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Primeur weekly 2013-09-23

Exascale supercomputing

Supercomputers for all: The next frontier for Europe's high performance computing ...

The Cloud

DataDirect Networks ushers in a new era of scale, speed and data insight for web-scale and Big Data applications ...

Cybersecurity researcher joins the ranks of the 'brilliant' ...

IBM commits $1 billion to fuel Linux and open source innovation on Power systems ...

Siemens plans North American HR technology Cloud migration to Oracle Fusion HCM with help from KPMG ...

HP announces Cloud-driven enhancements to application and catabase archiving solution ...

EuroFlash

AMS-IX starts new regional Internet exchange hub in Mombasa, Kenya, in collaboration with KIXP ...

Altair announces most successful UK technology event to date ...

Graphene photodetector integrated into computer chip ...

PRACE pre-commercial procurement of whole system design for energy efficient HPC ...

Severo Ochoa (SO) programme at Barcelona Supercomputing Center ...

Quantum entanglement only dependent upon area ...

University of Leicester hosts national supercomputing meeting, showcasing science from the smallest and largest scales ...

USFlash

Six vendors complete test event to become part of OpenFabrics Alliance Interoperability Logo Programme ...

OpenFabrics Alliance announces formation of OpenFramework Working Group ...

DataDirect Networks and ASG partner to offer a private Cloud solution for high performance, high availability archive and collaboration ...

DataDirect Networks to power business-critical broadcast system servicing for Starz ...

Connecting the future ...

$50 million NSF grant to advance cyberinfrastructure for Big Data in life sciences ...

Supercomputing the transition from ordinary to extraordinary forms of matter ...

Cray adds large memory and shared memory solutions to its line of Cray CS300 cluster supercomputers ...

On the road to fault-tolerant quantum computing ...

Bold idea for 'Big Data' ...

NASA uses supercomputer to create future climate projections for the United States ...

Supercomputer sheds weight, gains mobility, and becomes "Server-on-the-Go" ...

Graphene could yield cheaper optical chips ...

Scaling up personalized query results for next generation of search engines ...

Graphene could yield cheaper optical chips


15 Sep 2013 Cambridge - Graphene, which consists of atom-thick sheets of carbon atoms arranged hexagonally, is the new wonder material: Flexible, lightweight and incredibly conductive electrically, it's also the strongest material known to man.

In the latest issue ofNature Photonics, researchers at MIT, Columbia University and IBM's T. J. Watson Research Center describe a promising new application of graphene, in the photodetectors that would convert optical signals to electrical signals in integrated opto-electronic computer chips. Using light rather than electricity to move data both within and between computer chips could drastically reduce their power consumption and heat production, problems that loom ever larger as chips’ computational capacity increases.

Opto-electronic devices built from graphene could be much simpler in design than those made from other materials. If a method for efficiently depositing layers of graphene - a major area of research in materials science - can be found, it could ultimately lead to optoelectronic chips that are simpler and cheaper to manufacture.

"Another advantage, besides the possibility of making device fabrication simpler, is that the high mobility and ultrahigh carrier-saturation velocity of electrons in graphene makes for very fast detectors and modulators", stated Dirk Englund, the Jamieson Career Development Assistant Professor of Electrical Engineering and Computer Science at MIT, who led the new research.

Graphene is also responsive to a wider range of light frequencies than the materials typically used in photodetectors, so graphene-based opto-electronic chips could conceivably use a broader-band optical signal, enabling them to move data more efficiently. "A two-micron photon just flies straight through a germanium photodetector", Dirk Englund stated, "but it is absorbed and leads to measurable current - as we actually show in the paper - in graphene."

As Dirk Englund explained, the problem with graphene as a photodetector has traditionally been its low responsivity: A sheet of graphene will convert only about 2 percent of the light passing through it into an electrical current. That's actually quite high for a material only an atom thick, but it’s still too low to be useful.

When light strikes a photo-electric material like germanium or graphene, it kicks electrons orbiting atoms of the material into a higher energy state, where they're free to flow in an electrical current. If they don't immediately begin to move, however, they'll usually drop back down into the lower energy state. So one standard trick for increasing a photodetector's responsivity is to "bias" it - to apply a voltage across it that causes the electrons to flow before they lose energy.

The problem is that the voltage will inevitably induce a slight background current that adds "noise" to the detector's readings, making them less reliable. So Dirk Englund, his student Ren-Jye Shiue, Columbia's Xuetao Gan - who, together with Ren-Jye Shiue, is lead author on the paper - and their collaborators instead used a photodetector design developed by Fengnian Xia and his colleagues at IBM, which produces a slight bias without the application of a voltage.

In the new design, light enters the detector through a silicon channel - a "waveguide" - etched into the surface of a chip. The layer of graphene is deposited on top of and perpendicular to the waveguide. On either side of the graphene layer is a gold electrode. But the electrodes' placement is asymmetrical: One of them is closer to the waveguide than the other.

"There's a mismatch between the energy of electrons in the metal contact and in graphene", Dirk Englund stated, "and this creates an electric field near the electrode." When electrons are kicked up by photons in the waveguide, the electric field pulls them to the electrode, creating a current.

In experiments, the researchers found that, unbiased, their detector would generate 16 milliamps of current for each watt of incoming light. Its detection frequency was 20 gigahertz - already competitive with germanium. Some experimental germanium photodetectors have achieved higher speeds, but only when biased. With the application of a slight bias, the detector could get up to 100 milliamps per watt, a responsivity commensurate with that of germanium.

Dirk Englund is confident that better engineering - thinner electrodes, or a narrower waveguide - could yield a photodetector whose responsivity is even higher. "It's a matter of engineering", he stated. "We are already testing some new tricks to get another factor of two or four."

"I think it's great work", stated Thomas Mueller, an assistant professor at the Vienna University of Technology's Photonics Institute. "The main drawback of graphene photodetectors was always their low responsivity. Now they have two orders of magnitude higher responsivity, which is really great."

"The other thing that I like very much is the integration with a silicon chip", Thomas Mueller added, "which really shows that, in the end, you’ll be able to integrate graphene into computer chips to realize optical links and things like that."

In fact, the same issue ofNature Photonicsalso features a paper by Thomas Mueller and colleagues, reporting work very similar to that conducted by Dirk Englund and his team. "We did not know that we were doing the same thing", Thomas Mueller stated. "But I'm very happy that two papers are coming out in the same journal on the same topic, which shows that it's an important thing, I think."

The chief difference between the two groups' work, Thomas Mueller said, is that "we used slightly different geometry." But, he added: "Honestly, I think that Dirk's geometry is more practical. We were also thinking about the same thing, but we didn't have the technical capabilities to do this. There's one process that they do that we were not able to do."
Source: Massachusetts Institute of Technology - MIT

Back to Table of contents

Primeur weekly 2013-09-23

Exascale supercomputing

Supercomputers for all: The next frontier for Europe's high performance computing ...

The Cloud

DataDirect Networks ushers in a new era of scale, speed and data insight for web-scale and Big Data applications ...

Cybersecurity researcher joins the ranks of the 'brilliant' ...

IBM commits $1 billion to fuel Linux and open source innovation on Power systems ...

Siemens plans North American HR technology Cloud migration to Oracle Fusion HCM with help from KPMG ...

HP announces Cloud-driven enhancements to application and catabase archiving solution ...

EuroFlash

AMS-IX starts new regional Internet exchange hub in Mombasa, Kenya, in collaboration with KIXP ...

Altair announces most successful UK technology event to date ...

Graphene photodetector integrated into computer chip ...

PRACE pre-commercial procurement of whole system design for energy efficient HPC ...

Severo Ochoa (SO) programme at Barcelona Supercomputing Center ...

Quantum entanglement only dependent upon area ...

University of Leicester hosts national supercomputing meeting, showcasing science from the smallest and largest scales ...

USFlash

Six vendors complete test event to become part of OpenFabrics Alliance Interoperability Logo Programme ...

OpenFabrics Alliance announces formation of OpenFramework Working Group ...

DataDirect Networks and ASG partner to offer a private Cloud solution for high performance, high availability archive and collaboration ...

DataDirect Networks to power business-critical broadcast system servicing for Starz ...

Connecting the future ...

$50 million NSF grant to advance cyberinfrastructure for Big Data in life sciences ...

Supercomputing the transition from ordinary to extraordinary forms of matter ...

Cray adds large memory and shared memory solutions to its line of Cray CS300 cluster supercomputers ...

On the road to fault-tolerant quantum computing ...

Bold idea for 'Big Data' ...

NASA uses supercomputer to create future climate projections for the United States ...

Supercomputer sheds weight, gains mobility, and becomes "Server-on-the-Go" ...

Graphene could yield cheaper optical chips ...

Scaling up personalized query results for next generation of search engines ...