Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

’Nanoantennas’ could bring sensitive detectors, optical circuits

22.08.2002


Researchers have shown how tiny wires and metallic spheres might be arranged in various shapes to form "nanoantennas" that dramatically increase the precision of medical diagnostic imaging and devices that detect chemical and biological warfare agents.



Engineers from Purdue University have demonstrated through mathematical simulations that nanometer-scale antennas with certain geometric shapes should be able to make possible new sensors capable of detecting a single molecule of a chemical or biological agent. Such an innovation could result in detectors that are, in some cases, millions of times more sensitive than current technology.

The nanoantennas in the simulations are made of metal wires and spheres only about 10 nanometers thick – or roughly 100 atoms wide. They are an example of "left-handed" materials, meaning they are able to reverse the normal behavior of visible light and other forms of electromagnetic radiation.


Ordinary materials, such as glass, plastic, air and water, are called "right-handed" because of the way in which light bends as it penetrates a material. Left-handed materials have the ability to bend waves of electromagnetic radiation in the opposite direction of right-handed materials. This unusual property means that such materials might be used to create a so-called "super lens" that drastically improves the quality of medical diagnostic images.

The Purdue researchers are the first to show precisely how left-handed materials – the nanoantennas – could be applied to visible light and other electromagnetic radiation consisting of short wavelengths. Scientists at the University of California at San Diego proved two years ago that left-handed materials could be applied to devices that use microwaves, which are much longer than the waves needed for medical imaging, and for sensors used in spectroscopy to detect chemicals and biological agents. The phenomenon was first predicted in the late 1960s.

"All of the work in this area so far has been done in the microwave spectral range," said Vladimir Shalaev, a professor in Purdue’s School of Electrical and Computer Engineering. "We believe that this is the first project for how these types of materials can be used in the visible range of the electromagnetic spectrum."

The Purdue researchers have shown in theory how the same phenomenon could be scaled down to devices only nanometers wide. The research also shows how nanoantennas with specific shapes are critical for receiving certain frequencies of electromagnetic radiation. The findings were published in the March issue of the Journal of Nonlinear Optical Physics and Materials. The paper was written by Shalaev, Viktor A. Podolskiy, a post-doctoral fellow at Princeton University, and Andrey K. Sarychev, a senior research scientist at Purdue.

Purdue researchers plan to take the work a step further by creating the nanoantennas and conducting experiments to support the theoretical calculations, Shalaev said.

"Left-handed materials might have loads of applications," Shalaev said. "We don’t know yet the full potential of these materials because it’s a really new field."

The researchers showed how the nanoantennas could be created by arranging pairs of tiny wires parallel to each other. That arrangement, in theory, enables the nanoantennas to achieve a "negative index of refraction," said Shalaev, a physicist by training.

Light and other forms of radiation bend as they pass through a material. Physicists measure this bending of radiation by its "index of refraction." The larger a material’s index, the slower light travels through it, and the more it bends, or changes direction when going from one material to a different one. Because left-handed materials bend light in precisely the opposite direction as right-handed materials, they are said to have a "negative index of refraction."

"With these new types of materials, it may be possible to accomplish better performance than all existing materials, in terms of making images and manipulating light," Shalaev said.

The nanoantennas work by using clouds of electrons, all moving in unison as if they were a single object instead of millions of individual electrons. These groups of electrons are known collectively as "plasmons."

Researchers hope to one day use nanoantennas to create more compact, faster circuits and computers that use packets of light, called photons, instead of electrons for carrying signals. Photons travel much faster than electrons, but, unlike electrons, they do not possess an electrical charge. This lack of an electrical charge makes it far more difficult to manipulate photons.

"Because electrons are negatively charged particles, it’s easy to manipulate them," Shalaev said. "You just apply a field and they start moving.

"It turns out that, by employing these plasmonic nanomaterials, you should be able to manipulate light. You can guide light. You can basically simulate all the basic fundamental properties of electronic circuits, but in this case photons start to work."

Such photonic circuits could usher in a new class of ultrasensitive sensors that detect tiny traces of chemicals and biological materials, making them useful for applications including analyzing a patient’s DNA for medical diagnostics, monitoring air quality for pollution control and detecting dangerous substances for homeland security.

"This could be a way to dramatically enhance sensitivity in detecting molecules," Shalaev said. "That’s a great goal. These plasmonic nanomaterials accumulate electromagnetic energy in extremely small areas, nanoscale areas. It’s like focusing light in areas much smaller than the wavelengths of light.

"Conventional lenses cannot focus light in an area smaller than the wavelength of the light. When you use these plasmonic nanomaterials, which act like nanoantennas, you do focus light in areas much smaller than the wavelengths. This means that metallic nanostructures might be able to detect even a single molecule of a substance, which is not possible with conventional optics."

The nanoantenna shapes used in the simulations ranged from single spheres to more complex geometric configurations called "fractals," in which the same shape is repeated in smaller and smaller sections.

Using metallic structures only a few nanometers thick is critical to applying the technique to visible light.

"Light cannot go into metals," Shalaev said. "But when you take a very small piece of metal, the light goes through completely and you very efficiently excite the whole piece of metal."

The research has been funded by the National Science Foundation.

Writer: Emil Venere, (765) 494-4709, venere@purdue.edu
Source: Vladimir Shalaev, (765) 494-9855, shalaev@ecn.purdue.edu
Purdue News Service: (765) 494-2096; purduenews@purdue.edu
NOTE TO JOURNALISTS: An electronic or paper copy of the research paper is available from Emil Venere, (765) 494-4709, venere@purdue.edu.

Emil Venere | EurekAlert!
Further information:
http://www.purdue.edu/

More articles from Process Engineering:

nachricht Quick, Precise, but not Cold
17.05.2017 | Fraunhofer-Institut für Lasertechnik ILT

nachricht A laser for divers
03.05.2017 | Laser Zentrum Hannover e.V.

All articles from Process Engineering >>>

The most recent press releases about innovation >>>

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

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

Cholesterol-lowering drugs may fight infectious disease

22.08.2017 | Health and Medicine

Meter-sized single-crystal graphene growth becomes possible

22.08.2017 | Materials Sciences

Repairing damaged hearts with self-healing heart cells

22.08.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>