By: Steve Bush November 2, 2021
The University of Southampton stores data on glass, the density of which can compress 500 TB of data onto a CD-sized substrate.
Using three spatial dimensions, data is written in miniature shapes through a large piece of quartz glass. These shapes have two independent optical properties-two additional dimensions-forming the so-called five-dimensional ('5d') data storage. The Southampton team can write 1,000,000 voxels per second, which is equivalent to ~230kbyte/s.
They used it to record 6 Gbytes, four squares of 8.8 x 8.8 mm each on a quartz glass substrate, and to draw the university logo (see picture). The reading accuracy is close to 100%.
"The physical mechanism we use is universal," said researcher Lei Yuhao. "Therefore, we expect that this writing method can also be used for fast nanostructures of transparent materials for applications in 3D integrated optics and microfluidics."
The shape described as "nano flakes" is approximately 500 x 50 nanometers. "Nano-flaky nanostructure means that there is a nano-void in the center and two short nano-cracks perpendicular to the laser polarization direction," Lei told Electronic Weekly.
These cracks face each other around the gap and can be written in different directions to encode data.
Lei explained that these structures produce birefringence in glass, which is characterized by two parameters:
In the recording process, the slow axis direction and the retardation intensity are controlled by the polarization and intensity of the light, respectively.
Together, these are used to encode 4-bit data into each structure, and they are written in pairs to obtain 8-bits, allowing the text to be encoded as ASCII.
For fast writing, a high repetition laser is used. But they cannot be used directly, because the total power will locally overheat the substrate.
"We managed to reduce thermal damage through effective energy deposition with near-field enhancement, which is a phenomenon in which the optical field near the nanostructures defined by the polarization direction increases," Lei said. "More specifically: the isotropic nanovoids were originally created with pulse energy higher than the quartz glass micro-explosion threshold. With a small number of laser pulses with subsequent energy reduction, it is elongated into anisotropically through near-field enhancement The nano flake-like structure eliminates the harmful thermal effects of femtosecond pulses at the megahertz rate."
According to Lei, this method increases the data writing speed to a practical level: "We can write tens of gigabytes of data in a reasonable time."
This work is covered by Optica (formerly OSA) published on Optica, "Controlling high-speed ultrafast laser anisotropic nanostructures through near-field enhancement controlled energy deposition." You can read the full text without paying.
Although this method can write 500Tbytes of data into a CD-sized patch, it will take a while: "With an upgrade that allows parallel writing, the researchers stated that it should be feasible to write such a large amount of data in about 60 days. "According to Optics.
Image credit: Yuhao Lei and Peter G. Kazansky, University of Southampton
Tagged as: Computer Memory Glass Laser Storage University of Southampton
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