Is this glass square the long, long future of data storage?

Scientists at Microsoft Research in the United States have demonstrated a system called Silica for writing and reading information in ordinary pieces of glass which can store two million books’ worth of data in a thin, palm-sized square.

In a paper published today in Nature, the researchers say their tests suggest the data will be readable for more than 10,000 years.

What tiny pulses of light can do

The new system, called Silica, uses extremely short flashes of laser light to inscribe bits of information into a block of ordinary glass.

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).

These attosecond bursts can be used to observe the motion of electrons inside atoms and molecules – and in 2023 the Nobel Prize in Physics was awarded for pioneering work in this area, to Ferenc Krausz (coincidentally my former PhD supervisor), Anne L’Huillier and Pierre Agostini.

Writing in glass

Femtosecond laser pulses also have a practical technological application. They can be used to make changes deep inside transparent materials such as glass.

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 metre to a side, is affected. This is called a “voxel”, which can be made at precisely controlled positions in the glass.

Decades of research

The idea of using laser-written voxels for three-dimensional data storage is not new.

Eric Mazur and co-workers at Harvard University in the US investigated volumetric optical storage back in the 1990s. Their groundbreaking work demonstrated that permanent data structures could be inscribed into common glass using femtosecond lasers.

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 commercialise 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.

A complete system

The Silica project does not claim to have made a new scientific breakthrough. Instead the team presents the first comprehensive demonstration of a practical real-world technology.

Their work brings together all the key elements of such a storage platform based on femtosecond lasers and glass. It includes encoding data, writing, reading, decoding and error correction. The work explores different strategies for reliability, writing speed, energy efficiency and data density, and involves systematic assessments of the data lifetime.