Video: Using off the shelf components German researchers made the first wireless video transmission in the terahertz range 鈥� potentially 1000 times faster than existing wireless technologies (Video courtesy Terahertz Communications Lab).
Video footage has been transmitted using a terahertz wireless signal for the first time. Although the link spanned just 22 meters it marks a significant step towards using much faster chunks of wireless spectrum, by harnessing radio waves oscillating a trillion times per second.
The speed at which wireless data can be transferred is limited by the vibration rate of radio waves. Today鈥檚 fastest wireless technologies, including WiFi and third generation (3G) mobile networks, operate in the ranges of gigahertz (a billion times per second) and megahertz (a million times a second) respectively.
Using terahertz bandwidth 鈥� which ranges from 300GHz to 3 terahertz (THz) 鈥� could offer a 1000 fold increase in transmission speed and should open up new frequencies for communication. The as yet untapped terahertz band of the electromagnetic spectrum lies between microwaves and visible light.
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Faster Futurama
鈥淚f you want to do very high rates of communication, you have to use terahertz frequencies,鈥� says Christian Jastrow of the in Braunschweig, Germany.
Terahertz waves are hard to generate because their frequency falls above those generated by microwave equipment and below those generated by lasers. Terahertz security scanners that see through a person鈥檚 clothes are easier because less fidelity is needed than for communications.
Until recently, terahertz frequencies have remained out of reach for those purposes. Now, Jastrow and colleagues have combined a series of commercially available frequency multipliers to make a 10 GHz microwave generator produce the lowest frequency of terahertz 鈥� a 300 GHz wave. A video (see right) shows a transmission of the television show Futurama using the system. Previous demonstrations of terahertz transfers has been much smaller scale and less data intensive than a video stream.
Using a specially designed high frequency transmitter and polyethylene lens, the researchers focus the waves into a relatively low-power beam that transmitted a video signal of up to 22 meters before it was absorbed by the earth鈥檚 atmosphere.
Jastrow says terahertz transmissions could improve video conferencing and make it possible to download complete movies and other large files in seconds rather than tens of minutes.
Scaling up
of the University of Utah, US, says the advance is 鈥渧ery impressive,鈥� but has its limits.
鈥淭hey did a nice job of showing something people have been trying to get to, and they did it using commercially available components,鈥� Nahata says. 鈥淏ut they can鈥檛 scale it up to 1 or more terahertz.鈥�
He notes that each time Jastrow鈥檚 team multiplied the microwave signal, they lost a significant amount of power, limiting the total increase in frequency achievable. To get around such limits, Nahata and others are experimenting with ultra-fast lasers as terahertz generators.
鈥淧eople are going to have to come up with other ways of doing this if they want to go to much higher frequencies,鈥� Nahata says. 鈥淲henever people think they have gone as fast as is necessary, that very quickly gets used up and people want more.鈥�
Journal Reference: Electronic Letters (doi: )