Memory Chip: Using Light to Make a Permanent Memory Chip?

A light-based memory chip that stores data permanently is a new development from University of Oxford and other scientists at the universities of Karlsruhe, Munster and Exeter. Taking materials already used in CDs and DVDs, the researchers say this chip is likely to significantly ramp up the speed of our modern computing, as this release noted.

As it is, computers now slow down to allow for electronic data to move between the processor and the memory. "There's no point using faster processors if the limiting factor is the shuttling of information to-and-from the memory -- the so-called von-Neumann bottleneck," said Professor Harish Bhaskaran, the research leader, in the release. "But we think using light can significantly speed this up."

It isn't enough to link the processor and memory with photons, though--they'd still need to be switched back to electronic signals at each end of the process. So, processing and memory capabilities need to be light-based, as the researchers noted.

While this has been tried before, the recent team say they have for the first time developed a system that is non-volatile and is able to store data indefinitely. That is, the new product is entirely composed of photons.
It uses the material Ge2Sb2Te5, which is the thing that is also within CDs and DVDs, to store data-because of its ability to take other shapes, like glass, or to achieve a crystalline condition, like metal-through either electrical or optical pulses. The above is also known as GST, or an alloy of germanium-antimony-tellurium that allows for phase changing, said the release.

The scientists published their findings recently in Nature Photonics, noting that they layered GST atop a ridge of silicon nitride, in order to carry light.
When light is intensely pulsed through the waveguide, the GST changes form. It can melt and then cool to reach an amorphous structure; a less fierce pulse can move it to a crystalline condition. The amount of light that later goes through the waveguide is affected by its relative state.

Through these methods, the team was also able to use one pulse to write and read to memory at the same time. "In theory, that means we could read and write to thousands of bits at once, providing virtually unlimited bandwidth," said Professor Wolfram Pernice, University of Munster, in the release.

The researchers are now at work on making use of this new technology. They hope to put together a new kind of interconnection that is electrical and optical, to allow memory chips to interface with other things with the use of light, not electrical signals, confirmed the release.

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