Photonic memory device breakthrough

Created January 16, 2019
Applications and Research

Eindhoven researchers develop hybrid data storage technology with advantages of both light and magnetic hard drives

Researchers at the Institute of Photonic Integration of the Eindhoven University of Technology (TU/e) have developed a ‘hybrid technology’ which promises the advantages of both light and magnetic hard drives. In the research, use of ultra-short (femtosecond) light pulses allowed data to be directly written in a magnetic memory in a fast and highly energy-efficient way. Moreover, as soon as the information is written (and stored), it moves forward leaving space for empty memory domains to be filled in with new data. This research, published in Nature Communications, promises to revolutionise the process of data storage in future photonic integrated circuits.

The researchers note that data in datacentres, for example, are stored in hard drives in the form of ‘bits’, tiny magnetic domains with a north and a south pole. The direction of these poles (‘magnetisation’), determines whether the bits contain a digital 0 or a 1. Writing the data is achieved by ‘switching’ the direction of the magnetisation of the associated bits.

Conventionally, switching occurs when an external magnetic field is applied, which would force the direction of the poles either up (1) or down (0). Alternatively, switching can be achieved via the application of a femtosecond laser pulse. This form of all-optical switching results in a more efficient and much faster storage of data.

“All-optical switching for data storage has been known for about a decade. When all-optical switching was first observed in ferromagnetic materials – amongst the most promising materials for magnetic memory devices – this research field gained a great boost,” states Mark Lalieu, PhD candidate at the Applied Physics Department of TU/e. However, the switching of the magnetisation in these materials requires multiple laser pulses and, thus, long data writing times.

Lalieu, under the guidance of Reinoud Lavrijsen and Bert Koopmans, was able to achieve all-optical switching in synthetic ferrimagnets – a material system highly suitable for spintronic data applications – using single femtosecond laser pulses, thus exploiting the high velocity of data writing and reduced energy consumption.

So how does all-optical switching compare to modern magnetic storage technologies? “The switching of the magnetisation direction using the single-pulse all-optical switching is in the order of picoseconds, which is about a 100 to 1,000 times faster than what is possible with today’s technology,” reports Lalieu. “Moreover, as the optical information is stored in magnetic bits without the need of energy-costly electronics, it holds enormous potential for future use in photonic integrated circuits.”

The TU/e research was performed on micrometric wires. In the future, smaller devices on the nanometer scale should be designed for better integration on chips. In addition, working towards the final integration of the photonic memory device, the Physics of Nanostructure group is currently also busy investigating the read-out of the (magnetic) data, which can be achieved all-optically as well.

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This article was written
by John Williamson

John Williamson is a freelance telecommunications, IT and military communications journalist. He has also written for national and international media, and been a telecoms advisor to the World Bank.