IBM Announces Device for On-Chip Silicon Photonics

IBM researchers say they have created the fastest nanophotonic avalanche photodetector, a key element in the development of technology to use pulses of light rather than traditional copper wires for chip-to-chip communication. Researchers say silicon photonics technology will lead to faster, more energy-efficient computing.

IBM researchers have taken their latest steps in their efforts to enable chips to communicate via pulses of light rather than copper wires, a transition that could boost the performance and speed of computers while greatly improving energy efficiency.

IBM officials March 3 announced an advancement in the development of a nanophotonic avalanche photodetector. The device, which takes light and converts it into electricity, is the fastest of its kind, according to IBM researchers, receiving optical information signals at 40G bps and multiplying them by 10.

It also consumes less power than similar devices, running on a 1.5V voltage supply, which IBM says is 20 times smaller than what they've demonstrated in the past.

"This invention brings the vision of on-chip optical interconnections much closer to reality," T.C. Chen, vice president of science and technology at IBM Research, said in a statement. "With optical communications embedded into the processor chips, the prospect of building power-efficient computer systems with performance at the exaflop level might not be a very distant future."

IBM researchers are publishing their findings in the latest issue of Nature magazine. A video of IBM's findings can be seen here.

IBM, Intel and others are looking to develop on-chip components that use light to transmit data rather than the copper wiring found in traditional electrical interconnects. Industry observers say that given the speed and energy efficiency improvements promised by the technology, the development of optical communication devices will be a key to the way computers are built and operated over the next decade.

With major chip vendors such as Intel, Advanced Micro Devices and IBM-and even newer processor makers, such as Tilera-rapidly adding a greater number of processing cores onto a CPU, the need to improve the speed of data moving between the chips in a system, or between the servers themselves, is increasing.

Telecommunication companies already are replacing traditional telephone lines with fiber optic cables. The goal now is to shrink that capability so that the photonics can be used at the microprocessor level.

That is why other tech vendors also are working to develop optical communication devices for computer chips. Intel has been developing such technology for about seven years, and in December 2008 unveiled its own avalanche photodetector device.

Other companies, such as Luxtera, also are working on such technology. In August 2007, Luxtera rolled out Blazar, a 40GB optical cable for use in HPC (high-performance computing) environments.

A key in the efforts of both IBM and Intel is the use of silicon and germanium in creating the avalanche photodetector devices. Both silicon and germanium are currently used in developing current processors, which will make it easier and cheaper to develop, rather than using other kinds of materials to build the components. The devices also are made with standard chip-manufacturing processes, according to IBM.

The avalanche photodetector works in a way described by its name, according to IBM. Like an avalanche on the slope of a mountain, a light pulse at first frees up a few charge carriers, which then frees up other charge carriers, creating an avalanche effect until the original signaled is amplified many times over.

The IBM device does this faster than that of others, taking place within a few tens of nanometers.

"This dramatic improvement in performance is the result of manipulating the optical and electrical properties at the scale of just a few tens of atoms to achieve performance well beyond accepted boundaries," Solomon Assefa, a research staff member for IBM Research and the lead author on the paper, said in a statement. "These tiny devices are capable of detecting very weak pulses of light and amplifying them with unprecedented bandwidth and minimal addition of unwanted noise."

IBM's announcement is the latest in a series made in the vendor's building of what researchers are calling the "nanophotonics toolbox" of devices.

In 2006, IBM Research unveiled a silicon nanophotonic delay line, and a year later announced the development of a very compact silicon electro-optic modulator, for converting electrical signals into pulses of light.

In March 2008, IBM announced what researchers said was the world's smallest nanophotonic switch for directing traffic in on-chip optical communications.