What is Holographic Storage?

Holographic storage is a type of data storage that utilizes light and holography to create data storage that can be significantly larger and faster than magnetic or optical storage devices. A number of different companies have been working on creating storage devices that use holography to write and read data. Ultimately, despite the potential benefits inherent in this type of storage, other data storage options may prove to be more immediately feasible and cost effective. Holographic storage can be utilized both for single-write media storage as well as rewritable storage, though the latter would require somewhat more complicated technology.

Holography is the use of light, typically two distinct beams of light or energy, to produce a “recording” of an image or data that can then be retrieved through the use of light at a later time. This has historically been used to produce three-dimensional (3D) holographic images, by using light to create a “recording” of an object on a surface made of photo-sensitive material. The 3D image can then be recreated using only light.

A holographic storage device would use the same technology to create “recordings” not for the purposes of creating 3D images, but in order to store data on photo-sensitive materials that could then be housed inside of a hard drive or similar storage device. Basically, two laser beams are used: one is called a reference beam and the other an illumination or signal beam. The two beams create an interference pattern that imprints upon a photo-sensitive material, just like in creating a holographic image. By using another laser beam at the same angle, the data in holographic storage can be retrieved and displayed on a computer screen in the same way that data is retrieved from a magnetic or optical storage device.

Optical and magnetic storage methods record data in strings of individual bits of information, and holographic storage uses the same process. A small area used in holographic storage, however, can hold numerous pieces of data that effectively overlap and can be accessed by changing the angle of the beams used. This means that the same amount of physical space used in holography can store far more data than what is possible when compared to magnetic or optical storage.

Holographic storage can also access the bits of data in a parallel manner, through the beam of light, rather than one bit at a time, making data recording and retrieval significantly faster than other media. Most photo-sensitive material can only provide single writing of data, however, though the information could be read numerous times and would likely last for up to a century. Certain types of crystals could likely be used for rewritable holographic storage since some crystals have properties, called the photorefractive effect, that allow holograms to be recorded multiple times and changed.