3D Optical Data Storage: Definition & Explanation

Instructor: Martin Gibbs

Martin has 16 years experience in Human Resources Information Systems and has a PhD in Information Technology Management. He is an adjunct professor of computer science and computer programming.

This lesson will provide an overview of 3D optical data storage, a leap forward from CD-ROMs and DVD data storage. Two major types of data storage will be examined: 3D storage throughout the volume of the disc and holographic data storage.

3D Optical Storage

Today's optical storage is currently on 2-dimensional medium, e.g., the CD-ROM, DVD, Blu-Ray, etc. While these devices have steadily improved in storage capacity, they are still limited by the fact that data can be written in layers on the disc. 3D storage, on the other hand, isn't limited by the layers: by adding volume to the medium, the storage capacity grows by leaps and bounds. Currently there are two major types of 3D storage: so-called simple storage of data throughout he volume of the disk, and holographic storage.

3D Storage of Data: Localized-Bit

Localized-bit is an extension of standard disc storage: Data is not only available on the surface of the disc but throughout its volume. The laser then reads the data through the medium, instead of across the lands and pits of a traditional CD-ROM or DVD. As of the writing of this lesson, the laser can be used to focus on one bit at a time, or which can read several bits of data at the same time. The technology is still developing, however, and these advances will require changes in hardware in order to read these new types of discs.

The image below is a cross-section of a 3D optical disc and how data is accessed:

3d optical disc

While this method is viable, a solution with much greater storage and retrieval potential is holographic data storage.

Holographic Data Storage

A hologram is a three-dimensional image which is created as light beams (e.g., from a laser) merge together. Typically a laser beam is split into two paths: Data and reference beams are directed into the storage medium such as a crystal. While it might sound like something from Star Wars, holographic storage has very real possibilities and opportunities for implementation.

Storing and Retrieving Data

Data storage and retrieval is non-linear in a 3D system. Therefore, by using light at different angles, the data can be stored throughout the volume of the medium; multiple images can be recorded into the same data area. Millions of bits of data can be stored in parallel, which greatly increases the data transfer rate as compared to standard optical storage. The stored data is read by re-creating the same reference laser beam that created the hologram. As the reference beam's light is cast upon the disc, the light hits a detector and is refracted; this detector reads that data (and can read it in parallel with other data), up to one million bits at a time!

Storage Materials

2D storage is written into lands and pits on a CD or DVD. Holographic data requires volume; thus, the read-write materials include non-living crystals that can interact with light. They are coated with elements like iron or rare-earth ions made in a lab. Other materials could include a photo-polymer (light-sensitive material; think of advanced microfilm), or even photographic film. Another major difference between 3D and 2D is that, when the laser hits the material, there are actual physical and/or chemical changes that occur on the medium!

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