Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

Home > Press > Nano antenna concentrates light

A colorized scanning electron microscope image of gold tips in a nanogap device used in experiments to capture and amplify light. (Image courtesy Natelson Lab/Rice University)
A colorized scanning electron microscope image of gold tips in a nanogap device used in experiments to capture and amplify light. (Image courtesy Natelson Lab/Rice University)

Abstract:
Intensity increases 1,000-fold in Rice lab's experiment

Nano antenna concentrates light

Houston, TX | Posted on September 20th, 2010

Everybody who's ever used a TV, radio or cell phone knows what an antenna does: It captures the aerial signals that make those devices practical. A lab at Rice University has built an antenna that captures light in the same way, at a small scale that has big potential.

Condensed matter physicist Doug Natelson and graduate student Dan Ward have found a way to make an optical antenna from two gold tips separated by a nanoscale gap that gathers light from a laser. The tips "grab the light and concentrate it down into a tiny space," Natelson said, leading to a thousand-fold increase in light intensity in the gap.

Getting an accurate measurement of the effect is a first, said Natelson, who reported the results in today's online edition of the journal Nature Nanotechnology. He expects the discovery will be useful in the development of tools for optics and for chemical and biological sensing, even at the single-molecule scale, with implications for industrial safety, defense and homeland security.

The paper by Natelson, Ward and their colleagues in Germany and Spain details the team's technique, which involves shining laser light into the gap between a pair of gold tips less than a nanometer apart - about a hundred-thousandth the width of a human hair.

"You can ignore the fact that your car antenna is built out of atoms; it just works," said Natelson, a Rice professor of physics and astronomy, and also electrical and computer engineering. "But when you have tiny pieces of metal very close to each other, you have to worry about all the details. The fields are going to be big, the situation's going to be complicated and you're really constrained. We've been able to use some physics that only come into play when things are very close together to help figure out what's going on."

The key to measuring light amplification turned out to be measuring something else, specifically the electrical current flowing between the gold tips.

Putting the nanotips so close together allows charge to flow via quantum tunneling as the electrons are pushed from one side to the other. The researchers could get electrons moving by pushing them at low frequencies with a voltage, in a highly controllable, measurable way. They could also get them flowing by shining the laser, which pushes the charge at the very high frequency of the light. Being able to compare the two processes set a standard by which the light amplification could be determined, Natelson said. Their German and Spanish coauthors helped supply the necessary theoretical justification for the analysis.

The amplification is a plasmonic effect, Natelson said. Plasmons, which may be excited by light, are oscillating electrons in metallic structures that act like ripples in a pool. "You've got a metal structure, you shine light on it, the light makes the electrons in this metal structure slosh around," he said. "You can think of the electrons in the metal as an incompressible fluid, like water in a bathtub. And when you get them sloshing back and forth, you get electric fields.

"At the surfaces of the metal, these fields can be very big - much bigger than those from the original radiation," he said. "What was hard to measure was just how big. We didn't know how much the two sides were sloshing up and down - and that's exactly the thing we care about."

By simultaneously measuring the low-frequency electrically driven and the high-frequency optically driven currents between the tips, "we can figure out the voltage zinging back and forth at the really high frequencies that are characteristic of light," he said.

Natelson said his lab's homebuilt apparatus, which combines nanoscale electronics and optics, is fairly unusual. "There are a lot of people who do optics. There are a lot who do nanoscale electrical measurements," he said. "There are still not too many people who combine the two."

The custom rig gave the Rice researchers a measure of control over thermal and electrical properties that have stymied other investigators. The tips are cooled to 80 Kelvin, about -315 degrees Fahrenheit, and are electrically insulated from their silicon bases, keeping at bay stray voltages that could skew the results.

"The reason we're studying these enhanced fields is not just because they're there," Natelson said. "If you can enhance the local field by a factor of 1,000, there are lots of things you can do in terms of sensors and non-linear optics. Anything that gives you a handle on what's happening at these tiny scales is very useful.

"This is one of those rare, happy cases where you are able to actually get information - very local information - about exactly something you care about."

The paper's co-authors are Falco Hüser and Fabian Pauly of the Karlsruhe Institute of Technology, Germany; and Juan Carlos Cuevas at the Autonomous University of Madrid, Spain.

Support for the project came from the Robert A. Welch Foundation, the Lockheed Martin Advanced Nanotechnology Center of Excellence at Rice (LANCER), Deutsche Forschungsgemeinschaft, the Baden-Württemberg Siftung, the European Union through the Bio-Inspired Approaches for Molecular Electronics (BIMORE) network, and the Spanish Ministry of Science and Innovation.

Read the abstract at www.nature.com/nnano/journal/vaop/ncurrent/abs/nnano.2010.176.html

####

About Rice University
Located in Houston, Rice University is consistently ranked one of America's best teaching and research universities. Known for its "unconventional wisdom," Rice is distinguished by its: size -- 3,102 undergraduates and 2,237 graduate students; selectivity -- 12 applicants for each place in the freshman class; resources -- an undergraduate student-to-faculty ratio of 5-to-1; sixth largest endowment per student among American private research universities; residential college system, which builds communities that are both close-knit and diverse; and collaborative culture, which crosses disciplines, integrates teaching and research, and intermingles undergraduate and graduate work.

For more information, please click here

Contacts:
Mike Williams
Senior Media Relations Specialist
Office of Public Affairs/News & Media Relations
Rice University
(office) 713-348-6728
(cell) 617-281-6854


Jessica Stark
Rice University
Assistant Director
News and Media Relations
(office) 713-348-6777
(mobile) 513-309-5843

Copyright © Rice University

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

Seeing the quantum future... literally: What if big data could help you see the future and prevent your mobile phone from breaking before it happened? January 16th, 2017

NUS researchers achieve major breakthrough in flexible electronics: New classes of printable electrically conducting polymer materials make better electrodes for plastic electronics and advanced semiconductor devices January 14th, 2017

Manchester scientists tie the tightest knot ever achieved January 13th, 2017

Nanoscale Modifications can be used to Engineer Electrical Contacts for Nanodevices January 13th, 2017

Govt.-Legislation/Regulation/Funding/Policy

Chemistry on the edge: Experiments at Berkeley Lab confirm that structural defects at the periphery are key in catalyst function January 13th, 2017

Recreating conditions inside stars with compact lasers: Scientists offer a new path to creating the extreme conditions found in stars, using ultra-short laser pulses irradiating nanowires January 12th, 2017

Deciphering the beetle exoskeleton with nanomechanics: Understanding exoskeletons could lead to new, improved artificial materials January 12th, 2017

New laser based on unusual physics phenomenon could improve telecommunications, computing January 12th, 2017

Academic/Education

Oxford Nanoimaging report on how the Nanoimager, a desktop microscope delivering single molecule, super-resolution performance, is being applied at the MRC Centre for Molecular Bacteriology & Infection November 22nd, 2016

The University of Applied Sciences in Upper Austria uses Deben tensile stages as an integral part of their computed tomography research and testing facility October 18th, 2016

Enterprise In Space Partners with Sketchfab and 3D Hubs for NewSpace Education October 13th, 2016

New Agricultural Research Center Debuts at UCF October 12th, 2016

Announcements

Seeing the quantum future... literally: What if big data could help you see the future and prevent your mobile phone from breaking before it happened? January 16th, 2017

NUS researchers achieve major breakthrough in flexible electronics: New classes of printable electrically conducting polymer materials make better electrodes for plastic electronics and advanced semiconductor devices January 14th, 2017

Manchester scientists tie the tightest knot ever achieved January 13th, 2017

Nanoscale Modifications can be used to Engineer Electrical Contacts for Nanodevices January 13th, 2017

Tools

Distinguishing truth under the surface: electrostatic or mechanic December 31st, 2016

Nanomechanics Inc. Continues Growth in Revenue and Market Penetration: Leading nanoindentation company reports continued growth in revenues and distribution channels on national and international scales December 27th, 2016

Nanometrics to Present at the 19th Annual Needham Growth Conference December 22nd, 2016

Safe and inexpensive hydrogen production as a future energy source: Osaka University researchers develop efficient 'green' hydrogen production system that operates at room temperature in air December 21st, 2016

NanoNews-Digest
The latest news from around the world, FREE




  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project