Their research is the latest in a series of recent findings related to how light and matter interact at the atomic scale, and it is the first to demonstrate that the material – a specially designed “meta-atom” of gold and silicon oxide – can transmit light through a wide bandwidth and at a speed approaching infinity. The meta-atoms’ broadband capability could lead to advances in optical devices, which currently rely on a single frequency to transmit light, the researchers say.
“These meta-atoms can be integrated as building blocks for unconventional optical components with exotic electromagnetic properties over a wide frequency range,” write Dr. Jie Gao and Dr. Xiaodong Yang, assistant professors of mechanical engineering at Missouri S&T, and Dr. Lei Sun, a visiting scholar at the university. The researchers describe their atomic-scale design in the latest issue of the journal Physical Review B (“Broadband epsilon-near-zero metamaterials with steplike metal-dielectric multilayer structures,” Phys. Rev. B 87, 165134 2013).
The researchers created mathematical models of the meta-atom, a material 100 nanometers wide and 25 nanometers tall that combined gold and silicon oxide in stairstep fashion. A nanometer is one billionth of a meter and visible only with the aid of a high-power electron microscope.
In their simulations, the researchers stacked 10 of the meta-atoms, then shot light through them at various frequencies. They found that when light encountered the material in a range between 540 terahertz and 590 terahertz, it “stretched” into a nearly straight line and achieved an “effective permittivity” known as epsilon-near-zero.
Effective permittivity refers to the ratio of light’s speed through air to its speed as it passes through a material. When light travels through glass, for instance, its effective permittivity is 2.25. Through air or the vacuum of outer space, the ratio is one. That ratio is what is typically referred to as the speed of light.
As light passes through the engineered meta-atoms described by Gao and Yang, however, its effective permittivity reaches a near-zero ratio. In other words, through the medium of these specially designed materials, light actually travels faster than the speed of light. It travels “infinitely fast” through this medium, Yang says.
The meta-atoms also stretch the light. Other materials, such as glass, typically compress optical waves, causing diffraction.
This stretching phenomenon means that “waves of light could tunnel through very small holes,” Yang says. “It is like squeezing an elephant through an ultra-small channel.”
The wavelength of light encountering a single meta-atom is 500 nanometers from peak to peak, or five times the length of Gao and Yang’s specially designed meta-atoms, which are 100 nanometers in length. While the Missouri S&T team has yet to fabricate actual meta-atoms, they say their research shows that the materials could be built and used for optical communications, image processing, energy redirecting and other emerging fields, such as adaptive optics.
Last year, Albert Polman at the FOM Institute for Atomic and Molecular Physics in Amsterdam and Nader Engheta, an electrical engineer at the University of Pennsylvania, developed a tiny waveguide device in which light waves of a single wavelength also achieved epsilon-near-zero. But the Missouri S&T researchers’ work is the first to demonstrate epsilon-near-zero in a broadband of 50 terahertz.
“The design is practical and realistic, with the potential to fabricate actual meta-atoms,” says Gao. Adds Yang: “With this research, we filled the gap from the theoretical to the practical.”
Through a process known as electron-beam deposition, the researchers have built a thin-film wafer from 13 stacked meta-atoms. But those materials were uniform in composition rather than arranged in the stairstep fashion of their modeled meta-atoms.
Andrew Careaga | EurekAlert!
Physics, photosynthesis and solar cells
01.12.2016 | University of California - Riverside
New process produces hydrogen at much lower temperature
01.12.2016 | Waseda University
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water
In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...
The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.
Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
02.12.2016 | Medical Engineering
02.12.2016 | Agricultural and Forestry Science
02.12.2016 | Physics and Astronomy