The Best Photon Detector Yet

Cheap, high-performing detectors could boost Internet bandwidth and speed up computers.

Silicon is used throughout the electronics industry to make countless components and devices. This cheap and abundant chemical could also be about to transform the photonics industry, by making vital communication equipment cheaper and better. Engineers have already made a number of optical devices with silicon. On Sunday, researchers at Intel announced another significant advance: a silicon-based photodetector that achieves higher speed and sensitivity than other devices, including those made using exotic, expensive materials.

Avalanche array: The circles shown in the above array are silicon photodetectors fabricated at Intel. The detectors were made different sizes so that the researchers could compare their performance. Credit: Intel

Multimedia   Watch Mario Paniccia, director of Intel's Photonics Technology Lab, describe the new detector.

Light detectors are typically made of III-V semiconductors--materials composed of multiple elements such as indium and phosphorous. Although these semiconductors have great optical properties, they are more difficult to manufacture in high quantities than silicon, which makes them expensive. In the quest to make silicon photonics a reality and to match III-V semiconductor performance, researchers have sought to exploit the way electrons behave in silicon. And Intel's research, detailed yesterday in Nature Photonics, shows that silicon can make a detector that goes above and beyond expectations.

"This is the first time a silicon photonics device has [shown] better performance than any recorded for a III-V-based material," says Mario Paniccia, an Intel fellow and director of the company's photonics technology lab in Santa Clara, CA.

Detectors are crucial components in optical networks, receiving information transmitted via the light sent through fiber optic cable. Previously, Intel has built silicon-hybrid lasers, silicon-based modulators (which encode data on light), and detectors that use silicon as a channel to guide light.

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Intel's new device is based on a pre-existing design: an avalanche photodetector. In this type of detector, light is received and amplified by electron behavior within the material used. Avalanche photodetectors are found inside bulky optical networking equipment and currently cost $200 to $300 dollars apiece. If these detectors could be made out of silicon, Paniccia says they could cost less than $10. This would translate into higher bandwidth at cheaper prices and make it feasible to add optical networking to computers themselves, replacing the slow copper wiring that connects circuit boards and microchips with superfast optical connectors.

A simple photodetector converts photons to electricity similar to a solar cell. Once inside the detector, a photon creates a quasi-particle made up of a negatively charged electron and positively charged "hole" (an electron vacancy). When voltage is applied to the detector, the electron and the hole separate, producing an electrical current. The characteristics of this current can reveal information encoded onto the light.