The push for faster computers…more powerful computers however that is defined…proceeds along several lines: Traditional (in silicon semiconductors), quantum (several forms of quantum computing), biological (based on organic chemistry), and optical (using photons of light instead of electrons). Almost every year advances are made along each line of research. Eventually the advances will add up to one or more functional new computer technologies. With effort some may also become commercially successful. Here’s an entry along the optical line of research.
The investigators were looking for an understanding of optical switching leading to an all optical micro-transistor that could operate inside a photonics chip. This has been for some time a high priority of optical computing research. As the key piece of their research, they used photonic crystals, dielectric nanostructures that selectively block photons of light at certain wavelengths in a way similar to what semiconductor crystals do to electrons. What they discovered was a way of creating areas of near-vacuum inside photonic crystals. Inside the vacuum were quantum dots (nanoscale crystals) that could be excited – brought to a higher state of energy, in this case by photons – by a color-coded pulse of laser light in as little as one-trillionth of a second. The quantum dots, in excited or non-excited state, could in turn control the flow of other laser pulses – in short, switching. As with traditional semiconductors, this type of ‘switching’ can be used for computer logic (digital gates).
University of Toronto quantum optics researchers Sajeev John and Xun Ma have discovered new behaviours of light within photonic crystals that could lead to faster optical information processing and compact computers that don’t overheat.
“We discovered that by sculpting a unique artificial vacuum inside a photonic crystal, we can completely control the electronic state of artificial atoms within the vacuum,” says Ma, a PhD student under John’s supervision and lead author of a study published in a recent issue of Physical Review Letters. “This discovery can enable photonic computers that are more than a hundred times faster than their electronic counterparts, without heat dissipation issues and other bottlenecks currently faced by electronic computing.”
“This new mechanism enables micrometer scale integrated all-optical transistors to perform logic operations over multiple frequency channels in trillionths of a second at microwatt power levels, which are about one millionth of the power required by a household light bulb,” says John. “That this mechanism allows for computing over many wavelengths as opposed to electronic circuits which use only one channel, would significantly surpass the performance of current day electronic transistors.”
[Source: Nanotechnology Today]
The principles behind optical computing are reasonably well understood. Much of the difficulty in creating optical computing has been more on the practical end. Photonic crystals are difficult to manufacture. Whether there will be similar difficulties in manufacturing photonic crystals with vacuum spaces remains to be seen. In any case, the road to development of a photonic computer may go through this research. There are big advantages – especially in the superfast switching allowed by using laser control.