Hitachi's fused silica glass storage disk reading process

Hitachi achieves read/write on 100 layer fused silica glass

Hitachi has successfully written and read digital data in 100 layers of fused silica glass – a recording density comparable to a Blu-ray disc.

Fused silica glass offers excellent heat and water resistance making it promising for semi-perpetual data storage of things like historical information and public documents as well personal data that individuals may wish to preserve data for future generations.

Hitachi started developing fused silica storage in 2009 using a process called computed tomography to read data recorded with a femtosecond pulse laser by changing the laser's focal point to form microscopic regions (dots) with differing refractive indices.

But despite success in scaling up the number of layers when nearing the 100-layer level issues arose in dot quality degradation and read errors resulting from crosstalk of data recorded in other layers.

To address these issues Hitachi, in collaboration with Professor MIURA Kiyotaka of the School of Engineering, Kyoto University, used newly developed noise reduction technology to overcome the interference and have now succesfellu read and written data at 100 layers.

In work due to be presented at the 2014 International Symposium on Optical Memory this week, it was verified that with recording layers with a gap of 60μm between layers, 50 layers can be recorded and read on each side of a fused silica disc, giving a total of 100 layers.

The results showed indicated a recording density of 1.5 GB/inch2, comparable to that of a Blu-ray disc, is possible using fused silica glass, and the potential for even greater numbers of layers.

Making use of the 300 million year data storage lifetime found with fused silica glass, a fused silica glass lithograph is set to accompany an upcoming space launch. The fused silica glass lithograph featuring images and a message for 300 million years in the future will be mounted on the “Shin-en 2” miniature payload of the Hayabusa 2 rocket developed by the Kyushu Institute of Technology.

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