As reported in today's issue of the journal Nature, Intel researchers split a beam of light into two separate beams as it passed through silicon, and then used a novel transistor-like device to hit one beam with an electric charge, inducing a "phase shift." When the two beams of light are re-combined the phase shift induced between the two arms makes the light exiting the chip go on and off at over one gigahertz (one billion bits of data per second), 50 times faster than previously produced on silicon. This on and off pattern of light can be translated into the 1's and 0's needed to transmit data.
"This is a significant step toward building optical devices that move data around inside a computer at the speed of light," said Patrick Gelsinger, senior vice president and chief technology officer at Intel. "It is the kind of breakthrough that ripples across an industry over time enabling other new devices and applications. It could help make the Internet run faster, build much faster high-performance computers and enable high bandwidth applications like ultra-high-definition displays or vision recognition systems."
To date the fabrication of commercial optical devices has favored expensive and exotic materials requiring complex manufacturing, thus limiting their use to such specialty markets as wide area networks and telecommunications. Intel's fabrication of a fast silicon-based optical modulator with performance that exceeds 1 GHz demonstrates the viability of standard silicon as a material for bringing the benefits of high-bandwidth optics to a much wider range of computing and communications applications.
Inside Silicon, Light and Electronics Can Work Together
Silicon Photonics research at Intel began in the mid-1990s with efforts to test and measure transistors switching inside microprocessors optically. Although silicon appears opaque to the naked eye, it is transparent to infrared light.
"Just as Superman's X-ray vision allows him to see through walls, if you had infrared vision you could see through silicon," said Mario Paniccia, director of silicon photonics research at Intel. "This makes it possible to route infrared light in silicon, which is the same wavelength typically used for optical communications. The way electrical charges move around in a transistor when voltage is applied can be used to change the behavior of light as it passes through these charges. This led us to explore manipulating the properties of light, such as phase and amplitude, to produce silicon-based optical devices."
Why Bring Fiber Optics To The Chip?
Bandwidth. The 1GHz of today's experimental device equates to a billion bits of information traveling down a single fiber. Intel researchers think they can scale the technology up to 10GHz or faster in the future. A single photonic link can carry multiple, simultaneous data channels at the same speed by using different colors of light, just like multiple radio stations are transmitted to a car radio or hundreds of channels on a cable TV. Additionally, fiber-optic cables are immune to electro-magnetic interference and cross-talk, which makes traditional high-speed copper interconnects difficult to build.
"We have a long-term research program in place to explore how we can apply our silicon expertise in other areas with a long-term goal of developing integrated optical devices," Paniccia said.
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