As more and more Internet users log on, Internet cables are becoming overloaded.

New technologies are necessary to avoid a "bandwidth explosion." One of those technologies is called free-space optical communication, or FSO. Instead of optical fibers, FSO communication technologies transmit data wirelessly through the air.

Until now, FSO technology has relied mostly on near-infrared light to transmit information. But near-infrared wavelengths are harmful to the human eye and are easily slowed and scattered by the atmosphere.

Mid-wavelength infrared radiation promises to solve those problems. The radiation is harmless and is unaffected by smog, fog, haze, smoke or clouds of any kind.

Researchers at Northwestern University have developed a photodetector that is sensitive to mid-wavelength infrared. The device can receive information sent by a phototransistor, a cross between electronic transistor and optoelectronic photodiode that sends out mid-wavelength infrared radiation.

By sending information safely and effectively through free space, communications engineers can lighten the bandwidth burden currently shouldered by fiber-optic cables.

"For the first time, we have demonstrated a phototransistor that is totally made of an artificial semiconductor," Manijeh Razeghi, a professor of electrical engineering and computer science at Northwestern, said in a news release. "This extremely sensitive device could be a game changer for FSO communication technology by providing low-cost, high-speed data links."

Researchers detailed the new technology in the journal Applied Physics Letters.