Scientists create the first graphene-based holographic optical disc

Scientists in Australia have succeeded in creating the first graphene-based optical disc. Owing to the magical properties of graphene, we’re not just talking about a Blu-ray or DVD disc that has had its recording layer replaced with graphene, either — we’re talking about holographic storage with absolutely monumental capacity, intrinsically high security, and apparently the ability to recover the data even when the discs are broken.

The research, carried out by Min Gu and friends at the Swinburne University of Technology in Melbourne, started with a suspension of graphene oxide (GO) in water. The suspension was then mixed with PVA (polyvinyl alcohol), spun coated on a glass disc, and left to dry. The end result is a disc covered in a GO polymer. This GO polymer is naturally highly fluorescent — but, by shining a two-photon femtosecond laser at the polymer, it can be turned into reduced GO, which isn’t fluorescent. (Reduced GO is essentially low-grade graphene.) It’s then easy enough to use another laser, paired with a photodetector, to read these non-fluorescent areas. Voila: Reading and writing to a GO-polymer optical disc.

If that wasn’t exciting enough, the recording layer of these GO-polymer discs is thick enough that the read/write lasers can be focused onto multiple layers. The refractive index of the reduced GO can also be modulated, depending on how the recording laser is used. With these two factors combined, these GO-polymyer discs can be used as holographic storage. Without getting into the complexity of how holographic storage works, it’s enough to say that it allows for incredibly high storage densities. In this case, the Australians say they’ve reached a density of around 0.2 terabits per cubic centimeter, or 3.2 terabits per cubic inch. It’s hard to compare holographic to non-holographic storage, but hard drives are slowly creeping towards 1 terabit per square inch, while Blu-ray discs are a few orders of magnitude less, in the gigabits-per-square-inch range.

In keeping with their national identity, these are two holograms written by the Australian researchers onto the GO-polymer disc

Curiously, while the research paper doesn’t mention it, the lead researcher, Min Gu, claims that these GO-polymer discs aren’t just good for storing lots of data. “Conventionally, information is recorded as binary data in a disc. If the disc is broken, the information cannot be retrieved.. the new material allows the development of super-discs, which will enable information to be retrieved – even from broken pieces.” Gu doesn’t say how the data would be retrieved, but presumably it has something to do with its holographic nature.

As we’ve reported previously, one of the main stumbling blocks when it comes to the commercial adoption of graphene is its mass production. There is currently no way of producing large amounts of high-quality graphene. The reduction of graphene oxide to graphene is of particular interest because it’s easy and can be done in bulk — but so far, the resulting graphene is of low quality. Still, this hasn’t prevented cool research like the work here carried out by Swinburne, and similar work done by UCLA which used a DVD burner to create graphene that was then used in the construction of uber supercapacitors.

[The image at the top of the story is a Blu-ray disc, not the new GO-polymer disc created by Swinburne.]

Now read: 3D graphene nanoballs could make supercapacitors more super

Research paper: doi:10.1038/srep02819 – “Giant refractive-index modulation by two-photon reduction of fluorescent graphene oxides for multimode optical recording” [Free PDF!]