Intel claims quantum leap in fibre-optic detectors

Intel has developed silicon-based photoelectric detectors that could cut the cost of fibre-optic communications to a fraction of their current value.

Photodetectors — used in a range of applications, such as fibre-optic communications, image sensors, datacentre interconnects and optical drives — have been significantly more expensive than a copper-based equivalent.

According to Mario Paniccia, Intel fellow and director of Intel's photonics lab, this is due to the high cost of rare transition metals used in the optical devices.

"[Photonics] is today a technology predominately made with what we call exotic materials — indium phosphide, gallium arsenide, lithium molybdate — which involves expensive processing, very low volumes and, more importantly, very complex packaging and hand assembly," Paniccia said.

However, Intel claims to have found a way to create photodetectors using cheap silicon doped with a small layer of the element germanium, drastically reducing cost.

"Just to put it into context, a commercial [photodetector] that is used in telecoms typically sells for $200 to $300," Paniccia said. "We're talking devices that are probably an order or two in magnitude lower in cost." This prediction makes Intel's devices between 10 and 100 times cheaper than current photodetectors.

This lower cost opens up many applications, including making fibre to the home a great deal more accessible for consumers. The chief operating officer of Australian telecoms firm Tesltra, Greg Winn, recently explained this to ZDNet UK sister site ZDNet.com.au.

"If you run fibre, you need a device that breaks it down to the inside wiring, to the copper, and those devices are maybe a few hundred dollars," Winn said. "We do that today, but it's not economic to do it unless you're guaranteed the uptake of the services that the fibre requires."

In addition to lowering cost, Intel's new photodetectors have the advantage of being more sensitive, which may further reduce the price of fibre-optic communications. Paniccia said that, due to the increased sensitivity of the devices, they can transmit over a longer distance, or over the same distance with lower-power lasers.

The photodetectors, which are between 30 and 50 microns in size, work by multiplying the optical signals they receive.

Photodetectors work by capturing a photon (a quantised particle of light) that comes in and is absorbed by a material, which then converts a photon into electrical energy (an electron).

In Paniccia's avalanche photodetector, the electrical energy produced is amplified by a "multiplication layer", which uses ionisation to turn one photon into as many as 100 electrons. Those electrons then get separated by applying a voltage, which produces a current, similar to a solar cell.

Paniccia's team is currently able to demonstrate devices with speeds of up to 40Gbps, with as much as three times more performance (gain) than today's best detectors. However, the team has also been able to demonstrate devices with up to 200Gbps throughput.

"Now we have actually shown a device that far out performs anything in indium phosphide," he said. The device can be optimised for speed (Gbps), or efficiency over distance (metres per watt).

The work of Paniccia and his colleagues has been published in the journal Nature Photonics, and was conducted in conjunction with Darpa, Numonyx, the University of Virginia, and the University of California.