Pitt and Bell Labs researchers send heavy photons over world-record distances
Unsurpassed exciton distances, lifetimes may lead to new form of optical communication
When light hits a semiconductor material and is absorbed, its photons can become "excitons," sometimes referred to as "heavy photons" because they carry energy, like photons, but have mass, like electrons. Excitons typically exist for only a short time--trillionths of a second--and travel only a few microns before turning back into photons, which are then emitted from the material.
In the June 10 issue of the journal Physical Review Letters, scientists from the University of Pittsburgh and Bell Labs, the R&D arm of Lucent Technologies, report that they have designed and demonstrated a two-dimensional semiconductor structure in which excitons exist longer and travel farther than previously recorded. In their paper, titled "Long-Distance Diffusion of Excitons in Double Quantum Well Structures," David Snoke, senior author and associate professor of physics and astronomy at Pitt, and his colleagues report a system in which excitons move freely over distances of hundreds of microns. Their findings open up the possibility of new applications, such as excitonic circuits.
The researchers "stretched out" the excitons by pulling them apart with an electrical field. This extended the excitons lifetimes by a million (up to 30 microseconds) and expanded the distances the excitons traveled (up to a millimeter). They were able to "see" the excitons by observing the emitted photons. The semiconductor structures designed in the experiment are of "world-record quality," said Snoke.
The ability to control excitons over long distances could lead to excitonic circuits in which photons are converted directly into excitons, which are then steered around a chip and converted back into photons again at a different location, such as an optical memory device, said Snoke. "Its another tool in our optics toolbox," he said.
"Were doing this with semiconductor circuits now designed for moving electrons," he added. "Its a completely new type of control over the system."
Other authors of the paper are Zoltan Voros and Ryan Balili, graduate students in Pitts Department of Physics and Astronomy, and Loren Pfeiffer and Kenneth West of Bell Labs.
Karen Hoffmann | EurekAlert!
The most recent press releases about innovation >>>
Die letzten 5 Focus-News des innovations-reports im Überblick:
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
Layered 2D material improves efficiency for solar cells and LEDs
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...