Nanotechnology Now







Heifer International

Wikipedia Affiliate Button


DHgate

Home > Press > Applied physicists create building blocks for a new class of optical circuits

Schematics of two types of optical circuits: the three particle trimer functions as a nanoscale magnet, while the seven particle heptamer exhibits almost no scattering for a narrow range of wavelengths due to interference. Credit: The laboratory of Federico Cappaso, Harvard School of Engineering and Applied Sciences
Schematics of two types of optical circuits: the three particle trimer functions as a nanoscale magnet, while the seven particle heptamer exhibits almost no scattering for a narrow range of wavelengths due to interference. Credit: The laboratory of Federico Cappaso, Harvard School of Engineering and Applied Sciences

Abstract:
Scalable devices inspired by nature exhibit customizable optical properties suitable for applications ranging from highly sensitive sensors and detectors to invisibility cloaks

Applied physicists create building blocks for a new class of optical circuits

Cambridge, MA | Posted on June 2nd, 2010

Imagine creating novel devices with amazing and exotic optical properties not found in nature—by simply evaporating a droplet of particles on a surface.

By chemically building clusters of nanospheres from a liquid, a team of Harvard researchers, in collaboration with scientists at Rice University, the University of Texas at Austin, and the University of Houston, has developed just that.

The finding, published in the May 28 issue of Science, demonstrates simple scalable devices that exhibit customizable optical properties suitable for applications ranging from highly sensitive sensors and detectors to invisibility cloaks. Using particles consisting of concentric metallic and insulating shells, Jonathan Fan, a graduate student at the Harvard School of Engineering and Applied Sciences (SEAS), his lead co-author Federico Capasso, Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering at SEAS, and Vinothan Manoharan, Associate professor of Chemical Engineering and Physics at SEAS and Harvard's Physics Department, devised a bottom-up, self-assembly approach to meet the design challenge.

"A longstanding challenge in optical engineering has been to find ways to make structures of size much smaller than the wavelength that exhibit desired and interesting properties," says Fan. "At visible frequencies, these structures must be nanoscale."

In contrast, most nanoscale devices are fabricated using top-down approaches, akin to how computer chips are manufactured. The smallest sizes that can be realized by such techniques are severely constrained by the intrinsic limits of the fabrication process, such as the wavelength of light used in the process. Moreover, such methods are restricted to planar geometries, are expensive, and require intense infrastructure such as cleanrooms.

"With our bottom-up approach, we mimic the way nature creates innovative structures, which exhibit extremely useful properties," explains Capasso. "Our nanoclusters behave as tiny optical circuits and could be the basis of new technology such as detectors of single molecules, efficient and biologically compatible probes in cancer therapeutics, and optical tweezers to manipulate and sort out nano-sized particles. Moreover, the fabrication process is much simpler and cheaper to carry out."

The researcher's self-assembly method requires nothing more than a bit of mixing and drying. To form the clusters, the particles are first coated with a polymer, and a droplet of them is then evaporated on a water-repellent surface. In the process of evaporation, the particles pack together into small clusters. Using polymer spacers to separate the nanoparticles, the researchers were able to controllably achieve a two nanometer gap between the particles—far better resolution than traditional top-down methods allow.

Two types of resulting optical circuits are of considerable interest. A trimer, comprising three equally-spaced particles, can support a magnetic response, an essential property of invisibility cloaks and materials that exhibit negative refractive index.

"In essence, the trimer acts as a nanoscale resonator that can support a circulating loop of current at visible and near-infrared frequencies," says Fan. "This structure functions as a nanoscale magnet at optical frequencies, something that natural materials cannot do."

Heptamers, or packed seven particle structures, exhibit almost no scattering for a narrow range of well-defined colors or wavelengths when illuminated with white light. These sharp dips, known as Fano resonances, arise from the interference of two modes of electron oscillations, a "bright" mode and a non-optically active "dark" mode, in the nanoparticle.

"Heptamers are very efficient at creating extremely intense electric fields localized in nanometer-size regions where molecules and nanoscale particles can be trapped, manipulated, and detected. Molecular sensing would rely on detecting shifts in the narrow spectra dips," says Capasso.

Ultimately, all of the self-assembled circuit designs can be readily tuned by varying the geometry, how the particles are separated, and the chemical environment. In short, the new method allows a "tool kit" for manipulating "artificial molecules" in such a way to create optical properties at will, a feature the researchers expect is broadly generalizable to a host of other characteristics.

Looking ahead, the researchers plan to work on achieving higher cluster yields and hope to assemble three-dimensional structures at the macroscale, a "holy grail" of materials science.

"We are excited by the potentially scalability of the method," says Manoharan. "Spheres are the easiest shapes to assemble as they can be readily packed together. While we only demonstrated here planar particle clusters, our method can be extended to three-dimensional structures, something that a top-down approach would have difficulty doing."

Fan, Capasso, and Manoharan's co-authors included Chihhui Wu and Gennady Shvets of University of Texas at Austin; Jiming Bao of the University of Houston; and Kui Bao, Rizia Bardhan, Naomi Halas, and Peter Norlander, all of Rice University.

The researchers acknowledge the support of National Science Foundation, the Air Force Office of Scientific Research; the U.S. Department of Defense; the Robert A. Welch Foundation; and the Center for Advanced Solar Photophysics, a U.S. Department of Energy Frontier Research Center. The work was carried out at the Center for Nanoscale Systems at Harvard, a member of the National Nanotechnology Infrastructure Network.

####

For more information, please click here

Contacts:
Michael Patrick Rutter

617-496-3815

Copyright © Harvard 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

SEFCU, SUNY Poly CNSE Announce Winning Student-Led Teams in the 6th Annual $500,000 New York Business Plan Competition April 25th, 2015

Northwestern scientists develop first liquid nanolaser: Technology could lead to new way of doing 'lab on a chip' medical diagnostics April 25th, 2015

Nanotech-enabled moisturizer speeds healing of diabetic skin wounds: Spherical nucleic acids silence gene that interferes with wound healing April 24th, 2015

Fast and accurate 3-D imaging technique to track optically trapped particles April 24th, 2015

Govt.-Legislation/Regulation/Funding/Policy

SEFCU, SUNY Poly CNSE Announce Winning Student-Led Teams in the 6th Annual $500,000 New York Business Plan Competition April 25th, 2015

Northwestern scientists develop first liquid nanolaser: Technology could lead to new way of doing 'lab on a chip' medical diagnostics April 25th, 2015

ORNL reports method that takes quantum sensing to new level April 23rd, 2015

Electron spin brings order to high entropy alloys April 23rd, 2015

Possible Futures

Printing Silicon on Paper, with Lasers April 21st, 2015

A glass fiber that brings light to a standstill: By coupling photons to atoms, light in a glass fiber can be slowed down to the speed of an express train; for a short while it can even be brought to a complete stop April 9th, 2015

Nanotechnology in Medical Devices Market is expected to reach $8.5 Billion by 2019 March 25th, 2015

Nanotechnology Enabled Drug Delivery to Influence Future Diagnosis and Treatments of Diseases March 21st, 2015

Academic/Education

SEFCU, SUNY Poly CNSE Announce Winning Student-Led Teams in the 6th Annual $500,000 New York Business Plan Competition April 25th, 2015

Iranian Female Professor Awarded UNESCO Medal in Nanoscience April 20th, 2015

JPK reports on the use of the NanoWizard® 3 AFM system at the Hebrew University of Jerusalem April 14th, 2015

UK National Graphene Institute Selects Bruker as Official Partner: World-Leading Graphene Research Facility Purchases Multiple Bruker AFMs April 7th, 2015

Self Assembly

Scientists Use Nanoscale Building Blocks and DNA 'Glue' to Shape 3D Superlattices: New approach to designing ordered composite materials for possible energy applications April 23rd, 2015

Advances in molecular electronics: Lights on -- molecule on: Researchers from Dresden and Konstanz succeed in light-controlled molecule switching April 20th, 2015

Carnegie Mellon chemists create tiny gold nanoparticles that reflect nature's patterns April 9th, 2015

DWI scientists program the lifetime of self-assembled nanostructures April 9th, 2015

Nanomedicine

Northwestern scientists develop first liquid nanolaser: Technology could lead to new way of doing 'lab on a chip' medical diagnostics April 25th, 2015

Nanotech-enabled moisturizer speeds healing of diabetic skin wounds: Spherical nucleic acids silence gene that interferes with wound healing April 24th, 2015

Fast and accurate 3-D imaging technique to track optically trapped particles April 24th, 2015

A silver lining: UCSB researchers cradle silver nanoclusters inside synthetic DNA to create a programmed, tunable fluorescent array April 23rd, 2015

Sensors

ORNL reports method that takes quantum sensing to new level April 23rd, 2015

New class of 3D-printed aerogels improve energy storage April 22nd, 2015

‘Oxford Instruments Young Nanoscientist India Award 2015’ to Prof. Arindam Ghosh April 20th, 2015

Optical resonance-based biosensors designed for medical applications April 18th, 2015

Announcements

SEFCU, SUNY Poly CNSE Announce Winning Student-Led Teams in the 6th Annual $500,000 New York Business Plan Competition April 25th, 2015

Northwestern scientists develop first liquid nanolaser: Technology could lead to new way of doing 'lab on a chip' medical diagnostics April 25th, 2015

Nanotech-enabled moisturizer speeds healing of diabetic skin wounds: Spherical nucleic acids silence gene that interferes with wound healing April 24th, 2015

Fast and accurate 3-D imaging technique to track optically trapped particles April 24th, 2015

Tools

Fast and accurate 3-D imaging technique to track optically trapped particles April 24th, 2015

ORNL reports method that takes quantum sensing to new level April 23rd, 2015

Quantum 'paparazzi' film photons in the act of pairing up April 22nd, 2015

Richards-Kortum elected to American Academy of Arts and Sciences: April 22nd, 2015

Photonics/Optics/Lasers

Northwestern scientists develop first liquid nanolaser: Technology could lead to new way of doing 'lab on a chip' medical diagnostics April 25th, 2015

Fast and accurate 3-D imaging technique to track optically trapped particles April 24th, 2015

ORNL reports method that takes quantum sensing to new level April 23rd, 2015

Quantum 'paparazzi' film photons in the act of pairing up April 22nd, 2015

Research partnerships

Pseudoparticles travel through photoactive material: KIT scientists measure important process in the conversion of light energy -- publication in Nature Communications April 24th, 2015

Electron spin brings order to high entropy alloys April 23rd, 2015

Surface matters: Huge reduction of heat conduction observed in flat silicon channels April 23rd, 2015

Drexel materials scientists putting a new spin on computing memory April 22nd, 2015

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