Berkeley researchers develop optical antenna for LEDs
Berkeley Lab researchers have developed a nano-sized optical antenna that can greatly enhance the spontaneous emission of light from atoms, molecules and semiconductor quantum dots. This advance opens the door to light-emitting diodes (LEDs) that can replace lasers for short-range optical communications, including optical interconnects for microchips, plus a host of other potential applications.
"Since the invention of the laser, spontaneous light emission has been looked down upon in favor of stimulated light emission," says Eli Yablonovitch, an electrical engineer with Berkeley Lab's Materials Sciences Division. "However, with the right optical antenna, spontaneous emissions can actually be faster than stimulated emissions."
Yablonovitch, who also holds a faculty appointment with the University of California (UC) Berkeley where he directs the NSF Center for Energy Efficient Electronics Science (E3S), and is a member of the Kavli Energy NanoSciences Institute at Berkeley (Kavli ENSI), led a team that used an external antenna made from gold to effectively boost the spontaneous light emission of a nanorod made from Indium Gallium Arsenide Phosphide (InGaAsP) by 115 times. This is approaching the 200-fold increase that is considered the landmark in speed difference between stimulated and spontaneous emissions. When a 200-fold increase is reached, spontaneous emission rates will exceed those of stimulated emissions.
"With optical antennas, we believe that spontaneous emission rate enhancements of better than 2,500 times are possible while still maintaining light emission efficiency greater than 50-percent," Yablonovitch says. "Replacing wires on microchips with antenna enhanced LEDs would allow for faster interconnectivity and greater computational power."
The results of this study are reported in the Proceedings of the National Academy of Sciences (PNAS) in a paper titled "Optical antenna enhanced spontaneous emission." Yablonovitch and UC Berkeley's Ming Wua are the corresponding authors. Co-authors are Michael Eggleston, Kevin Messer and Liming Zhang.
In the world of high technology lasers are ubiquitous, the reigning workhorse for high-speed optical communications. Lasers, however, have downsides for communications over short distances, i.e., one meter or less - they consume too much power and typically take up too much space. LEDs would be a much more efficient alternative but have been limited by their spontaneous emission rates.
"Spontaneous emission from molecular-sized radiators is slowed by many orders of magnitude because molecules are too small to act as their own antennas," Yablonovitch says. "The key to speeding up these spontaneous emissions is to couple the radiating molecule to a half-wavelength antenna. Even though we've had antennas in radio for 120 years, somehow we've overlooked antennas in optics. Sometimes the great discoveries are looking right at us and waiting."
For their optical antenna, Yablonovitch and his colleagues used an arch antenna configuration. The surface of a square-shaped InGaAsP nanorod was coated with a layer of titanium dioxide to provide isolation between the nanorod and a gold wire that was deposited perpendicularly over the nanorod to create the antenna. The InGaAsP semiconductor that served as the spontaneous light-emitting material is a material already in wide use for infrared laser communication and photo-detectors.
In addition to short distance communication applications, LEDs equipped with optical antennas could also find important use in photodetectors. Optical antennas could also be applied to imaging, bio-sensing and data storage applications.
This research was supported by E3S, the U.S. Air Force Office of Scientific Research, and the U.S. Department of Energy's Office of Science.
Lawrence Berkeley National Laboratory addresses the world's most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab's scientific expertise has been recognized with 13 Nobel prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy's Office of Science. For more, visit http://www.
Lynn Yarris | EurekAlert!
Researchers use light to remotely control curvature of plastics
23.03.2017 | North Carolina State University
TU Graz researchers show that enzyme function inhibits battery ageing
21.03.2017 | Technische Universität Graz
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...
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...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
23.03.2017 | Life Sciences
23.03.2017 | Power and Electrical Engineering
23.03.2017 | Earth Sciences