Scientists store data for a long time with light

Researchers have succeeded in stably storing data on a memory chip using light. It was also possible to read the data again with light. The material used to store the data is not new and is also used in rewritable CDs and DVDs.

The materials scientists from the universities of Oxford and Münster, among others, managed to develop a stable memory that can be described by means of light pulses. It is also possible to both write and read the memory with one light pulse. The material used, which can also be found in other rewritable media, such as DVDs and CDs, is Ge2Sb2Te5, or gst. The material can be brought into two different states with the aid of light, a ‘formless’ state or into a neat crystal lattice.

To do the latter, the researchers developed a system in which a small patch of gst is placed on top of a silicon nitride strip. The strip functions as a waveguide to carry the light. By sending a powerful pulse of light through the waveguide, the state of the gst can be changed. In fact, it melts very quickly, after which it loses its crystal structure. A slightly less strong light pulse can then cause the material to change again into a crystal structure at the relevant location and vice versa. If the gst is left alone, the condition does not change.

Later, the memory can be read again by sending less powerful light pulses to it via the waveguide. The difference in state, a crystal lattice or a formless state, is the difference between a 1 or a 0. By simultaneously sending different wavelengths of light through the waveguide, which is also called wavelength multiplexing, it is possible to read and describe with a single pulse of light.

The researchers also discovered that it is possible to form different mixtures of formless and crystal structures in the material in quick succession with the different intensities of the light pulses. When pulses of lower intensity were then sent through the waveguide, the minute differences between the emitted light could be observed. With this, eight different states could be read or written, which makes it possible to do more than just read a 0 or a 1. A single memory bit can therefore be brought into eight different read and write states, with which it should be possible to perform calculations. to do on memory.

According to one of the researchers, the optical bits can be written with frequencies of 1GHz, which can lead to much faster data storage. The team is now investigating how the technology can be made useful, with an electrical-optical connection high on the list.

The research is described in detail in Nature Photonics.