5D optical data storage

5D optical data storage (sometimes known as Superman memory crystal[1]) is a nanostructured glass for permanently recording 5-D digital data[2] using femtosecond laser writing process.[3] The memory crystal is capable of storing up to 360 terabytes worth of data[4][5] for billions of years.[6][7][8][9] The concept was experimentally demonstrated in 2013.[10][11][12] As of 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 placed aboard the Tesla Roadster in space.[13]

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.[1][14][15] 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.[1]

Up to 18 layers have been tested using optimized parameters with a light pulse energy of 0.2 μJ, a duration of 600 fs and a repetition rate of 500 kHz. Assuming 100% efficient laser that is 1W power consumption for (at most) 0,5 Mbit/sec data rate. For a data rate of 100MBytes/s that adds up to 1,6kW. Testing the durability using accelerated aging measurements shows that the decay time of the nanogratings is 3×1020±1 years at room temperature (30 °C). At an elevated temperature of 189 °C the extrapolated decay time is comparable to the age of the Universe (13.8×109 years). By recording data with a numerical aperture objective of 1.4 NA and a wavelength of 250–350 nm, a capacity of 360 TBytes can be achieved.[1]

The format has a unique 5-dimensional method of storing data, according to the University of Southampton:

It can be read with a combination of an optical microscope and a polarizer.[17]

The technique was first demonstrated in 2010 by Kazuyuki Hirao's laboratory at the Kyoto University.[18] Further, the technology was developed by Peter Kazansky's research group at the Optoelectronics Research Centre, University of Southampton. [19][20][21][22]