Miloš Popović, an assistant professor of electrical, computer and energy engineering, and his team at the University of Colorado Boulder are using photonics, or concentrated light waves, to make more energy-efficient ways for microprocessors to communicate with the memory on microchips that are used in everything from cell phones and computers to PlayStation 3 and Wii video-game consoles.
The goal is to make it possible for companies that produce microprocessors and memory chips to continue offering faster processors with more memory every 18 months, without having to revamp their current chip-manufacturing plants.
Moore’s Law, which was first laid out in 1965, predicted that the size of the transistors used in microprocessors could be shrunk by half about every two years for the same production cost, allowing twice as many transistors to be placed on the same-sized silicon chip. The result? Computer speed that doubles every couple of years.
That projection held true until 2005, Popović said, when it became apparent that the industry couldn’t produce enough power to do it without causing excessive heat, which would melt the chips.
The vast amount of electricity required to flip on and off tiny, densely packed transistors causes excessive heat buildup.
“The transistors will keep shrinking, and they’ll be able to continue giving you more and more computing performance,” Popović said. “But in order to be able to actually take advantage of that, you need to enable energy-efficient communication links.”
Using light waves instead of electrical wires for microprocessor communication functions could eliminate the limitations that are now faced by conventional microprocessors and extend Moore’s Law into the future, he said.
“The most advanced technology makes microprocessor and memory chips. The only way to be relevant was to create photonics technology that can seamlessly live in that fabrication technology without changing it,” Popović said. He and his team were successful in doing that in September.
Now the group is looking at other ways to use photonics to improve electronics, including finding ways to do quantum computing on small chips.
“In some ways, going nanoscale is not just going smaller, it is enabling you to do things you couldn’t do before,” he said.
Funding for the photonics project, which began in 2010 and will end in 2015, comes from the Defense Advanced Research Projects Agency and the National Science Foundation.
Surgical tools and micro-labs
Jeff Squier is a professor in the Department of Physics at the Colorado School of Mines, who has the distinction of holding one of the first Lasik eye-surgery patents and continues to use laser technology to make the next generation of medical diagnostic tools.
He is a pioneer in the area of dimensional focusing, where he uses infrared laser beams, which are considered less damaging to sensitive human tissues, focused through a lens, to create a tremendous amount of power using less energy.
By using this technology, “we can cut much closer to more sensitive membranes than we could ever do before,” Squier said. By using out-of-focus light, where the beam gets bigger, it can be less intense.
“During some surgeries, the out-of-focus light is at a much lower intensity which is so much safer as well. It cuts more precisely, and we expose out-of-focus areas with much less intensity,” he said.
His group also is using femtosecond lasers to produce laboratories on a chip. A femtosecond laser is one that emits short optical pulses. Currently, he is working on using intense light to machine small parts for diagnostic labs on a chip, being produced in CU’s chemical engineering department. The goal is to put everything needed on a chip to be able to analyze blood.
With the femtosecond laser, “we can rapidly prototype and make things out of glass” for the project, he said. Some of the channels needed for the device are about the width of a human hair. The technology has many implications for medical and surgical procedures, he said.
“We’re making the next generation of diagnostic tools. It is a lot of fun. It’s not commercial yet,” Squier said. “We’ve only been at it for two years. The commercialization process takes a while, but people in the industry have taken note and are interested.”
Observations at a nanoscale
The National Science Foundation Engineering Research for Extreme Ultraviolet Science and Technology lab at Colorado State University is developing laser sources that emit in extreme ultraviolet light — significantly shorter wavelengths than visible light — and is a region of the spectrum that is hard to access, said Carmen Menoni, a professor in the Department of Electrical & Computer Engineering at CSU and a principal investigator in the Extreme Ultraviolet lab.
The lab is a collaboration between CSU, CU-Boulder, the University of California Berkeley and the Lawrence Berkeley Lab that was started 10 years ago.
In the past, to produce light at these wavelengths, big, room-sized machines were needed.
“Our approach is to develop lasers that fit on a tabletop,” Menoni said.
The other reason they want to go to these short wavelengths is that they want to make microscopes with a significantly higher resolution.
One of the uses her group has found for lasers that emit in extreme ultraviolet light is microscopes that can see nanoscale structures.
“We’ve also been able to demonstrate that this microscope can actually, by taking flash images, follow dynamic interactions at a nanoscale,” she said.
Menoni and her colleagues also are developing another imaging methodology using extreme UV lasers that can prove composition at the nanoscale.
“There’s very intense activity for extreme UV technology in laser research. We are world leaders in that area,” she said.
Colorado has the largest collection of companies in the country that do optical coatings for lasers. Lasers are used in many areas of science, including particle acceleration and fusion, she said.
“When you go to shorter wavelengths, the interaction of electromagnetic interaction with materials is very different,” she said.
Shorter wavelengths allow scientists to interact with colors, to look at imaging and intensify the contrast in imaging by looking with a specific wavelength. They also allow them to enhance images because certain areas will reflect more or less light than others, she said.
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