Researchers at the University of Southampton have developed a fast laser writing method and energy efficient to produce high-density nanostructures in silica glass. These tiny structures can be used for optical data storage long-term five-dimensional (5D), more than 10.000 times denser than Blue-Ray optical disc storage technology.
This type of data storage uses three layers nanoscale points on a glass disc. The size, orientation and position (in three dimensions) of the points give the five "dimensions" used to encode the data.
According to investigators, a 5D disk might still be readable after 13.8 billion years, but it would be surprising if someone was still around to read it at the time. In the short term, 5D optical media could also survive after being heated to 1.000 degrees Celsius.
The technique developed by PhD researcher Yuhao Lei uses a femtosecond laser high repetition rate. The process begins with a seeding pulse that creates a nano vacuum, but the fast pulse does not actually need to write data. The repeated weak pulses exploit a phenomenon known as near-field enhancement to sculpt nanostructures in a smoother way. The researchers evaluated laser pulses at different power levels and found a level that speeds up writing without damaging the silica glass disc.
Study reports a maximum data rate of one million voxels per second, but each bit requires several voxels in 5D optical systems. This equates to a data rate of approximately 230 kilobytes per second. At this point, it is possible to fill one of the disks, the capacity of which is estimated at 500 TB. It would take about two months to write such a large amount of data, after which it could not be changed.
"Individuals and organizations are generating ever-larger data sets, creating a desperate need for more efficient forms of data storage with high capacity, low power consumption and a long lifespan," said researcher Yuhao Lei, from the University of Southampton, UK. "While cloud-based systems are more designed for temporary data, we believe that 5D data storage in glass could be useful for longer-term data storage for national archives, museums, libraries, or private organizations." added.
Although the optical storage of 5D data in transparent materials has been demonstrated in the past, it has been shown that it is difficult to write data fast enough and with enough density for real world applications. To overcome this hurdle, the researchers used a high repetition rate femtosecond laser to create tiny wells containing a unique nanolamella-like structure measuring just 500 x 50 nanometers each.
Rather than using the femtosecond laser to write directly on the glass, the researchers harnessed the light to produce an optical phenomenon known as near-field enhancement, in which a nanolamella-like structure is generated by a few weak pulses. nano vacuum generated by a single pulse micro explosion. The use of near-field enhancement to fabricate the nanostructures has minimized thermal damage that has been problematic for other approaches using high-frequency repeating lasers.
Since nanostructures are anisotropic, they produce a birefringence that can be characterized by the orientation of the slow axis of light (4th dimension, corresponding to the orientation of the nanolaminate structure) and the delay force (5th dimension, defined by the nanostructure size). When data is recorded on glass, the orientation of the slow axis and the strength of the delay can be controlled by polarization and light intensity, respectively.
"This new approach improves data writing speed to a practical level, so that we can write tens of gigabytes of data in a reasonable amount of time," Lei said. Highly localized precision nanostructures allow for greater data capacity, as more voxels can be written in a unit volume. In addition, the use of pulsed light reduces the energy required to write. «
The researchers used their new method to write 5 gigabytes of text data to a glass disk. silica the size of a conventional compact disc, with a reading precision of almost 100%. Each voxel contained four bits of information, and both voxels matched one character of text. With the write density offered by the method, the disk could hold 500 terabytes of data. With system updates that allow parallel writing, the researchers say it should be possible to write this amount of data in about 60 days.
With the current system, we have the ability to preserve terabytes of data, which could be used, for example, to preserve the DNA information of a person who is now working to increase the writing speed of his method and make the technology usable outside the laboratory. It will also be necessary to develop faster methods of reading data for practical data warehousing applications.