5D optical data storage
5D optical data storage (sometimes known as Superman memory crystal) is a nanostructured glass for permanently recording digital data using a femtosecond laser writing process. The memory crystal is capable of storing up to  worth of data for billions of years. The concept was experimentally demonstrated in 2013. Hitachi and Microsoft have researched and developed 5D optical storage techniques.

The five dimensions consist of the size, orientation and the three-dimensional position of the nanostructures.

Technical design 
The concept is the bulk storing of data optically in non-photosensitive transparent materials such as fused quartz, which is renowned for its high chemical stability and resistance. Writing into it using a femtosecond-laser was first proposed and demonstrated in 1996. The storage media consists of fused quartz where the spatial dimensions, intensity, polarization, and wavelength is used to modulate data. By introducing gold or silver nanoparticles embedded in the material, their plasmonic properties can be exploited.

Up to 18 layers have been tested using optimized parameters with a light pulse energy of , a duration of 600 fs, and a repetition rate of 500 kHz. Assuming a 100% efficient laser, that is  of energy consumption for a maximum 0.5 Mbits of data storage.  For 1000 Mbits of storage that adds up to .  Testing the durability using accelerated aging measurements shows that the decay time of the nanogratings is 3×1020±1 years at room temperature, . At an elevated temperature of , the extrapolated decay time is comparable to the age of the Universe ().  By recording data with a numerical aperture objective of 1.4 NA and a wavelength of , a capacity of 360 terabytes can be achieved.

The format has a novel method of storing data called "5-dimensional". This is more for marketing purposes since the device has 3 physical dimensions and no exotic higher dimensional properties. The fractal/holographic nature of its data storage is also purely 3-dimensional. According to the University of Southampton:

It can be read with a combination of an optical microscope and a polarizer.

The technique was first demonstrated in 2010 by Kazuyuki Hirao's laboratory at the Kyoto University. Further, the technology was developed by Peter Kazansky's research group at the Optoelectronics Research Centre, University of Southampton.

Uses 

Since 2018 the technology is in production use by the Arch Mission Foundation. Its first and second discs were given to Elon Musk: one disc is in his personal library, and the other was placed aboard the Tesla Roadster in space.

GitHub, a subsidiary of Microsoft, plans to use this technology to archive all public Git repositories. Microsoft refers to this technology as Project Silica with a claimed lifetime of over 10,000 years.

See also 
 3D optical data storage
 DNA digital data storage
 Data store

References

External links 
 Official 5D Memory Crystal website

 
Solid-state computer storage media
Non-volatile memory
Digital preservation