Optical disc

5D optical disc could store 500TB for billions of years

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Hard drives and flash storage have become more reliable over the years, but only on a human timescale. What if we needed data storage that lasted longer? Decades? Millennia? Key to this vision could be 5D optical storage, which has a data density 10,000 times that of a Blu-ray disc. But writing data to glass plates like this has always been way too slow until now. A new technique developed at the University of Southampton dramatically speeds up the process, without affecting the reliability of the data.

This type of data storage uses three layers of nanoscale dots in a glass disc. The size, orientation, and position (in three dimensions) of the points give you the five “dimensions” used to encode the data. Researchers say a 5D disc could still be readable after 13.8 billion years, but it would be surprising if someone was there to read it at that time. In the shorter term, 5D optical media could also survive after being heated to 1,000 degrees Celsius. You can see an older, smaller version of the disc above.

This is not the first time that 5G optical data storage has emerged. It was just unbelievably slow before. Data is added to the discs with lasers, but if the laser travels too fast, the structural integrity of the disc is compromised. The technique devised by doctoral student Yuhao Lei uses a femtosecond laser with a high repetition rate. The process begins with a seeding pulse which creates a nanovid, but the fast pulse does not need to write any data. The repeated weak pulses exploit a phenomenon known as near-field enhancement to sculpt nanostructures in a smoother way.

The researchers evaluated the laser pulses at various power levels, finding a level that accelerated writing without damaging the silica glass disc. The study reported a maximum data rate of one million voxels per second, but each bit requires multiple voxels in 5D optical systems. This corresponds to a data rate of approximately 230 kilobytes per second. At this point, it becomes possible to fill one of the disks, which have an estimated capacity of 500TB. It would take about two months to write so much data, after which it cannot be changed.

This work is still in its early stages, but the team managed to write and recover 5GB of text data using 5D optical media. All you need to read the stored data is a microscope and a polarizer, and it should be readable for eons. We might not have anything interesting enough to save for a few billion years, but maybe someday we will.

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