Date:13/04/18

Holographic data storage could cram 1,000 DVDs onto a 4-in square film

While technology is getting better at cramming more and more data on discs and drives, there's another whole dimension that's essentially going unused. Holographic storage devices could make use of that, and now a team of Chinese scientists has developed a new nanoparticle-based film that can store information as 3D holograms, improving data density, read and write speeds and stability in harsh conditions.
 
The idea of holographic storage has been around for decades, but progress has been slow. In 2005 several major tech companies got together to promote the development of Holographic Versatile Discs (HVDs), as well as holographic drives and cards. GE had a crack at a similar system in 2009, but nothing has really eventuated since – or nothing commercial, at least.
 
Researchers have been hard at work trying to develop the technology, and a team from Northeast Normal University in China has created a new kind of film that solves some of the problems plaguing previous studies. The scientists started with a semiconductor film made of titanium dioxide (or titania), and nanoparticles of silver. A laser writes information to the silver nanoparticles by changing their charge, and since different wavelengths of the laser light affect the particles differently, the data is stored as 3D holograms.
 
That allows these devices to store more data in less physical space than conventional optical systems. According to the Northeast Normal team, a piece of the new holographic film measuring 10 x 10 cm (4 x 4 in) and just 620 nanometers thick can store 1,000 times more data than a DVD. Assuming they're talking about the commonly-used dual-layer DVD, that means the holographic film could store roughly 8.5 TB.
 
But the problem with most holographic storage prototypes is that external UV light can erase the data. That doesn't bode well for the long-term stability of the technology, particularly in outdoor environments or in space.
 
So, the researchers added a new safety measure to the mix: Electron-accepting molecules between one and two nanometers wide. Because these molecules are so small, they're able to sit inside the pores of the semiconductor film without affecting the honeycomb-shaped structure of those pores. Once there, these molecules catch excess electrons introduced by the UV light, before they can wreak havoc on the silver nanoparticles.
 
"We noticed that UV light could erase the data because it caused electrons to transfer from the semiconductor film to the metal nanoparticles, inducing the same photo transformation as the laser," says Shencheng Fu, lead researcher on the study. "Introducing electron-accepting molecules into the system causes some of the electrons to flow from the semiconductor to these molecules, weakening the ability of UV light to erase the data and creating an environmentally stable high-density data storage medium."
 
In tests, the team was able to write data to the film efficiently, even while it was exposed to UV light. Better yet, the electron-accepting molecules added another unexpected advantage, improving the read and write speed by giving electrons more paths to travel through. The team says that data can be retrieved at speeds of up to 1 GB per second.
 
"In the future, these new films could be incorporated into a tiny storage chip that records 3D color information that could later be viewed as a 3D hologram with realistic detail," says Fu. "Because the storage medium is environmentally stable, the device could be used outside or even brought into the harsh radiation conditions of outer space."
 
For the next stage of the research, the team plans to test out the material's resistance to UV light in outdoor tests.

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