Researchers design material that more effectively slows light

October 6, 2015 by Adam Jones
From left, graduate student Mohammad Parvinnezhad Hokmabadi, Dr. Patrick Kung, and Dr. Seongsin Margaret Kim work with the terahertz metamaterial in Shelby Hall.

Researchers at The University of Alabama designed and made a material that manipulates the speed of light in a new, more effective way than previous methods, according to findings recently published in Scientific Reports by the Nature Publishing Group.

The research by two professors and three grad students in the UA College of Engineering could help in creating next-generation optical networks and sensors that rely on variances in the speed of light.

"Slow light will lead to the development of optical buffers and delay lines as essential elements of future ultrafast all that could meet the ever-increasing demands for long-distance communications," said Dr. Seongsin Margaret Kim, associate professor of electrical and computer engineering and principal investigator on the research.

"In addition, enhanced interaction of photons with matter by lowering the speed of light gives rise to reduced power consumption in nonlinear optical switching devices and ultra-accurate sensing performance of optical sensors."

Besides Kim, the paper "Impact of Substrate and Bright Resonances on Group Velocity in Metamaterial without Dark Resonator" is authored by graduate students Mohammad Parvinnezhad Hokmabadi, Ju-Hyung Kim and Elmer Rivera along with Dr. Patrick Kung, an associate professor in electrical and computer engineering.

An emerging class of materials, metamaterials consist of specially designed metal patterns on the substrate, like silicon, whose size, geometry and orientation can be selected to allow for exotic optical properties The device fabricated by the UA researchers can be on both flexible substrate and silicon.

Parvinnezhad Hokmabadi, the lead author of the published paper, was partially supported by the UA Graduate Council Creative and Research Fellowship.

Kim's research investigates the interaction between light, a form of electromagnetic waves called photons, and matter to attain combined spectroscopic sensing and near field imaging capabilities by utilizing . Terahertz waves exist in the electromagnetic spectrum between infrared light and microwaves, and are promising for various applications such as security, chemical and biological sensing, biomedical imaging, and non-destructive manufacturing inspection.

For the experiment, the research group used terahertz waves, but the scientific findings can be applied to other wavelengths, including visible light, Kim said.

In unencumbered air, light is generally accepted to travel at a constant speed, but it can be slowed by passing through a material. Water, for instance, bends, or refracts, light. While the human eye can detect changes in the speed of light through bended images such as through eye glasses or curved mirrors, the speed of light is not substantially slower with simple refraction.

However, the phenomenon called "slow light" is a different sort of manipulation of the speed of light that can drastically slow and even stop light waves from travelling, thus reducing what's called the .

An emerging class of materials called metamaterials can be engineered with properties not found naturally, which can be structured to interact with light to slow or stop it. Unlike the best known methods for slowing that involved cold atoms, metamaterials use no energy and are much less complex to implement. They show promise in various applications such as filters, modulators, invisible cloaking devices, superlenses and perfect absorber.

In their lab at UA, the researchers fabricated and measured subwavelength metal patterns they specially designed on top of a substrate, such as silicon. Importantly, this metamaterial is flexible and thin. The main thrust of the paper is explaining how such a thin metamaterial can behave as if it was 1,000 times thicker, which makes highly integrated photonic sensors possible that could also be realized on flexible substrates.

"We have interests in using such a device in applications of sensing, communication and imaging," Kim said.

Explore further: Improving terahertz optics with efficient broadband antireflection coatings

More information: "Impact of Substrate and Bright Resonances on Group Velocity in Metamaterial without Dark Resonator." Scientific Reports 5, Article number: 14373 (2015). DOI: 10.1038/srep14373

Related Stories

Metamaterials shine bright as new terahertz source

April 23, 2015

Metamaterials allow design and use of light-matter interactions at a fundamental level. An efficient terahertz emission from two-dimensional arrays of gold split-ring resonator metamaterials was discovered as a result of ...

Slow light speeds up the microscopic world

September 17, 2015

A team of researchers from the University of St Andrews and the University of York has slowed down the speed of light in a process which could have major applications in fundamental science and medical diagnosis.

New way of retaining quantum memories stored in light

September 30, 2015

A team of Chinese physicists has now developed a way to confine light. This is significant because the approach allows quantum memories stored within photons to be retained. These findings stem from a study by Nan Sun from ...

Recommended for you

Understanding nature's patterns with plasmas

August 23, 2016

Patterns abound in nature, from zebra stripes and leopard spots to honeycombs and bands of clouds. Somehow, these patterns form and organize all by themselves. To better understand how, researchers have now created a new ...

Light and matter merge in quantum coupling

August 22, 2016

Where light and matter intersect, the world illuminates. Where light and matter interact so strongly that they become one, they illuminate a world of new physics, according to Rice University scientists.

Measuring tiny forces with light

August 25, 2016

Photons are bizarre: They have no mass, but they do have momentum. And that allows researchers to do counterintuitive things with photons, such as using light to push matter around.

Stretchy supercapacitors power wearable electronics

August 23, 2016

A future of soft robots that wash your dishes or smart T-shirts that power your cell phone may depend on the development of stretchy power sources. But traditional batteries are thick and rigid—not ideal properties for ...

Spherical tokamak as model for next steps in fusion energy

August 24, 2016

Among the top puzzles in the development of fusion energy is the best shape for the magnetic facility—or "bottle"—that will provide the next steps in the development of fusion reactors. Leading candidates include spherical ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

Billy_Madison
not rated yet Oct 06, 2015
Roll Tide

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.