity from backflow along a wire providing protection to crucial parts of an electronic circuit or processor; an optical diode does the same thing with light.

"We believe that our discovery will benefit many other fields involving electronics, acoustics, plasmonics and meta-materials," Yang says. "Coupling of so-called loss and gain devices using PT (parity-time)-symmetry could enable such advances as cloaking devices, stronger lasers that need less input power, and perhaps detectors that could 'see' a single atom."

The principle of PT-symmetry is based upon mathematical theories advanced by Carl M. Bender, PhD, the Wilfred R. and Ann Lee Konneker Distinguished Professor of Physics in Arts & Sciences at Washington University.

Simply put, when a "lossy" system is coupled with a "gain" system such that loss of energy exactly equals gain at an equilibrium point, a "phase transition" occurs.

Applying the principles of PT symmetry leads optics to a completely different set of behaviors not predicted by conventional physics with only loss or only gain. The phenomena that occur at the "phase transition" are dramatic and hitherto unexpected, Yang says.

To make their optical diode, Sahin Kaya Ozdemir, PhD, a research scientist in Yang's group and a key contributor to the paper, and Peng used two micro-resonators positioned so that light can flow from one to the other. One device is the "lossy" silica resonator.

The other incorporates the chemical element erbium into the silica structure for gain. Ozdemir says when erbium interacts with light of wavelength 1450 nm, it emits photons in the wavelength 1550 nm. A transmission detector set for 1550 nm will see a gain from this erbium-containing resonator.

When the rate of gain in one resonator exactly equals that of loss in the other, the phase transition occurs at a critical coupling distance between the resonators.

Most significantly, PT symmetry is broken, and the system shows a strong nonlinear behavior even at very weak input powers- input light gains intensity with a very steep non-linear slope. "As a result, time reversal symmetry is broken and light is able to move in only one direction— forward" says Yang.

"Time reversal symmetry is a fundamental physical rule that states that if light can travel in one direction, it must be able to travel in the opposite direction too. With this new optical diode, this is no longer the case," says Ozdemir. "Engineers traditionally use magneto-optics and high magnetic fields to break time reversal symmetry, here we do this using strong nonlinearity enabled by broken PT symmetry. With an input of only 1 microwatt, we show 17-fold enhancement of light transmission in one direction. There is no transmission in the other direction. Such a performance would not be possible without the use of resonant structures and PT-symmetric concepts."

"Our resonators are small enough to use in computers and future optical information processors. At present, we built our optical diodes from silica, which has very little material loss at the telecommunication wavelength. The concept can be extended to resonators made from other materials to enable easy CMOS compatibility." Peng says.

"More broadly, our paper shows how a concept with its roots in mathematical physics can be utilized to provide solutions to practical problems, opening new possibilities for controlling and manipulating light on-chip," the team says. "PT-symmetry breaking alone is not sufficient to have nonreciprocal response; operation in the nonlinear regime is also necessary. In the linear regime, light transmission is always reciprocal regardless of whether PT-symmetry is broken or not," cautions the team.

Yang and Ozdemir believe that the PT concept can be extended to electronics, acoustics and other fields to create one-way channels, and photonic devices with advanced functionalities, and they are already working on new experiments relying on PT-symmetry.

###

Peng B, Ozdemir S, Lei F, Monifi F, Gianfreda M, Long G, Fan S, Nori F, Bender C, Yang L. Parity-time-symmetric whispering gallery microcavities. Nature Physics, April 6, 2014, advance online publication. DOI: 10.1038/NPHYS2927.

Funding for this research was provided by the Army Research Office and the U.S. Department of Energy.

The School of Engineering & Applied Science at Washington University in St. Louis focuses intellectual efforts through a new convergence paradigm and builds on strengths, particularly as applied to medicine and health, energy and environment, entrepreneurship and security. With 82 tenured/tenure-track and 40 additional full-time faculty, 1,300 undergraduate students, 700 graduate students and more than 23,000 alumni, we are working to leverage our partnerships with academic and industry partners — across disciplines and across the world — to contribute to solving the greatest global challenges of the 21st century.

Neil Schoenherr | EurekAlert!
Further information:
http://www.wustl.edu

Further reports about: CMOS Groundbreaking physics processing transition wavelength

More articles from Physics and Astronomy:

nachricht Further Improvement of Qubit Lifetime for Quantum Computers
09.12.2016 | Forschungszentrum Jülich

nachricht Electron highway inside crystal
09.12.2016 | Julius-Maximilians-Universität Würzburg

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

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

Im Focus: Electron highway inside crystal

Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.

Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Researchers identify potentially druggable mutant p53 proteins that promote cancer growth

09.12.2016 | Life Sciences

Scientists produce a new roadmap for guiding development & conservation in the Amazon

09.12.2016 | Ecology, The Environment and Conservation

Satellites, airport visibility readings shed light on troops' exposure to air pollution

09.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>