Original URL: http://www.theregister.co.uk/2006/03/22/mit_photon_detector/

Broadband possible in space

Nobody tell BT

By Christopher Williams

Posted in Data Networking, 22nd March 2006 11:34 GMT

If humanity does ever colonise the wintry wastes of Mars, at least between having their faces sucked and uncovering Total Recall conspiracies, pioneers will be able to console themselves with eyeball-meltingly explicit broadband video feeds.

Researchers at MIT have made the possibility of high-speed optical communications in space a more realistic one by near-trebling the efficiency of a nanotech-based photon detector, New Scientist reports.

Co-author of the study Karl Berggren, publishing in the journal Optical Express, explained: “It can take hours with the existing wireless radio frequency technology to get useful scientific information back from Mars to Earth. But an optical link can do that thousands of times faster.”

The team cranked-up the sensitivity of their detector by giving it an anti-reflective coating to reduce light bouncing away and a 'photon trap' consisting of a cavity between a sheet of glass and a titanium and gold mirror which concentrates the signal on the detector.

The photon-detecting component itself is an extremely thin nanowire made from the nitride of the transition metal niobium.

Berggren says the function of the detector comes from the super conducting properties of the nanowire. It has zero electrical resistance when cooled to near absolute zero. During the experiments the detector was operated at just 1.8 degrees Kelvin, or about -456 degrees Fahrenheit. Because it has such low resistance, when even a single photon hits it a tiny electrical current is generated.

Interplanetary distances mean that even high-powered lasers would spread out and be hard to detect. The MIT group's improvements to the efficiency of the receiver – raising it from 20 per cent to 57 per cent - means even an extremely weak optical signal can be recognised.

NASA's canned Mars Telecomunications Orbiter was set to carry a beam capable of transferring 30 million bits per second. By comparison Mars Odyssey, which reached the Red Planet in 2002, manages a glacial 128,000 bits per second.®