laser (Juergen Faelchle/

Terahertz laser to power 'T-ray' vision and high-bandwidth communications

As the military, science agencies and communications firms compete for scarce spectrum resources, researchers at Harvard, MIT and the Army have developed a compact, room temperature, widely tunable terahertz laser that offers the potential for high-bandwidth communications, ultrahigh-resolution imaging and precise long-range sensing for radio astronomy. 

Until now, the terahertz section of the electromagnetic spectrum, which resides between microwaves and infrared and visible light, has been unavailable for most applications because current sources of terahertz frequencies are bulky, inefficient, have limited tuning or must operate at low temperature.

The new laser, however, is built from commercial, off-the-shelf components and can generate terahertz waves by spinning up the energy of molecules in nitrous oxide, commonly known as laughing gas.

Terahertz waves can be used in wireless communication, carrying information at a higher bandwidth than radar, across distances that scientists can now tune with the new device. The waves might also enable what MIT officials call "T-ray vision" -- the ability to see through clothing, book covers and other thin materials. Such technology could produce crisp, higher-resolution images than microwaves, and be far safer than X-rays.

"By tuning the terahertz frequency, you can choose how far the waves can travel through air before they are absorbed, from meters to kilometers, which gives precise control over who can 'hear' your terahertz communications or 'see' your terahertz radar," said MIT mathematics professor Steven Johnson. "Much like changing the dial on your radio, the ability to easily tune a terahertz source is crucial to opening up new applications in wireless communications, radar, and spectroscopy."

“There are many needs for a source like this laser, things like short range, high-bandwidth wireless communications, very high-resolution radar and spectroscopy,” said Henry Everitt, senior technologist with the Army Combat Capabilities Development Command Aviation & Missile Center and co-senior author of the paper. 

The lasers could be used for better skin and breast cancer imaging, drug detection, airport security and ultrahigh-capacity optical wireless links. 

"These gas lasers were for a long time seen as old technology, and people assumed these were huge, low-power, non-tunable things, so they looked to other terahertz sources," Johnson said. "Now we're saying they can be small, tunable, and much more efficient. You could fit this in your backpack, or in your vehicle for wireless communication or high-resolution imaging. Because you don't want a cyclotron in your car."

The research was published in the Journal Science.

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