Nav: Home

Researchers develop new lens for terahertz radiation

March 14, 2016

PROVIDENCE, R.I. [Brown University] -- Terahertz radiation is a relatively unexplored slice of the electromagnetic spectrum, but it holds the promise of countless new imaging applications as well as wireless communication networks with extremely high bandwidth. The problem is that there are few off-the-shelf components available for manipulating terahertz waves.

Now, researchers from Brown University's School of Engineering have developed a new type of lens for focusing terahertz radiation (which spans from about 100 to 10,000 GHz). The lens, made from an array of stacked metal plates with spaces between them, performs as well or better than existing terahertz lenses, and the architecture used to build the device could set the stage for a range of other terahertz components that don't currently exist.

The work was led by Rajind Mendis, assistant professor of engineering (research) at Brown, who worked with Dan Mittleman, professor of engineering at Brown. The work is described in the journal Nature Scientific Reports.

"Any photonic system that uses terahertz - whether it's in imaging, wireless communications or something else - will require lenses," said Dan Mittleman, professor of engineering at Brown and the senior author on the new paper. "We wanted to look for new ways to focus terahertz radiation."

Most lenses use the refractive properties of a material to focus light energy. Eyeglasses, for example, use convex glass to bend visible light and focus it on a certain spot. But for this new terahertz lens, the properties of the materials used don't matter as much as the way in which the materials are arranged.

"It's the architecture here that's important," Mendis said.

The new device is made from 32 metal plates, each 100 microns thick, with a 1-millimeter space between each plate. The plates have semicircular notches of different sizes cut out of one edge, such that when stacked horizontally the notches form a three-dimensional divot on one side of the device. When a terahertz beam enters the input side of the device, slices of the beam travel through the spaces between the plates. The concave output side of the device bends the beam slices to varying degrees such that the slices are all focused on a certain point.

Using the configuration developed for this new study, the researchers were able to focus a two-centimeter-diameter terahertz beam down to a four-millimeter spot. The radiation transmission through the device - the amount of radiation that makes it through the spaces as opposed to reflected back toward the source or dissipated inside the device - was about 80 percent. That's significantly better than silicon lenses, which typically have a transmission loss of about 50 percent, and about the same as lenses made from Teflon.

The new device has some advantages over existing Teflon lenses, however. In particular, by changing the spacing between the plates, the new device can be calibrated for specific terahertz wavelengths, something that isn't possible with existing lenses.

"That can be particularly interesting if you want to image things at one frequency and not at others," Mittleman said. "One of the important things here is that this design offers you a versatility that a simple chunk of plastic with a curved surface doesn't offer."

The work also suggests that the technique of using spaced metal plates to manipulate terahertz radiation could be useful in making other types of components that currently don't exist. Since a metallic architecture mimics a plastic (a dielectric), this material technology is called "artificial dielectrics."

"As much as anything else, this paper proves that the technology is feasible," Mittleman said. "Now we can go and make devices that are totally new in the terahertz world."

The same technology could be used, Mendis said, to make a polarizing beam splitter for terahertz waves - a device that separates waves according to their polarization state. Such a device could be used to implement elementary logic gates for terahertz photonic systems, where the binary (one and zero) logic states are assigned to the two polarization states. That would be an essential component of a terahertz data network.

"The spirit of this work is to develop a new technology for building terahertz components that might be alternatives to things that exist or that might be new," Mittleman said. "That's important for the terahertz field because there aren't a lot of off-the-shelf components yet."
-end-
Other authors on the paper were Masaya Nagai (professor at Osaka University in Japan), Yiqiu Wang (undergraduate student at Rice University) and Nicholas Karl (doctoral student at Brown).

The study was funded by the National Science Foundation and the Keck Foundation.

Note to Editors:

Editors: Brown University has a fiber link television studio available for domestic and international live and taped interviews, and maintains an ISDN line for radio interviews. For more information, call (401) 863-2476.

Brown University

Related Engineering Articles:

Engineering the meniscus
Damage to the meniscus is common, but there remains an unmet need for improved restorative therapies that can overcome poor healing in the avascular regions.
Artificially engineering the intestine
Short bowel syndrome is a debilitating condition with few treatment options, and these treatments have limited efficacy.
Reverse engineering the fireworks of life
An interdisciplinary team of Princeton researchers has successfully reverse engineered the components and sequence of events that lead to microtubule branching.
New method for engineering metabolic pathways
Two approaches provide a faster way to create enzymes and analyze their reactions, leading to the design of more complex molecules.
Engineering for high-speed devices
A research team from the University of Delaware has developed cutting-edge technology for photonics devices that could enable faster communications between phones and computers.
Breakthrough in blood vessel engineering
Growing functional blood vessel networks is no easy task. Previously, other groups have made networks that span millimeters in size.
Next-gen batteries possible with new engineering approach
Dramatically longer-lasting, faster-charging and safer lithium metal batteries may be possible, according to Penn State research, recently published in Nature Energy.
What can snakes teach us about engineering friction?
If you want to know how to make a sneaker with better traction, just ask a snake.
Engineering a plastic-eating enzyme
Scientists have engineered an enzyme which can digest some of our most commonly polluting plastics, providing a potential solution to one of the world's biggest environmental problems.
A new way to do metabolic engineering
University of Illinois researchers have created a novel metabolic engineering method that combines transcriptional activation, transcriptional interference, and gene deletion, and executes them simultaneously, making the process faster and easier.
More Engineering News and Engineering Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Rethinking Anger
Anger is universal and complex: it can be quiet, festering, justified, vengeful, and destructive. This hour, TED speakers explore the many sides of anger, why we need it, and who's allowed to feel it. Guests include psychologists Ryan Martin and Russell Kolts, writer Soraya Chemaly, former talk radio host Lisa Fritsch, and business professor Dan Moshavi.
Now Playing: Science for the People

#538 Nobels and Astrophysics
This week we start with this year's physics Nobel Prize awarded to Jim Peebles, Michel Mayor, and Didier Queloz and finish with a discussion of the Nobel Prizes as a way to award and highlight important science. Are they still relevant? When science breakthroughs are built on the backs of hundreds -- and sometimes thousands -- of people's hard work, how do you pick just three to highlight? Join host Rachelle Saunders and astrophysicist, author, and science communicator Ethan Siegel for their chat about astrophysics and Nobel Prizes.