Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

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

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 23rd, 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:
Office of University Communications
200 Sansom Place East, 3600 Chestnut Street
Philadelphia, PA 19104-6106

Copyright © Penn State

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

Carbon nanotube optics poised to provide pathway to optical-based quantum cryptography and quantum computing: Researchers are exploring enhanced potential of carbon nanotubes for unique applications June 18th, 2018

Camouflaged nanoparticles used to deliver killer protein to cancer June 17th, 2018

Squeezing light at the nanoscale: Ultra-confined light could detect harmful molecules June 17th, 2018

Physicists devise method to reveal how light affects materials: The new method adds to the understanding of the fundamental laws governing the interaction of electrons and light June 15th, 2018

Govt.-Legislation/Regulation/Funding/Policy

Carbon nanotube optics poised to provide pathway to optical-based quantum cryptography and quantum computing: Researchers are exploring enhanced potential of carbon nanotubes for unique applications June 18th, 2018

Camouflaged nanoparticles used to deliver killer protein to cancer June 17th, 2018

Squeezing light at the nanoscale: Ultra-confined light could detect harmful molecules June 17th, 2018

Tripling the Energy Storage of Lithium-Ion Batteries: Scientists have synthesized a new cathode material from iron fluoride that surpasses the capacity limits of traditional lithium-ion batteries June 14th, 2018

Chip Technology

Carbon nanotube optics poised to provide pathway to optical-based quantum cryptography and quantum computing: Researchers are exploring enhanced potential of carbon nanotubes for unique applications June 18th, 2018

Making quantum puddles: Physicists discover how to create the thinnest liquid films ever June 13th, 2018

Leti Presenting Strategic Vision and Hosting a Workshop at SEMICON West: “From Electrons to Photons” Leti Workshop and CEO Media Briefing Set for Tuesday, July 10 in W Hotel, San Francisco June 12th, 2018

Nanometrics Updates Time of Webcast at Stifel 2018 Cross Sector Insight Conference June 12th, 2018

Optical computing/Photonic computing

Carbon nanotube optics poised to provide pathway to optical-based quantum cryptography and quantum computing: Researchers are exploring enhanced potential of carbon nanotubes for unique applications June 18th, 2018

Physicists devise method to reveal how light affects materials: The new method adds to the understanding of the fundamental laws governing the interaction of electrons and light June 15th, 2018

Leti Presenting Strategic Vision and Hosting a Workshop at SEMICON West: “From Electrons to Photons” Leti Workshop and CEO Media Briefing Set for Tuesday, July 10 in W Hotel, San Francisco June 12th, 2018

Switching with molecules: Molecular switch will facilitate the development of pioneering electro-optical devices May 25th, 2018

Discoveries

Carbon nanotube optics poised to provide pathway to optical-based quantum cryptography and quantum computing: Researchers are exploring enhanced potential of carbon nanotubes for unique applications June 18th, 2018

Camouflaged nanoparticles used to deliver killer protein to cancer June 17th, 2018

Squeezing light at the nanoscale: Ultra-confined light could detect harmful molecules June 17th, 2018

Physicists devise method to reveal how light affects materials: The new method adds to the understanding of the fundamental laws governing the interaction of electrons and light June 15th, 2018

Announcements

Carbon nanotube optics poised to provide pathway to optical-based quantum cryptography and quantum computing: Researchers are exploring enhanced potential of carbon nanotubes for unique applications June 18th, 2018

Camouflaged nanoparticles used to deliver killer protein to cancer June 17th, 2018

Squeezing light at the nanoscale: Ultra-confined light could detect harmful molecules June 17th, 2018

Physicists devise method to reveal how light affects materials: The new method adds to the understanding of the fundamental laws governing the interaction of electrons and light June 15th, 2018

Photonics/Optics/Lasers

Carbon nanotube optics poised to provide pathway to optical-based quantum cryptography and quantum computing: Researchers are exploring enhanced potential of carbon nanotubes for unique applications June 18th, 2018

Squeezing light at the nanoscale: Ultra-confined light could detect harmful molecules June 17th, 2018

New optical sensor can determine if molecules are left or right 'handed' June 13th, 2018

Leti Presenting Strategic Vision and Hosting a Workshop at SEMICON West: “From Electrons to Photons” Leti Workshop and CEO Media Briefing Set for Tuesday, July 10 in W Hotel, San Francisco June 12th, 2018

Research partnerships

Evidence for a new property of quantum matter revealed: Electrical dipole activity detected in a quantum material unlike any other tested June 11th, 2018

Scientists use photonic chip to make virtual movies of molecular motion June 6th, 2018

Quantum Interference May Be Key to Smaller Insulators: Breakthrough could jumpstart further miniaturization of transistors June 6th, 2018

Tunable diamond string may hold key to quantum memory: A process similar to guitar tuning improves storage time of quantum memory May 24th, 2018

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



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project