(Press-News.org) They said it could be done and now they've done it. What's more, they did it with a GRIN. A team of researchers with the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California, Berkeley, have carried out the first experimental demonstration of GRIN – for gradient index – plasmonics, a hybrid technology that opens the door to a wide range of exotic optics, including superfast computers based on light rather than electronic signals, ultra-powerful optical microscopes able to resolve DNA molecules with visible light, and "invisibility" carpet-cloaking devices.
Working with composites featuring a dielectric (non-conducting) material on a metal substrate, and "grey-scale" electron beam lithography, a standard method in the computer chip industry for patterning 3-D surface topographies, the researchers have fabricated highly efficient plasmonic versions of Luneburg and Eaton lenses. A Luneburg lens focuses light from all directions equally well, and an Eaton lens bends light 90 degrees from all incoming directions.
"This past year, we used computer simulations to demonstrate that with only moderate modifications of an isotropic dielectric material in a dielectric-metal composite, it would be possible to achieve practical transformation optics results," says Xiang Zhang, who led this research. "Our GRIN plasmonics technique provides a practical way for routing light at very small scales and producing efficient functional plasmonic devices."
Zhang, a principal investigator with Berkeley Lab's Materials Sciences Division and director of UC Berkeley's Nano-scale Science and Engineering Center (SINAM), is the corresponding author of a paper in the journal Nature Nanotechnology, describing this work titled, "Plasmonic Luneburg and Eaton Lenses." Co-authoring the paper were Thomas Zentgraf, Yongmin Liu, Maiken Mikkelsen and Jason Valentine.
GRIN plasmonics combines methodologies from transformation optics and plasmonics, two rising new fields of science that could revolutionize what we are able to do with light. In transformation optics, the physical space through which light travels is warped to control the light's trajectory, similar to the way in which outer space is warped by a massive object under Einstein's relativity theory. In plasmonics, light is confined in dimensions smaller than the wavelength of photons in free space, making it possible to match the different length-scales associated with photonics and electronics in a single nanoscale device.
"Applying transformation optics to plasmonics allows for precise control of strongly confined light waves in the context of two-dimensional optics," Zhang says. "Our technique is analogous to the well-known GRIN optics technique, whereas previous plasmonic techniques were realized by discrete structuring of the metal surface in a metal-dielectric composite."
Like all plasmonic technologies, GRIN plasmonics starts with an electronic surface wave that rolls through the conduction electrons on a metal. Just as the energy in a wave of light is carried in a quantized particle-like unit called a photon, so, too, is plasmonic energy carried in a quasi-particle called a plasmon. Plasmons will interact with photons at the interface of a metal and dielectric to form yet another quasi-particle, a surface plasmon polariton (SPP).
The Luneburg and Eaton lenses fabricated by Zhang and his co-authors interacted with SPPs rather than photons. To make these lenses, the researchers worked with a thin dielectric film (a thermplastic called PMMA) on top of a gold surface. When applying grey-scale electron beam lithography, the researchers exposed the dielectric film to an electron beam that was varied in dosage (charge per unit area) as it moved across the film's surface. This resulted in highly controlled differences in film thickness across the length of the dielectric that altered the local propagation of SPPs. In turn, the "mode index," which determines how fast the SPPs will propagate, is altered so that the direction of the SPPs can be influenced.
"By adiabatically tailoring the topology of the dielectric layer adjacent to the metal surface, we're able to continuously modify the mode index of SPPs," says Zentgraf. "As a result, we can manipulate the flow of SPPs with a greater degree of freedom in the context of two-dimensional optics."
Says Liu, "The practicality of working only with the purely dielectric material to transform SPPs is a big selling point for GRIN plasmonics. Controlling the physical properties of metals on the nanometer length-scale, which is the penetration depth of electromagnetic waves associated with SPPs extending below the metal surfaces, is beyond the reach of existing nanofabrication techniques."
Adds Zentgraf, "Our approach has the potential to achieve low-loss functional plasmonic elements with a standard fabrication technology that is fully compatible with active plasmonics."
In the Nature Nanotechnology paper, the researchers say that inefficiencies in plasmonic devices due to SPPs lost through scattering could be reduced even further by incorporating various SPP gain materials, such as fluorescent dye molecules, directly into the dielectric. This, they say, would lead to an increased propagation distance that is highly desired for optical and plasmonic devices. It should also enable the realization of two-dimensional plasmonic elements beyond the Luneburg and Eaton lenses.
Says Mikkelsen, "GRIN plasmonics can be immediately applied to the design and production of various plasmonic elements, such as waveguides and beam splitters, to improve the performance of integrated plasmonics. Currently we are working on more complex, transformational plasmonic devices, such as plasmonic collimators, single plasmonic elements with multiple functions, and plasmonic lenses with enhanced performance."
INFORMATION:
This research was supported by the U.S. Army Research Office and the National Science Foundation's Nano-scale Science and Engineering Center.
Lawrence Berkeley National Laboratory is a U.S. Department of Energy (DOE) national laboratory managed by the University of California for the DOE Office of Science. Berkeley Lab provides solutions to the world's most urgent scientific challenges including sustainable energy, climate change, human health, and a better understanding of matter and force in the universe. It is a world leader in improving our lives through team science, advanced computing, and innovative technology. Visit our Website at www.lbl.gov
GRIN plasmonics
A practical path to superfast computing, ultrapowerful optical microscopy and invisibility carpet-cloaking devices
2011-01-26
ELSE PRESS RELEASES FROM THIS DATE:
Women in Congress outperform men on some measures
2011-01-26
Congresswomen consistently outperform their male counterparts on several measures of job performance, according to a recent study by University of Chicago scholar Christopher Berry.
The research comes as the 112th Congress is sworn in this month with 89 women, the first decline in female representation since 1978. The study authors argue that because women face difficult odds in reaching Congress – women account for fewer than one in six representatives – the ones who succeed are more capable on average than their male colleagues.
Women in Congress deliver more federal ...
Legal restrictions compromise effectiveness of advance directives
2011-01-26
Current legal restrictions significantly compromise the clinical effectiveness of advance directives, according to a study by researchers at the University of California, San Francisco.
Advance directives allow patients to designate health care decision-makers and specify health care preferences for future medical needs. However, "the legal requirements and restrictions necessary to execute a legally valid directive prohibit many individuals from effectively documenting their end-of-life wishes," said lead author Lesley S. Castillo, BA, a geriatrics research assistant ...
Neurologists predict more cases of stroke, dementia, Parkinson's disease and epilepsy
2011-01-26
MAYWOOD, Ill. -- As the population ages, neurologists will be challenged by a growing population of patients with stroke, dementia, Parkinson's disease and epilepsy.
The expected increase in these and other age-related neurologic disorders is among the trends that Loyola University Health System neurologists Dr. José Biller and Dr. Michael J. Schneck describe in a January, 2011, article in the journal Frontiers in Neurology.
In the past, treatment options were limited for patients with neurological disorders. "Colloquially, the neurologist would 'diagnose and adios,'" ...
Preschool kids know what they like: Salt, sugar and fat
2011-01-26
EUGENE, Ore. -- (Jan. 25, 2011) -- A child's taste preferences begin at home and most often involve salt, sugar and fat. And, researchers say, young kids learn quickly what brands deliver the goods.
In a study of preschoolers ages 3 to 5, involving two separate experiments, researchers found that salt, sugar and fat are what kids most prefer -- and that these children already could equate their taste preferences to brand-name fast-food and soda products.
In a world where salt, sugar and fat have been repeatedly linked to obesity, waiting for children to begin school ...
Biologists' favorite worm gets viruses
2011-01-26
A workhorse of modern biology is sick, and scientists couldn't be happier.
Researchers at Washington University School of Medicine in St. Louis, the Jacques Monod Institute in France and Cambridge University have found that the nematode C. elegans, a millimeter-long worm used extensively for decades to study many aspects of biology, gets naturally occurring viral infections.
The discovery means C. elegans is likely to help scientists study the way viruses and their hosts interact.
"We can easily disable any of C. elegans' genes, confront the worm with a virus and ...
Possible new approach to treating a life-threatening blood disorder
2011-01-26
Thrombotic thrombocytopenic purpura (TTP) is a life-threatening disease of the blood system. The condition is caused by the presence of ultralarge multimers of the protein von Willebrand factor, which promote the formation of blood clots (thrombi) in small blood vessels throughout the body. Current treatments are protracted and associated with complications. However, a team of researchers, led by José López, at the Puget Sound Blood Center, Seattle, has generated data in mice that suggest that the drug N-acetylcysteine (NAC), which is FDA approved as a treatment for chronic ...
JCI table of contents: Jan. 25, 2011
2011-01-26
EDITOR'S PICK: Possible new approach to treating a life-threatening blood disorder
Thrombotic thrombocytopenic purpura (TTP) is a life-threatening disease of the blood system. The condition is caused by the presence of ultralarge multimers of the protein von Willebrand factor, which promote the formation of blood clots (thrombi) in small blood vessels throughout the body. Current treatments are protracted and associated with complications. However, a team of researchers, led by José López, at the Puget Sound Blood Center, Seattle, has generated data in mice that suggest ...
After stroke, admission to designated stroke center hospitals associated with reduced risk of death
2011-01-26
Patients who had an ischemic stroke and were admitted to hospitals designated as primary stroke centers had a modestly lower risk of death at 30 days, compared to patients who were admitted to non-designated hospitals, according to a study in the January 26 issue of JAMA.
Stroke is the leading cause of serious long-term disability and the third leading cause of death in the United States. Responding to the need for improvements in acute stroke care, the Brain Attack Coalition (BAC) published recommendations for the establishment of primary stroke centers in 2000, and ...
Occurrence of stroke after coronary artery bypass graft surgery appears to be decreasing
2011-01-26
An analysis of data on more than 45,000 patients who underwent coronary artery bypass graft (CABG) surgery at an academic medical center over the past 30 years finds that the occurrence of stroke after CABG has declined, despite an increase in risk profiles of patients, according to a study in the January 26 issue of JAMA.
Stroke is a devastating and potentially preventable complication of CABG surgery. Because it increasingly is being reserved for elderly patients with extensive coronary disease and co-existing conditions, prevalence of stroke after CABG is likely to ...
Cholera vaccination beneficial, post-outbreak
2011-01-26
Cholera vaccination beneficial, post-outbreak
Researchers newly report evidence that vaccination against cholera can be beneficial even after an outbreak has begun. Rita Reyburn, Dr. Lorenz von Seidlein, Dr. John Clemens and colleagues at the International Vaccine Institute (IVI) in Seoul, Korea analyze the impact that vaccination could have had on recent outbreaks around the globe in "The case for reactive mass oral cholera vaccinations", and Drs. Dang Duc Anh and Anna Lena Lopez and colleagues at IVI and in Vietnam report on the impact of such "reactive" use of vaccine ...
LAST 30 PRESS RELEASES:
A new discovery about the source of the vast energy in cosmic rays
Cancer ‘fingerprint’ can improve early detection
Rethinking the brain pacemaker: How better materials can improve signals
Allostatic load, educational attainment, and risk of cancer mortality among us men
Flaw in computer memory leads to global security fixes
Race, ethnicity, and sleep in us children
Geriatric surgery verification program can improve outcomes for older cancer patients in community hospitals
Pew funds 8 teams to conduct collaborative biomedical research
Finding innovative ways to address kidney cancer leads to DoD grant
Americans are uninformed about and undervaccinated for HPV
KTU scientists developed a nanolaser: silver nanocubes enable light generation
Insilico Medicine nominates orally available pre-clinical candidate targeting NLRP3 to treat inflammation and central nervous system diseases
PLOS receives $3.3 million grant to support Open Access publishing & business model transformation
HBx facilitates drug resistance in hepatocellular carcinoma via CD133-regulated self-renewal of liver cancer stem cells
ASN congratulates members for their role in the development of the Scientific Report of the 2025 Dietary Guidelines Advisory Committee
Late-stage breast cancer diagnosis on the rise in US
Brain volume changes seen in opioid users
Ultra-processed foods may drive colorectal cancer risk, USF-TGH study finds
Two Case Western Reserve University faculty members honored as Fellows of the National Academy of Inventors
How this cancer drug could make radiation a slam dunk therapy
National TRAP Program funds large-scale cleanup of discarded fishing gear
Using ‘biological age’ to predict early colorectal cancer risk
National Academy of Inventors announces Class of 2024 Fellows
SwRI showcases capabilities, evaluates novel fire-safety method with customized test
Caring for the emotional and spiritual needs of family members of ICU patients
Navigating crises: The financial adaptations of NGOs during the COVID-19 pandemic
Early life exposure to toxic chemicals may cause behavioral, psychological problems
AI predicts Earth’s peak warming
Risk of coronary artery disease in patients with liver cirrhosis: A systematic review and meta-analysis
Wild birds’ gut microbiome linked with its ornamentation and body condition
[Press-News.org] GRIN plasmonicsA practical path to superfast computing, ultrapowerful optical microscopy and invisibility carpet-cloaking devices