This packaged electronic-photonic processor microchip under illumination reveals the chip’s primary features. The light rays emanating from the chip are drawn to show that the processor talks to the outside world using light. Credit: Glenn J. Asakawa, University of Colorado Read more at: http://phys.org/news/2015-12-demo-processor-ultrafast.html#jCp
Engineers have successfully married electrons and photons within a single-chip microprocessor, a landmark development that opens the door to ultrafast, low-power data crunching. The researchers packed 2 processor cores with >70 million transistors and 850 photonic components onto a 3-by-6-millimeter chip. They fabricated the microprocessor in a foundry that mass-produces high-performance computer chips, proving that their design can be easily and quickly scaled up for commercial production.
The new chip marks the next step in the evolution of fiber optic communication technology by integrating into a microprocessor the photonic interconnects, or inputs and outputs (I/O), needed to talk to other chips. “This is a milestone. It’s the first processor that can use light to communicate with the external world,” said A/Prof. Vladimir Stojanović. “No other processor has the photonic I/O in the chip.”
“This is the first time we’ve put a system together at such scale, and have it actually do something useful, like run a program,” said Asanović, who helped develop the free and open architecture called RISC-V (reduced instruction set computer), used by the processor.
Raw, high-resolution photo of the chip, with all chip electrical and photonic features clearly visible. Photo taken under microscope at the UC Berkeley Marvell Nanofabrication Laboratory. Credit: Chen Sun, with help from Sangyoon Han Read more at: http://phys.org/news/2015-12-demo-processor-ultrafast.html#jCp
Compared with electrical wires, fiber optics support greater bandwidth, carrying more data at higher speeds over greater distances with less energy. They showed that the chip had a bandwidth density of 300 gigabits/s/sq mm, ~10 – 50X greater than packaged electrical-only microprocessors on the market.
The photonic I/O on the chip is also energy-efficient, using only 1.3 picojoules per bit = 1.3 watts of power to transmit a terabit of data per second. In the experiments, the data was sent to a receiver 10m away and back.
The achievement opens the door to a new era of bandwidth-hungry applications. One near-term application for this technology is to make data centers more green. According to the Natural Resources Defense Council, data centers consumed about 91 billion kilowatt-hours of electricity in 2013, about 2% of the total electricity consumed in the US, and the appetite for power is growing exponentially.
Other APPS: They could be used in LIDAR, the light radar technology used to guide self-driving vehicles and the eyes of a robot;brain ultrasound; environmental biosensors.
METHOD: Each key photonic I/O components – such as a ring modulator, photodetector and a vertical grating coupler – serves to control and guide the light waves on the chip, but the design had to conform to the constraints of a process originally thought to be hostile to photonic components. To enable light to move through the chip with minimal loss, the researchers used the silicon body of the transistor as a waveguide for the light. They did this by using available masks in the fabrication process to manipulate doping, the process used to form different parts of transistors.
After getting the light onto the chip, the researchers needed to find a way to control it so that it can carry bits of data. They designed a silicon ring with p-n doped junction spokes next to the silicon waveguide to enable fast and low-energy modulation of light. Using the silicon-germanium parts of a modern transistor – an existing part of the semiconductor manufacturing process – to build a photodetector took advantage of germanium’s ability to absorb light and convert it into electricity. A vertical grating coupler that leverages existing poly-silicon and silicon layers in innovative ways was used to connect the chip to the external world, directing the light in the waveguide up and off the chip. The researchers integrated electronic components tightly with these photonic devices to enable stable operation in a hostile chip environment.
It will not be difficult to optimize the components to further improve their chip’s performance.
http://phys.org/news/2015-12-demo-processor-ultrafast.htmljCp
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