High-speed laser writing method could pack 500 terabytes of data into CD-sized glass disc

Researchers have developed a fast, energy-efficient laser-writing technique to create nanostructures in silica. The method allowed them to store 6GB of data in a 1-inch silica-glass sample. Each of the four squares shown measures 8.8 X 8.8mm. Laser-writing was also used to mark the glass with the university logo. Credit: Yuhao Lei, Peter G. Kazansky University of Southampton
Researchers have created a laser-writing process that produces high-density nanostructures made of silica glass. It is fast and efficient. These structures can be used to store long-term optical data storage in five dimensions (5D), which is more than 10,000 times dense than Blue-Ray optical disk storage technology.

Yuhao Lei, a doctoral researcher at the University of Southampton, said that "individuals and organizations are creating ever-larger data sets, which creates the need for more efficient forms of storage with a high capability, low energy consumption, and long life." While cloud-based systems can be used for temporary data, 5D data storage in glass may be more suitable for long-term storage of data for national archives, museums and libraries, as well as private organizations.

Lei and his colleagues present their new method of writing data in Optica, Optica Publishing Group’s journal. It includes two optical dimensions as well as three spatial dimensions. This new method can write at speeds up to 1,000,000 voxels per Second, which is roughly equivalent to recording more than 230 kilobytes (more than 100 pages) of data per second.

Lei stated that the physical mechanism used is "generic". "This energy-efficient writing technique could be used to fast nanostructuring transparent materials for 3D integrated optics or microfluidics applications," Lei said.

Faster, better laser writing

Although optical data storage in 5D has been demonstrated previously, it has proven difficult to write data fast enough with enough density to be useful for real-world applications. The researchers created tiny pits with a single nanolamella-like structure using a femtosecond light source at a high repetition rate. This was done to overcome this problem.

Instead of using the femtosecond light laser to write directly into the glass, researchers harnessed light to create an optical phenomenon called near-field enhancement. This is where a few weak light pulses are used to form a nanolamella-like structure from an isotropic microexplosion. Near-field enhancement was used to create the nanostructures. This minimized thermal damage that can be caused by other methods that use high repetition-rate lasers.

Anisotropic nanostructures produce birefringence. This can be measured by the light's slow orientation (4th dimension, which corresponds to the orientation of the nanolamellalike structure) or strength of retardance (5thdimension, which is determined by the size and shape of the nanostructure). The polarization and intensity can control the strength of retardance and slow axis orientation of the data that is being recorded into the glass.

Lei stated that "This new approach increases the speed of data writing to a practical level so we can write tens or gigabytes worth of data in reasonable time." "Highly localized precision nanostructures allow for higher data capacities because there are more voxels per unit volume. Pulsed light also reduces the amount of energy required to write.

Write data on a CD-ROM made of glass

Researchers used their new method for writing 5 gigabytes worth of text data onto silica glass discs that were about the same size as a standard compact disc. The disc was read out almost 100% accurately. Each voxel contained 4 bits of information and each voxel corresponded with a text character. The disc could hold 500 terabytes worth of data, based on the writing density that was available. Researchers believe it is possible to write this much data in 60 days with parallel writing upgrades to the system.

Peter G. Kazansky (leader of the research team) stated that "with the current system we have the capability to preserve terabytes data, which could possibly be used, for instance, to preserve information derived from a person’s DNA."

Researchers are currently working on improving the writing speed and making the technology more accessible outside of the laboratory. Practical data storage applications will require faster data reading methods.

More information: Yuhao Lei and colleagues, High speed ultrafast laser anisotropic nanostructuring via energy deposition control via near field enhancement, Optica (2021). Information from the Journal: Optica Yuhao Lei and colleagues, High speed ultrafast lasotropic nanostructuring via energy deposition control via close-field enhancement (2021). DOI: 10.1364/OPTICA.433765