Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

A Guiding Light on the Nanoscale

03.09.2004


At left a zinc-oxide nanowire laser is pumped with light, which is channeled into a tin-oxide nanoribbon at a junction between the two materials and guided through the rest of the ribbon’s length. At right is an electron microscope image of the junction between wire and ribbon.


Another important step towards realizing the promise of lightning fast photonic technology has been taken by scientists with the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California at Berkeley. Researchers have demonstrated that semiconductor nanoribbons, single crystals measuring tens of hundreds of microns in length, but only a few hundred or less nanometers in width and thickness (about one ten-millionth of an inch), can serve as "waveguides" for channeling and directing the movement of light through circuitry.

"Not only have we shown that semiconductor nanoribbons can be used as low-loss and highly flexible optical waveguides, we’ve also shown that they have the potential to be integrated within other active optical components to make photonic circuits," says Peidong Yang, a chemist with Berkeley Lab’s Materials Sciences Division and a professor with UC Berkeley’s Chemistry Department, who led this research.

The research results of Yang and his team are reported in the August 27, 2004 issue of the journal Science. Co-authoring the paper along with Yang were Matt Law, Donald Sirbuly, Justin Johnson, Josh Goldberger and Richard Saykally, all of whom are with affiliated with Berkeley Lab, UC Berkeley, or both.



In photonic technology, or photonics, the use of electrons moving through semiconductors as information carriers is replaced with the movement of light waves, as measured in units of energy called photons. Whereas electrons must carry information sequentially, one electron at a time, with photons of light there’s virtually no limit to the number of information packets that can simultaneously be transmitted. Call it unparalleled parallel processing.

Hints of the potential of photonics can be glimpsed in today’s fiber-optic communications, where a single optical fiber can carry the equivalent of 300,000 telephone calls at the same time. But the power of fully realized photonics goes far beyond this. For example, it’s been estimated that a photonic internet could transmit data at 160 gigabits per second, which is thousands of times faster than today’s typical high-speed connection. Another possibility is the optical computer, which could solve problems in seconds that would take today’s electronic computers months or even years to solve.

For the promise of photonics to be delivered, however, scientists must first find a way to manipulate and route photons with the same dexterity as they manipulate and route electrons. Whereas other research efforts have successfully experimented with the use of photonic band-gap materials to accomplish this, Yang and his colleagues have focused on the chemical synthesis of nanowires and nanoribbons — they’re like nanotubes only solid throughout rather than hollow inside — that can then be assembled into photonic circuits.

"Chemically synthesized nanowires and nanoribbons have several features that make them good photonic building blocks," says Yang. "They offer inherent one-dimensionality, a diversity of optical and electrical properties, good size control, low surface roughness and, in principle, the ability to operate above and below light-diffraction limits."

Yang and his colleagues synthesized their nanoribbon waveguides from tin oxide, a semiconductor of keen technological interest for its exceptional potential for use in transporting both photons and electrons in nanoscale (also referred to as "subwavelength") components. The single crystalline nanoribbons they produced measured about 1,500 microns in length and featured a variety of widths and thicknesses. Yang says ribbons that measured between 100 to 400 nanometers in width and thickness proved to be ideal for guiding visible and ultraviolet light.

"To steer visible and ultraviolet light within dielectric waveguides, such as the tin oxide crystals we were synthesizing, we needed to make sure that a sufficient portion of the light’s electromagnetic field was confined within the nanostructures so there would be minimal optical transmission loss," Yang says. "Considering the dielectric constant of the tin oxide, it follows that the diameter of 100 to 400 nanometers would be ideal for waveguiding light that measures from 300 to 800 nanometers in wavelengths."

In their tests, Yang and his colleagues attached nanowire lasers and optical detectors to opposite ends of their tin oxide nanoribbons, then demonstrated that light could be propagated and modulated through subwavelength optical cavities within the nanoribbons. The nanoribbons were long and strong enough to be pushed, bent, and shaped with the use of a commercial micromanipulator under an optical microscope. Freestanding ribbons were also extremely flexible and could be curved through tight S-turns and twisted into a variety of shapes, which Yang says is "remarkable for a crystal that is brittle in its bulk form."

Yang also says that while the nanoribbon waveguides can be coupled together to create optical networks that could serve as the basis of miniaturized photonic circuitry, the ribbons need to be in close proximity, preferably in direct physical contact, to enable an efficient transfer of light between them. "We tested various coupling geometries and found that a staggered side-by-side arrangement, in which two ribbons interact over a distance of several micrometers, outperforms direct end-to-end coupling," Yang says.

The nanoribbon waveguides that Yang and his co-authors report in their Science paper are the newest addition to the growing assortment of nanosized device elements that Yang and his research group have been able to make. Their "toolbox" now includes nanoscale lasers and photodetectors, in addition to the nanoribbon waveguides.

"Ultimately, we would like to integrate all these individual components together into a photonic system-on-a-chip, so that many photonic operations, including light emission, routing, and detection, can be done on a much smaller scale," says Yang.

Lynn Yarris | EurekAlert!
Further information:
http://www.lbl.gov

More articles from Power and Electrical Engineering:

nachricht Producing electricity during flight
20.09.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau

nachricht Solar-to-fuel system recycles CO2 to make ethanol and ethylene
19.09.2017 | DOE/Lawrence Berkeley National Laboratory

All articles from Power and Electrical Engineering >>>

The most recent press releases about innovation >>>

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

Im Focus: The pyrenoid is a carbon-fixing liquid droplet

Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.

A warming planet

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

Im Focus: Quantum Sensors Decipher Magnetic Ordering in a New Semiconducting Material

For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.

Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Rainbow colors reveal cell history: Uncovering β-cell heterogeneity

22.09.2017 | Life Sciences

Penn first in world to treat patient with new radiation technology

22.09.2017 | Medical Engineering

Calculating quietness

22.09.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>