(Press-News.org) WASHINGTON, D.C., August 4, 2015 -- Terahertz radiation, the no-man's land of the electromagnetic spectrum, has long stymied researchers. Optical technologies can finagle light in the shorter-wavelength visible and infrared range, while electromagnetic techniques can manipulate longer-wavelength radiation like microwaves and radio waves. Terahertz radiation, on the other hand, lies in the gap between microwaves and infrared, whether neither traditional way to manipulate waves works effectively. As a result, creating coherent artificial sources of terahertz radiation in order to harness it for human use requires some ingenuity.
Difficulties of generating it aside, terahertz radiation has a wide variety of potential applications, particularly in medical and security fields. Because it's a non-ionizing form of radiation, it is generally considered safe to use on the human body. For instance, it can distinguish between tissues of different water content or density, making it a potentially valuable tool for identifying tumors. It could also be used to detect explosives or hidden weapons, or to wirelessly transmit data.
In a step towards more widespread use of terahertz radiation, researchers have designed a new device that can convert a DC electric field into a tunable source of terahertz radiation. Their results are published this week in the Journal of Applied Physics, from AIP Publishing.
This device exploits the instabilities in the oscillation of conducting electrons at the device's surface, a phenomenon known as surface plasmon resonance. To address the terahertz gap, the team created a hybrid semiconductor: a layer of thick conducting material paired with two thin, two-dimensional crystalline layers made from graphene, silicene (a graphene-like material made from silicon instead of carbon), or a two-dimensional electron gas. When a direct current is passed through the hybrid semiconductor, it creates a plasmon instability at a particular wavenumber. This instability induces the emission of terahertz radiation, which can be harnessed with the help of a surface grating that splits the radiation.
By adjusting various parameters -- such as the density of conduction electrons in the material or the strength of the DC electric field -- it is possible to tune the cutoff wavenumber and, consequently, the frequency of the resulting terahertz radiation.
"[Our work] demonstrates a new approach for efficient energy conversation from a dc electric field to coherent, high-power and electrically tunable terahertz emission by using hybrid semiconductors," said Andrii Iurov, a researcher with a dual appointment at the University of New Mexico's Center for High Technology Materials and the City University of New York. "Additionally, our proposed approach based on hybrid semiconductors can be generalized to include other novel two-dimensional materials, such as hexagonal boron nitride, molybdenum disulfide and tungsten diselenide."
Other labs have created artificial sources of terahertz radiation, but this design could enable better imaging capabilities than other sources can provide. "Our proposed devices can retain the terahertz frequency like other terahertz sources but with a much shorter wavelength for an improved spatial resolution in imaging application as well as a very wide frequency tuning range from a microwave to a terahertz wave," said Iurov.
INFORMATION:
The article, "Tunable surface plasmon instability leading to emission of radiation," is authored by Godfrey Gumbs, Andrii Iurov, Danhong Huang, and Wei Pan. It will appear in the Journal of Applied Physics on August 4, 2015. After that date, it can be accessed at: http://scitation.aip.org/content/aip/journal/jap/118/5/10.1063/1.4927101
The authors of this paper are affiliated with City University of New York, Donostia International Physics Center, Center for High Technology Materials at University of New Mexico, Air Force Research Laboratory and Sandia National Laboratory.
ABOUT THE JOURNAL
The Journal of Applied Physics is an influential international journal publishing significant new experimental and theoretical results of applied physics research. See: http://jap.aip.org
WASHINGTON, D.C., August 4, 2015 -- Studies of the impact a droplet makes on solid surfaces hark back more than a century. And until now, it was generally believed that a droplet's impact on a solid surface could always be separated into two phases: spreading and retracting.
But it's much more complex than that, as a team of researchers from City University of Hong Kong, Ariel University in Israel, and Dalian University of Technology in China report in the journal Applied Physics Letters, from AIP Publishing.
"During the spreading phase, the droplet undergoes an inertia-dominant ...
UBC scientists have opened the doors to new research into malnutrition by creating an animal model that replicates the imbalance of gut bacteria associated with the difficult-to-treat disease.
Malnutrition affects millions of people worldwide and is responsible for one-fifth of deaths in children under the age of five. Children can also experience impaired cognitive development and stunted growth.
The problem arises when people don't have enough food to eat and their diet lacks proper nutrients. The disease also has a lot to do with environmental factors and it has ...
In vitro studies of the cellular effects of modeled osteopathic manipulative therapy (OMT) provide proof of concept for the manual techniques practiced by doctors of osteopathic medicine (DOs), according to researchers from the University of Arizona College of Medicine - Phoenix.
The study, published in The Journal of the American Osteopathic Association, focused on modeling two common OMT techniques, myofascial release and counterstrain. Researchers subjected fibroblast matrices to various strains and employed a scratch wound strain model to test the ability of OMT ...
A new strain of yeast called Yarrowia lipolytica Y-3492 was found to be very active in waste water treatment. The discovery was made by by microbiologists from Kazan Federal University during their research at Western Siberian peat bogs.
The strain is said to be effective against nitro compounds which are used in explosives, herbicides, insecticides, polymers, dyes, and some medications. Oil refineries and military equipment plants produce especially high amounts of such waste. The research was conducted with the use of widely known trinitrotoluene (TNT).
It is well-known ...
COLLEGE STATION -- It's happy hour at a lab in College Station. The cocktail of choice, developed by scientists with Texas A&M AgriLife Research, is one that stops or prevents the deadly Pierce's disease on wine grapes.
The discovery could turn a new leaf on the multimillion-dollar U.S. wine industry. Hear, hear.
The study, published in the academic journal PLOS ONE, describes the use of four bacteriophages that were identified for their ability to attack the bacteria that causes the devastating disease in grapes and several other plants.
A bacteriophage, or phage, ...
A paper from the University of Exeter has highlighted the dangers of relying on climate-based projections of future crop pest distributions and suggests that rapid evolution can confound model results.
Crop pests and pathogens are destructive organisms which pose a huge threat to food security and land management across the world. Much research has been carried out into why the pests are spreading, where they are likely to establish next, what damage they will do and what can be done to reduce their impact.
In a new synthesis, published today in the Annual Review of ...
Diagnosis of deadly brain conditions could be helped by new research that shows how infectious proteins that cause the disease spread.
The study reveals how the proteins - called prions - spread from the gut to the brain after a person or animal has eaten contaminated meat.
Scientists say their findings could aid the earlier diagnosis of prion diseases - which include variant Creutzfeldt-Jakob disease (vCJD) in people and bovine spongiform encephalopathy (BSE) in cows.
In people, the disease remains very rare - 229 people have died from vCJD since it was first identified ...
The Society of Thoracic Surgeons, the Society of Cardiovascular Anesthesiologists, and the American Society of ExtraCorporeal Technology have released a set of clinical practice guidelines to address management of a patient's temperature during open heart surgery. The guidelines appear in the August issue of The Annals of Thoracic Surgery and were published simultaneously in two other journals.
Numerous strategies are currently used to optimally manage the practice of cooling the blood, temperature maintenance (control of body temperature during surgery), and rewarming ...
This news release is available in French. While it is already possible to obtain in vitro pluripotent cells (ie, cells capable of generating all tissues of an embryo) from any cell type, researchers from Maria-Elena Torres-Padilla's team have pushed the limits of science even further. They managed to obtain totipotent cells with the same characteristics as those of the earliest embryonic stages and with even more interesting properties. Obtained in collaboration with Juanma Vaquerizas from the Max Planck Institute for Molecular Biomedicine (Münster, Germany), these ...
Women who exercised during their teen years were less likely to die from cancer and all other causes during middle-age and later in life, according to a new study by investigators at Vanderbilt University Medical Center and the Shanghai Cancer Institute in China.
The study was published online July 31 in Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association of Cancer Research.
Lead author Sarah Nechuta, Ph.D., MPH, assistant professor of Medicine in the Vanderbilt Epidemiology Center, said understanding the long-term impact of modifiable ...