Hitachi targets quartz glass for long-term storage

September 25, 2012 // 12:07 p.m.

Tags: #femtosecond-laser #hitachi #kiyotaka-miura #kyoto-university #optical-storage #quartz-glass #storage

Hitachi's storage arm has developed a novel technique for recording data directly onto glass, in a move that could dramatically increase storage capacities while producing write-once, read-many (WORM) media significantly more robust than today's recordable CDs, DVDs and Blu-rays.

Existing in prototype form, the storage system uses dots captured in layers of quartz glass to store data. These binary dots are read back using an optical microscope in a procedure not a million miles away from how optical discs are read today.

Where the technology differs is in its longevity: as it doesn't rely on any dyes, the data should survive almost indefinitely. Designed as a semi-permanent storage medium, the technology uses the inherent strength of quartz glass and its resistance to heat, magnetism and water to produce something that should last forever - so long as nobody breaks the glass.

The medium itself consists of four layers of quartz glass, which is irradiated by a pulsed femotosecond laser to form areas with different refractive indices. These areas form the dots, and their different reaction to light when read gives the system the ability to store 0s and 1s for binary data. So far, so very-fragile-optical-disc. Recording a hundred dots at a time, through a modulator capable of adjusting the amplitude and phase of the laser light, the system promises improved recording speeds - but it's the capacity that is most impressive.

Despite being a very early prototype, based on work done by Hitachi in 2009 on laser tomography storage, the prototype created by Professor Kiyotaka Miura of the Kyoto University is impressively capacious: measuring just 2cm on a side and a mere 2mm thick, the square of glass holds data at a recording density of 40MB/inch² - an increase over a CD-R's density of 35MB/inch², with significantly improved archival capabilities.

Just how robust is the prototype? According to Miura, impressively so: during testing, the prototype was heated for two hours at 1000℃ - a handy way of quickly figuring out what a few years of more normal temperatures might do - with no loss of data. 'This corresponds to a retention period of more than a few hundred million years,' Miura claims.

While Miura states that Hitach will be developing the technology for exploitation, no date has yet been given for the release of a commercial implementation. Meanwhile, Miura is due to present his findings at the International Symposium on Optical Memory later this month.

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