Transparent data for eternity
© University of Southampton
December 2021

Transparent data for eternity

By Christoph Brix
Constantly increasing speed, consistently growing volumes: Our digitized world is made up of humongous amounts of data. Researchers have developed a new high-speed method of storing huge information volumes on crystal 5D discs for billions of years.

The key performance data targeted by the technology that has been developed at the University of Southampton are impressive: A 5D fused quartz data storage disc suitable for femtosecond laser writing (see info element) is supposed to be able to store up to 500 terabytes of data in a space equal to that of a CD – which would equate to 10,000 times the data density of a Blu-ray disc.

About femtosecond lasers
Transparent data for eternity© unsplash

Femtosecond lasers are infrared lasers with very weak, short light pulses in the range of femtoseconds. Femto is a unit prefix. One femtosecond (1 fs) equates to 10–15 seconds. Among other things, these lasers are used in a wide range of medical applications such as dental medicine, ophthalmology (cataract surgery) and cancer therapy.

To illustrate the point: Storing the information contained in all of the 39 million books held by the U.S. Library of Congress in Washington, D.C. on shelves with a length of about 838 miles (1,349 kilometers) would occupy around 20 terabytes. A digital library of the written pages from all the books in the world has a size of some 400 terabytes – and would therefore fit on a single one of these new wonder discs. Or, instead of written documents, 125,000 movies could be stored on such a CD-size 5D storage disc with 500 terabytes. The current record stands at 360 terabytes.

The long life of the data is another advantage of this novel storage device. The scientists estimate that the information stored at room temperature would still be retrievable after 13.8 billion years. By contrast, a Blu-ray disc has a maximum estimated life span of 80 years. The fused quartz storage systems are supposed to be able to withstand short-term exposure even to temperatures of around 1,000 degrees centigrade (1,832 degrees Fahrenheit), which makes them perfectly suited for eternity. “While cloud-based systems are designed more for temporary data, we believe that 5D data storage in glass could be useful for longer-term data storage for national archives, museum, libraries or private organizations,” says Yuhao Lei from the University of Southampton.

Timeline of data storage history
  • 20000 BC
    Hunters capture their quarry in the Lascaux cave paintings.
  • 3000 BC
    In Mesopotamia, cuneiform messages are chiseled into stone tablets.
  • 1377
    The first book, titled “Jikji” and covering Buddhist topics, is printed in China.
  • 1450
    In Mainz, Johannes von Gutenberg, invents modern book-printing using movable type.
  • 1884
    American entrepreneur Herman Hollerith files his first patent application for the punched card, representing a data revolution at the time. Its storage capacity is 0.08 KB
  • 1937
    Konrad Zuse uses punched cards for his first freely programmable computer “Zuse Z1.
  • 1951
    Magnetic tapes can process clearly larger data volumes. The plastic tape coated with a magnetic material is able to store the information of some 10,000 punched cards. Even so, its capacity of 800 KB seems tiny from today’s perspective.
  • 1969
    IBM causes a sensation with the first 8-inch floppy disc boasting 80 KB of storage capacity, which later grows to 1,000 KB.
  • 1970
    Klaas Compaan and Piet Kramer from Philips develop the first “glass disc” that can be read only with a laser. This prevents direct contact with the disc and losses due to abrasion.
  • 1977
    Commodore launches its Datasette as an affordable storage device for its 8-bit home computer C64, with a storage capacity of 100 Kbytes per 30 minutes of tape runtime.
  • 1982
    The first audio CD, a recording of ABBA’s “The Visitors” album, hits the market. Theoretically, the CD stores 74 minutes of music – the duration of Beethoven’s 9th Symphony.
  • 1988
    Digipro, a small PC manufacturer, presents the first solid state drive (SSD) with a 16-MB flash memory.
  • 1989
    The CD-ROM with its 650 to 700 MB celebrates its rollout as an information storage device.
  • 1996
    Israeli engineer Dov Moran presents the first USB flash drive, a pocket-size 5-MB memory.
  • 2001
    The first SD SanDisc memory card has an 8-MB memory.
  • 2001
    The DVD with up to 18 GB begins to fiercely compete with the CD.
  • 2006
    In the war of formats, the Blu-ray disc wins against its competitors, HD DVD and VMD. It features a storage capacity of up to 50 GB.
  • 2016
    The Ultra HD Blu-ray can store up to 128 GB of data on four storage layers.
Optimization of existing technology

5D optical data storage in transparent materials per se is not a novelty. In 1996, initial ideas emerged of burning data onto transparent materials using ultrafast lasers. However, it took 17 years to accomplish the leap from theory into practice: in 2013, the scientists in Southampton presented the first prototype of a transparent storage system with data points having been laser-engraved into its structure.

Crystal storage as a Hollywood vision

Don’t be surprised if glass or crystals as data storage devices seem familiar to you – HAL 9000, the computer on board of the Discovery One spaceship featured in the epic Academy Awards winning science fiction movie “2001: A Space Odyssey,” had such a crystal memory, a vision that Stanley Kubrick had as far back as in 1968. And he wasn’t the only one: in the first Superman movie released in 1978, the entire memory of the planet Krypton had been committed to a crystal storage device. So, preserving this classic movie on a crystal disc suggested itself. Microsoft did so in 2019 in its “Silica” project (pictured below).

Transparent data for eternity

The advantage of the glass storage discs is remarkable: The engraved data points are tiny nanograting units. These complex structures feature the three commonly known spatial dimensions (length, width, height) and additionally generate two optical dimensions splitting the incident light (double refraction). While the orientation of the light defines the fourth dimension, the retardance caused in the process defines the fifth. That’s why researchers refer to the technology as 5D data storage. Sounds – and is indeed – complicated, but the crucial part is that the interaction of the light enables clearly more information to be stored and read. The data density increases to eight bits per nanograting, not least because the data points with a mere size of 500 by 50 nanometers can be read out from various directions, using a combination of a light microscope and a polarizer, which essentially is nothing but a sunglass lens with a polarizer.

Writing at higher speed

The laser writing technology used in 2013 still had a huge flaw because the data transmission speed was extremely slow. But now the researchers have given the process a boost: by means of an enhanced writing method using laser pulses of varying intensities the nanograting structures are burned into the silica glass disc with both greater energetic efficiency and at much higher speed. “This new approach improves the data writing speed to a practical level, so we can write tens of gigabytes of data in a reasonable time,” says Lei. Furthermore, thermal damage to the grating structure, which kept occurring with the previously used burning method, can be avoided by the ultrashort light pulses.

The UK researchers have managed to write text data onto silica glass discs with nearly 100-percent readout accuracy at a high rate of up to 1,000,000 voxels per second – equating to a data volume of 230 kilobytes or more than 100 pages of text per second.

This new storage technology has been causing a sensation not only on Earth. In 2018, US billionaire and SpaceX owner Elon Musk launched a Tesla Roadster into space aboard a Falcon Heavy rocket for PR purposes. The car had a 5D data storage disc on board with the entire Foundation trilogy – the popular science fiction series by the Russian writer and inventor of the Three Laws of Robotics Isaac Asimov.