Engineers dare others to build a better terahertz multiplexer

"The biggest impact this may have is it may just be the kick that people need to start thinking about this issue," Daniel Mittleman says. "That means they'll start coming up with clever ideas that are entirely different from this one." (Credit: Jonny Hughes/Flickr)

Scientists and engineers have only recently started exploring the potential of terahertz waves for a new wireless network that can deliver data up to one hundred times faster than today’s cellular or Wi-Fi networks.

Now engineers say they may have solved one technical challenge: the first system for multiplexing terahertz waves.

terahertz multiplexer
Terahertz waves leak out of a small slit in the antenna at different angles, depending on frequency. The receiver can be tuned to select one angle, plucking a single data channel from a stream containing many channels. (Credit: Mittleman lab/Brown University)

Multiplexers are devices that enable separate streams of data to travel through a single medium. It’s the technology that makes it possible for a single cable to carry multiple TV channels or for a fiber optic line to carry thousands of phone calls at the same time.

“Any terahertz communications application is going to need some form of multiplexing and demultiplexing,” says Daniel Mittleman, professor of engineering at Brown University and senior author of a paper in Nature Photonics describing the new device. “This is, to our knowledge, the first time anyone has demonstrated a viable strategy for multiplexing in the terahertz range.”

How it works

The multiplexer that Mittleman and his colleagues have been working on makes use of what’s known as a leaky wave antenna. In this case, the antenna is made from two metal plates placed in parallel to form a waveguide. One of the plates has a small slit in it.

As terahertz waves travel down the waveguide, some of the radiation leaks out of the slit. It turns out that terahertz waves leak out a different angles depending on their frequency.

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“That means if you put in 10 different frequencies between the plates—each of them potentially carrying a unique data stream—they’ll come out at 10 different angles,” Mittleman says. “Now you’ve separated them and that’s demultiplexing.”

On the other end, a receiver could be tuned to accept radiation at a particular angle, thus receiving data from only one stream.

“We think it’s definitely a reasonable solution to meet the needs of a terahertz communication network,” says Nicholas Karl, a graduate student and the paper’s lead author. Karl led the experiments on the device with fellow graduate student Robert McKinney. Other authors on the study are Rajind Mendis, a research professor at Brown, and Yasuaki Monnai from Keio University in Tokyo.

‘The kick that people need’

One of the advantages to the approach, the researchers say, is that by adjusting the distance between the plates, it’s possible to adjust the spectrum bandwidth that can be allocated to each channel. That could be especially useful when such a device is deployed for use in a data network.

“For example, if one user suddenly needs a ton of bandwidth, you can take it from others on the network who don’t need as much just by changing the plate spacing at the right location,” Mittleman says.

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The group plans to continue its work to refine the device. A research group from Osaka University is collaborating with Mittleman’s group to implement the device in a prototype terahertz network they’re building.

“This is a first-generation, proof-of-concept device,” Karl says. “There are still things we can do to improve it, and we’ll continue to study it.”

Mittleman hopes the work will challenge other researchers to start developing components for terahertz networks.

“The biggest impact this may have is it may just be the kick that people need to start thinking about this issue,” Mittleman says. “That means they’ll start coming up with clever ideas that are entirely different from this one.”

The National Science Foundation and the W.M. Keck Foundation supported the project.

Source: Brown University