Hitachi has developed a method of writing and reading digital information on slivers of quartz glass, offering a reliable way to safely store data, almost for ever.

Hitachi's new technology uses a laser to store data in binary form by creating dots inside a thin sheet of quartz glass, which can be read with an ordinary optical microscope. Data can be stored in many layers inside the quartz glass, by changing the focus point of the laser - a technique also met in multi-layered recordable optical discs.

The laser used for data recording is emitting ultrashort pulses of light, electromagnetic pulses whose time duration is of the order of a femtosecond. Hitachi has also developed a recording technology that uses a spatial phase modulator, which modulates both the phase and the amplitude of the laser beam. This results to a higher recording of up to 100 dots at a time, Hitachi said.

Reading of the stored data is achieved by using an ordinary optical microscope. By applying signal processing techniques to the read-out signal, Hitachi's researchers have achieved an error-free reading with a reproduction SNR of just 15dB.

The prototype storage device is two centimetres square and just two millimetres thick. It is resistant to many chemicals and unaffected by radio waves, can be exposed directly to high temperature flames and heated to 1,000 degrees Celsius for at least two hours without being damaged. It is also waterproof, meaning it could eventually store data for hundrends of years.

The material currently has four layers of dots, which can hold 40 MB per square inch, approximately the density on a music CD (35MB). More layers can be also added to future prototypes.

Hitachi have not decided when to put the chip to practical use.

The company will present a related paper at this year's International Symposium on Optical Memory (ISOM2012,) which willbe held in Tokyo, Japan, in September 30, 2012.