Microsoft Researchers Blast Glass with Lasers to Encode Terabytes of Data for Millennia

A Microsoft research team has published a paper detailing the latest in Project Silica — an effort to create data storage that will last for millennia, by encoding data in glass as "phase voxels."

"Long-term preservation of digital information has long challenged archivists and datacenters, as magnetic tapes and hard drives degrade within decades," says Microsoft's Richard Black of the problem the team set out to solve. "Existing archival storage solutions have limited media lifespans that make them less than ideal for preserving information for future generations. Now, we are excited to report significant progress on Project Silica (opens in new tab), our effort to encode data in glass using femtosecond lasers, a technology that could preserve information for 10,000 years."

The idea of storing data optically, rather than magnetically or as electronic charges, isn't new: while not the first, Compact Discs (CDs) are by far the most well-known and gave rise to higher-density formats like Digital Versatile Disc (DVD) and Blu-ray. All three are not only readable using a low-power laser, but writable: special dyes in writable discs change state when excited by a slightly-higher-power laser, allowing data to be written for later reading.

CDs, DVDs, and Blu-rays are not a "forever medium," however. They degrade over time, in some instances with manufacturing defects or poor-quality dyes in a matter of years, and even archival-grade versions like Millenniata's M-DISC are expected to degrade after around a hundred, years even when stored in ideal environments like the dry inside of a salt mine.

Project Silica is different: a considerably higher-power laser than you'd find in commercial optical disc writers is used to encode data into glass, which stands up to the elements considerably better than the plastics used for traditional optical discs. Where previous work had used high-priced fused silica glass, Microsoft's latest paper describes using the same core approach to encode data in borosilicate glass — the high-temperature low-cost glass used in traditional Pyrex cookware.

"This advance addresses key barriers to commercialization: cost and availability of storage media," Black claims of the work. "We have unlocked the science for parallel high-speed writing and developed a technique to permit accelerated aging tests on the written glass, suggesting that the data should remain intact for at least 10,000 years. The new technique stores hundreds of layers of data in glass only 2mm thin, as with previous methods, but with important improvements. The reader for the glass now needs only one camera, not three or four, reducing cost and size. In addition, the writing devices require fewer parts, making them easier to manufacture and calibrate, and enabling them to encode data more quickly."

Data is encoded in the glass using femotosecond laser pulses, creating "phase voxels" that can be read back by camera. While the process is faster than previous efforts, it's still relatively slow compared to modern storage media: a single beam can write at a claimed 25.6Mb/s (3.2MB/s), though multiple beams can write in parallel to improve overall throughput. In testing, the researchers say, the team managed to write 4.8TB of readable data to a 120mm-square 2mm-thick piece of glass, using a total of 301 layers, and with an estimated lifetime "exceeding 10,000 years."

The team's work has been published in the journal Nature under open-access terms; Black claims that "the research phase is now complete," but stops short of promising to bring the technology to production.