PhysOrg looks through a Microsoft Research Labs breakthrough called Silica that can use pulses of laser light to inscribe ordinary glass blocks so that they’ll work as a data-storage medium with the capacity to last thousands of years:
These pulses are called “ultrashort” for a reason. Each one lasts mere quadrillionths of a second (aka femtoseconds or 10–15 s).
To get your head around that: comparing ten femtoseconds to a single minute is like comparing one minute to the entire age of the universe.
These incredibly short flashes can be used to generate even shorter bursts of light lasting attoseconds (a thousandth of a femtosecond or 10–18 s).
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These lasers produce light of a wavelength that normally passes through glass without interaction. However, when ultrashort pulses of this light are tightly focused on a particular region, it produces an intense electric field that alters the molecular structure of the glass in the focal zone.
This means only a tiny three-dimensional volume, often less than a millionth of a meter to a side, is affected. This is called a “voxel,” which can be made at precisely controlled positions in the glass.
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In 2014, Peter Kazansky and colleagues at the University of Southampton in the UK reported data storage in fused quartz glass with a “seemingly unlimited lifetime.” This helped to to establish the idea of ultra-stable glass-based memory devices.
In 2024, Kazansky spun out a company called SPhotonix to commercialize what they describe as “5D glass nanostructuring.” Their vision of a “5D memory crystal” even made its way into popular culture: a similar device appeared in the latest Mission Impossible film, The Final Reckoning, portrayed as a secure vault capable of containing a powerful but sinister AI.
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Silica looked at two main types of laser-written voxels.
The first consists of tiny elongated void-like features created by laser-driven “micro-explosions” inside the glass. These allow an extremely high storage density of 1.59 gigabits per cubic millimeter.
The second type involves making subtle changes in the local refractive index of the glass. These can be written faster, using less energy—but each cubic millimeter of glass can hold less data. This method can write about 65.9 megabits per second, and the authors say this could be increased with more laser beams.
Finally, accelerated aging experiments suggest that the written data, even in the case of the more sensitive phase voxels, could remain stable for more than 10,000 years. This vastly exceeds the lifetime of conventional archival storage media such as magnetic tape or hard drives.
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You can read more of the Silica voxel research here, in Nature.