Researchers create first permanent photonic memory chips

Science : Using photons instead of electrons in computer chips is a long-standing area of research because photons move quicker than electrons and don’t generate as much heat. However, photonic devices have their own drawbacks, with one of the most significant being that their memory circuits only store information while they are powered on. Now Harish Bhaskaran of the University of Oxford in the UK and Wolfram Pernice of the Karlsruhe Institute of Technology in Germany have created a photonic data storage system that uses GST—an alloy of germanium, antimony, and tellurium—which is also used in rewritable CDs and DVDs. When hit with intense laser light, GST changes structure from an ordered crystalline lattice to an unordered, amorphous one. CD and DVD drives use a low-intensity laser to read data by detecting the different ways GST’s two structures reflect the light. Bhaskaran and Pernice noticed that the two structures also differ in how much of the light they absorb. The researchers placed a layer of GST over a structure called a waveguide, which contains and channels pulses of light. Using the waveguide, they could change and then read the GST’s structure at specific locations and could even read and write at multiple locations simultaneously, something that can’t be done with electronic data storage. They were also able to adjust how much of the material changed structure at each location, so that they could store data in up to eight different combinations as opposed to the standard binary.