"Leaky" antennas could allow future wireless communications systems operating in the terahertz region to send and receive multiple signals. A prototype developed at Brown University is said to be the first system capable of multiplexing terahertz waves, which offer potentially much greater communications bandwidth than the microwaves used today in cellular and Wi-Fi networks. Multiplexers are devices that enable separate streams of data to travel through a single medium. The technology 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. The multiplexer developed at Brown is made from two metal plates placed in parallel to form a waveguide. One of the plates has a small slit in it, which allows some of the radiation traveling down the waveguide to leak out. Different signals leak out at different angles depending on their frequency. A leaky wave antenna separates terahertz waves by frequency. The device provides a viable multiplexing and demultiplexing strategy for future terahertz data networks, which have the potential to deliver data many times faster than today's cellular or Wi-Fi networks. Courtesy of the Mittleman Lab/Brown University. "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," said Brown engineering professor Daniel Mittleman. "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. 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 said. A research group from Osaka University is collaborating with Mittleman's group to implement the device in a prototype terahertz network. Funding came from the National Science Foundation and W.M. Keck Foundation. The research was published in Nature Photonics (doi: 10.1038/nphoton.2015.176).