Advances make high density, 5D optical storage practical for long-term data archiving.
Researchers developed a fast & energy-efficient laser writing method for producing high-density nanostructures in silica glass. These tiny structures may be used for long-term five-dimensional (5D) optical data storage which is greater than 10,000 times denser than Blue-Ray optical disc storage technology.
“Individuals & organizations are generating ever-larger datasets, creating the desperate required for greater efficient forms of data storage with a high capacity, low energy consumption & long lifetime,” said doctoral researcher Yuhao Lei from University of Southampton in UK. “While cloud-based systems are designed more for temporary data, we believe that five-dimensional data storage in glass could be useful for longer-term data-storage for national archives, museums, libraries, or private organizations.”
In Optica, the Optica Publishing Group’s journal for high impact research, Lei & colleagues describe their new method for writing data that encompasses 2 optical dimensions plus 3 spatial dimensions. The new-approach can write at speeds of 1,000,000 voxels per second that is equivalent to recording around 230 kilobytes of data (greater than 100 pages of text) per second.
“The physical mechanism we use is generic,” said Lei. “Thus, we anticipate that this energy efficient writing method could even be used for fast nano-structuring in transparent materials for applications in three-dimensional integrated optics & microfluidics.”
Faster, better laser writing
Although five-dimensional optical data storage in transparent materials are demonstrated before, writing data fast enough and with a high-enough density for real world applications proved challenging. To overcome this hurdle, researchers used a femtosecond laser with a high-repetition rate to make tiny pits containing a single nanolamella-like-structure measuring only 500 by 50 nanometres each.
Instead of using femtosecond laser to write directly in glass, researchers harnessed the light to produce an optical-phenomenon referred as near-field enhancement, in which a nanolamella-like-structure is created by a few weak light pulses, from an isotropic nanovoid generated by a single pulse micro-explosion. Using near-field enhancement to create the nanostructures minimized the thermal damage that are problematic for other approaches that use high repetition rate lasers.
Because nanostructures are anisotropic, they produce birefringence that can be characterized-by light’s slow axis orientation (4th dimension, corresponding to the orientation of nanolamella-like structure) and strength of retardance (5th dimension, defined by size of nanostructure). As data is recorded into glass, slow axis orientation & strength of retardance can be controlled by the polarization & intensity of light, respectively.
“This new approach improves the data writing speed to a practical-level, so we can write tens of gigabytes of data in a reasonable time,” said Lei. “The highly-localized, precision nanostructures enable a higher-data capacity because more voxels can be written in a unit volume. In addition, using the pulsed light reduces the energy required for writing.”
Writing data on a glass CD
The researchers used their new method to write five gigabytes of text data onto a silica glass disc about the size of a conventional-compact disc with roughly 100 percent read-out accuracy. Each voxel contained 4 bits of information and every 2 voxels corresponded to a text character. With writing density available from the method, disc would be able to hold 500 terabytes of data. With upgrades to system which allow parallel writing, researchers say it should be feasible to write this amount of data in about sixty days.
“With current system, we have the ability to preserve terabytes of data that could be used, for instance, to preserve information from a person’s DNA,” said Peter G. Kazansky, leader of researcher team.
The researchers are recently working to increase the writing-speed of their method and to make the technology usable outside the laboratory. Faster methods for reading data will even have to be developed for practical-data storage applications.
The research were published on Optica.