New breakthrough allows light to be compressed much more readily
Looking to the future, optical computing is one of several technologies being considered as a high-speed replacement to traditional electrical-based computing. While quantum computing is considered by many as the ultimate future of computing, optical computing is more realizable in the near future.
In fact, optical computing components have already been realized with fiber optic services available in select parts of the country for high speed computing. However, more exotic devices like light-based storage or light transistor-composed CPUs, necessary to build a full optical computer, remain in the really of conjecture.
An important breakthrough in optical computing may help to change that. Researchers at the University of California Berkley have developed a novel method to squeeze light into extremely small spaces, an important hurdle that optical computing faced. Previously researchers could get light to fit in relatively small spaces -- even as small as 200 nm, about 400 times smaller than a human hair. This size helps to dictate the necessary size for the smallest fiber optic fibers, which for various reasons are about five times this width -- or about 1 µm wide.
With the breakthrough, researchers were able to cut light down to fit into spaces a mere 10 nm, 20 times smaller than ever before. The space was a mere five times the width of a single piece of DNA, a size previously thought infeasible to shrink light to. Rupert Oulton, research associate in the group led by mechanical engineering Professor Xiang Zhang, stated of the discovery, "This technique could give us remarkable control over light and that would spell out amazing things for the future in terms of what we could do with that light."
Professor Zhang added, "There has been a lot of interest in scaling down optical devices. It's the holy grail for the future of communications."
Mr. Oulton theorizes that the advance and further compression will yield key breakthroughs due to the properties of electricity and magnetism. In order to achieve an optical computer, you would need at least some electrical components. However the vastly different scales of electricity and light mean that they do not interact neatly or behave in similar ways. He believes by shrinking light to wavelengths similar to that of electrons in computer systems, a plethora of new uses will arise.
The key problem is light doesn't like to fit in spaces that small, normally. While light technically has been squished even farther using a technique called surface plasmonics that bonds photons to electrons, this method in its current state is relatively useless as it only travels a short distance and then the wave dissolves. And traditional waves were constrained to the bulky 200 nm barrier.
After delving into surface photonics research, Mr. Oulton developed a new approach -- a "hybrid" optical system consisting of a very thin semiconductor wire placed in close proximity to a thin, smooth sheet of silver. Normally, light would travel down the center of the wire. But in the new design light travels in the very small gap between the semiconductor and the metal. This yields a light wave with size similar to surface plasmonic waves, but with longevity closer to normal waves. The light waves are able to reach 100 times farther than the most advanced surface plasmonic waves.
The end effect is thanks to the semiconductor/silver combination behaving like a capacitor. As light travels along the gap, it excites electrons, creating a charge on the sheets. This charge in turn helps to feed the light, helping it to travel farther, in an effect similar, but not identical to surface plasmonics. Mr. Oulton was surprised at the simplicity of the design. He stated, "It's really a very simple geometry, and I was surprised that no one had come up with it before."
The approach will offer the best of both worlds in terms of size vs. propagation distance, according to Professor Zhang. He stated, "Previously, if you wanted to transmit light at a smaller scale, you would lose a lot of energy along the path. To retain more energy, you'd have to make the scale bigger. These two things always went against each other. Now, this work shows there is the possibility to gain both of them."
Work does remain in physically implementing the device, but this step should be straightforward. The main reason the team has not yet connected the theoretically modeled devices is that no existing instrumentation can measure light at that small a wavelength. The researchers are looking at exotic ways to detect the new smaller than ever light.
In the end, though, Mr. Oulton believes the research is a giant leap towards the greatest challenge of optical computing -- achieving unity between light and electricity. He stated, "We are pulling optics down to the length scales of electrons. And that means we can potentially do some things we have never done before."
Other researchers on the project included Volker Sorger, Dentcho Genov and David Pile, all part of professor Zhang's group at University of California Berkley.
The project was funded by the U.S. Air Force Office of Scientific Research, the National Science Foundation and the Department of Defense.
DailyTech - Researchers Discover "Holy Grail" of Optical Computing
