Holography & the Basics of Holographic Storage

Holography is a technique where an object is imaged in a way that, when viewed later, it appears three dimensional (3D). This is the basic method of generating holograms, which are increasingly used in a variety of fields: art, security, data storage, and so on. In this article, we will focus on the possibilities of holographic data storage.


Why is There a Need for Holographic Storage?

Archival storage is a necessary part of every enterprise’s ability to meet compliance requirements and address litigation issues, however deep archiving is still a challenge. Tape is removable and securable but arouses concerns with long-term reliability and readability.


How Does Holographic Storage Work?

In holographic storage, a light field is produced by a laser source that illuminates both the object and the recording media. The scattered light from the object interferes with the reference light, creating a subsequent interference pattern that produces the image. Let us explore this in more depth.


Holographic storage works by storing a sequence of discrete data snapshots within the thickness of the media. When a laser beam is split into two signals, the storage process begins. One beam is used as a reference signal and the other beam (known as the data-carrying beam) is passed through a device called a special light modulator (SLM). This acts as a fine shutter system, passing and blocking light at points corresponding to ones and zeroes.


The reference beam is then reflected to impose on the data-carrying beam within the media. This produces a three-dimensional refraction pattern (the hologram) that is captured in the media. Holographic storage employs circular media, much like a blank CD/DVD that spins to accept data across a continuous spiral data bath. When the media is written, data is read back with the reference beam illuminating the refraction.


The three-dimensional aspect of data recording is a critical difference between holographic storage and standard CD/DVD recording. Traditional optical media employs a single laser beam to write data in two dimensions along a continuous spiral data bath. Conversely, prototype holographic storage products can save one million pixels at a time in discrete snapshots, also known as pages, which form microscopic cones through the thickness of the light-sensitive media. Over 4.4 million individual pages can be stored on a disc.


Benefits of Holographic Storage

For deep archiving purposes, long-term media stability and reliability are compelling advantages of holographic storage, particularly over tape and discs which cannot ensure reliability over time. Holographic storage is also portable, allowing the distribution of dense data that cannot be easily sent across other networks such as broadcast or high-definition video.


Holography and holographic storage is also appealing for short term backups and archives as companies are beginning to rely less and less on tape backups. Holographic storage attached to a virtual tape library could be a beneficial replacement to tapes.


Holographic storage capacity and performance is below current disc and tape systems, however they compare favorably to existing optical storage devices.


As holography and holographic storage technology is generally focused on a niche in the storage market, more capable and cost-effective systems may take a while to be produced. However, the possible introduction of hybrid holographic media could speed up this process. If you would like to learn more about holographic storage, or the importance of precision optics in holography, contact a us today.