The world’s first entirely light-based memory chip to store data permanently has been developed by material scientists. The device, which makes use of materials used in CDs and DVDs, could help dramatically improve the speed of modern computing.
Today’s computers are held back by the relatively slow transmission of electronic data 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,’ explains Professor Harish Bhaskaran, who led the research. ‘But we think using light can significantly speed this up.’
Simply bridging the processor-memory gap with photons isn’t efficient, though, because of the need to convert them back into electronic signals at each end. Instead, memory and processing capabilities would need be light-based too. Researchers have tried to create this kind of photonic memory before, but the results have always been volatile, requiring power in order to store data. For many applications — such as computer disk drives — it’s essential to be able to store data indefinitely, with or without power.
Now, an international team of researchers including researchers from Oxford University’s Department of Materials has produced the world’s first all-photonic nonvolatile memory chip. The new device uses the phase-change material Ge2Sb2Te5 (GST) — the same as that used in rewritable CDs and DVDs — to store data. This material can be made to assume an amorphous state, like glass, or a crystalline state, like a metal, by using either electrical or optical pulses. In a paper published in Nature Photonics, the researchers describe the device they’ve created, which uses a small section of GST on top of a silicon nitride ridge, known as a waveguide, to carry light.
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