Nanotechnology Now

Our NanoNews Digest Sponsors


Heifer International

Wikipedia Affiliate Button


DHgate

Home > Press > Penn Researchers Break Light-Matter Coupling Strength Limit in Nanoscale Semiconductors

A computer simulation of a one-dimensional cavity wave in a 200nm nanowire
A computer simulation of a one-dimensional cavity wave in a 200nm nanowire

Abstract:
New engineering research at the University of Pennsylvania demonstrates that polaritons have increased coupling strength when confined to nanoscale semiconductors. This represents a promising advance in the field of photonics: smaller and faster circuits that use light rather than electricity.

Penn Researchers Break Light-Matter Coupling Strength Limit in Nanoscale Semiconductors

Philadelphia, PA | Posted on June 16th, 2011

The research was conducted by assistant professor Ritesh Agarwal, postdoctoral fellow Lambert van Vugt and graduate student Brian Piccione of the Department of Materials Science and Engineering in Penn's School of Engineering and Applied Science. Chang-Hee Cho and Pavan Nukala, also of the Materials Science department, contributed to the study.

Their work was published in the journal Proceedings of the National Academy of Sciences.

Polaritons are quasiparticles, combinations of physical particles and the energy they contribute to a system that can be measured and tracked as a single unit. Polaritons are combinations of photons and another quasiparticle, excitons. Together, they have qualities of both light and electric charge, without being fully either.

"An exciton is a combination of a an electron, which has negative charge and an electron hole, which has a positive charge. Light is an oscillating electro-magnetic field, so it can couple with the excitons," Agarwal said. "When their frequencies match, they can talk to one another; both of their oscillations become more pronounced."

High light-matter coupling strength is a key factor in designing photonic devices, which would use light instead of electricity and thus be faster and use less power than comparable electronic devices. However, the coupling strength exhibited within bulk semiconductors had always been thought of as a fixed property of the material they were made of.

Agarwal's team proved that, with the proper fabrication and finishing techniques, this limit can be broken.

"When you go from bulk sizes to one micron, the light-matter coupling strength is pretty constant," Agarwal said. "But, if you try to go below 500 nanometers or so, what we have shown is that this coupling strength increases dramatically."

The difference is a function of one of nanotechnology's principle phenomena: the traits of a bulk material are different than structures of the same material on the nanoscale.

"When you're working at bigger sizes, the surface is not as important. The surface to volume ratio — the number of atoms on the surface divided by the number of atoms in the whole material — is a very small number," Agarwal said. "But when you make a very small structure, say 100 nanometers, this number is dramatically increased. Then what is happening on the surface critically determines the device's properties."

Other researchers have tried to make polariton cavities on this small a scale, but the chemical etching method used to fabricate the devices damages the semiconductor surface. The defects on the surface trap the excitons and render them useless.

"Our cadmium sulfide nanowires are self-assembled; we don't etch them. But the surface quality was still a limiting factor, so we developed techniques of surface passivation. We grew a silicon oxide shell on the surface of the wires and greatly improved their optical properties," Agarwal said.

The oxide shell fills the electrical gaps in the nanowire surface, preventing the excitons from getting trapped.

"We also developed tools and techniques for measuring this light-matter coupling strength," Piccione said. "We've quantified the light-matter coupling strength, so we can show that it's enhanced in the smaller structures,"

Being able to quantify this increased coupling strength opens the door for designing nanophotonic circuit elements and devices.

"The stronger you can make light-matter coupling, the better you can make photonic switches," Agarwal said. "Electrical transistors work because electrons care what other electrons are doing, but, on their own, photons do not interact with each other. You need to combine optical properties with material properties to make it work"

This research was supported by the Netherlands Organization for Scientific Research Rubicon Programme, the U.S. Army Research Office, the National Science Foundation, Penn's Nano/Bio Interface Center and the National Institutes of Health.

####

For more information, please click here

Contacts:
Media Contact:
Evan Lerner

215-573-6604

Copyright © University of Pennsylvania

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

FEI Launches Helios G4 DualBeam Series for Materials Science: The Helios G4 DualBeam Series features new capabilities to enable scientists and engineers to answer the most demanding and challenging scientific questions June 27th, 2016

Superheroes are real: Ultrasensitive nonlinear metamaterials for data transfer June 25th, 2016

Russian physicists create a high-precision 'quantum ruler': Physicists have devised a method for creating a special quantum entangled state June 25th, 2016

Nanoscientists develop the 'ultimate discovery tool': Rapid discovery power is similar to what gene chips offer biology June 25th, 2016

Govt.-Legislation/Regulation/Funding/Policy

Nanoscientists develop the 'ultimate discovery tool': Rapid discovery power is similar to what gene chips offer biology June 25th, 2016

Ultrathin, flat lens resolves chirality and color: Multifunctional lens could replace bulky, expensive machines June 25th, 2016

Particle zoo in a quantum computer: First experimental quantum simulation of particle physics phenomena June 23rd, 2016

Titan shines light on high-temperature superconductor pathway: Simulation demonstrates how superconductivity arises in cuprates' pseudogap phase June 22nd, 2016

Possible Futures

Superheroes are real: Ultrasensitive nonlinear metamaterials for data transfer June 25th, 2016

Russian physicists create a high-precision 'quantum ruler': Physicists have devised a method for creating a special quantum entangled state June 25th, 2016

Nanoscientists develop the 'ultimate discovery tool': Rapid discovery power is similar to what gene chips offer biology June 25th, 2016

Nanotechnology and math deliver two-in-one punch for cancer therapy resistance June 24th, 2016

Academic/Education

JPK’s NanoWizard® AFM and ForceRobot® systems are being used in the field of medical diagnostics in the Supersensitive Molecular Layer Laboratory of POSTECH in Korea June 21st, 2016

Weizmann Institute of Science Presents: Weizmann Wonder Wander - 4G - is Online June 21st, 2016

NanoLabNL boosts quality of research facilities as Dutch Toekomstfonds invests firmly June 10th, 2016

The Institute for Transfusion Medicine at the University Hospital of Duisburg-Essen in Germany uses the ZetaView from Particle Metrix to quantify extracellular vesicles June 7th, 2016

Self Assembly

Self-assembling icosahedral protein designed: Self-assembling icosahedral protein designed June 22nd, 2016

DNA shaping up to be ideal framework for rationally designed nanostructures: Shaped DNA frames that precisely link nanoparticles into different structures offer a platform for designing functional nanomaterials June 14th, 2016

Automating DNA origami opens door to many new uses: Like 3-D printing did for larger objects, method makes it easy to build nanoparticles out of DNA May 30th, 2016

Searching for a nanotech self-organizing principle May 1st, 2016

Nanoelectronics

Soft decoupling of organic molecules on metal June 23rd, 2016

Tailored DNA shifts electrons into the 'fast lane': DNA nanowire improved by altering sequences June 22nd, 2016

Scientists engineer tunable DNA for electronics applications June 21st, 2016

Novel energy inside a microcircuit chip: VTT developed an efficient nanomaterial-based integrated energy June 10th, 2016

Discoveries

Superheroes are real: Ultrasensitive nonlinear metamaterials for data transfer June 25th, 2016

Russian physicists create a high-precision 'quantum ruler': Physicists have devised a method for creating a special quantum entangled state June 25th, 2016

Nanoscientists develop the 'ultimate discovery tool': Rapid discovery power is similar to what gene chips offer biology June 25th, 2016

Ultrathin, flat lens resolves chirality and color: Multifunctional lens could replace bulky, expensive machines June 25th, 2016

Photonics/Optics/Lasers

Superheroes are real: Ultrasensitive nonlinear metamaterials for data transfer June 25th, 2016

Russian physicists create a high-precision 'quantum ruler': Physicists have devised a method for creating a special quantum entangled state June 25th, 2016

Marrying superconductors, lasers, and Bose-Einstein condensates: Chapman University Institute for Quantum Studies (IQS) member Yutaka Shikano, Ph.D., recently had research published in Scientific Reports June 20th, 2016

A new trick for controlling emission direction in microlasers June 20th, 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







Car Brands
Buy website traffic