How It Works
Holographic Storage is a totally new way of storing digital data. It works by splitting a blue laser beam in two, a reference beam and a data beam. The data beam is modulated with a spatial light modulator (like in a digital projector) that creates a very high density array of 1.5 million pixels. Where the data beam and the reference beam intersect, a holographic interference pattern is formed. When focused on an unexposed, light sensitive holographic disk, a permanent 3D holographic image is formed in the light sensitive layer of the disk. To recover the data from the disk, a reference laser is focused on the disk and an image of the original digital array is formed and captured on a CCD image sensor.
Once the image containing 1.5Mbits of data is written to the disk, the angle of the reference beam is moved slightly and another 1.5Mbits can be written in the same 3D volume as the first image. This process is repeated many times with slightly different reference beam angles to create multiple, non-interfering data images in the same volume of the disk. Then the disk is rotated slightly to the next area of the disk and the multiple write sequence is repeated. Unlike magnetic Hard Drives and optical disks such as CD, DVD and Blu-Ray, where bits are written one bit at a time onto a spinning disk, holographic data storage reads and writes 1.5Mbits at a time on a stationary disk. This results in improved read and write speeds as well as much lower power consumption because there is no need to spin the disk constantly.
Once the disk is exposed with the data to be saved, the disk is cured with the laser which is analogous to developing and fixing photographic film. Once developed, black and white photographic film is no longer light sensitive and is relatively inert, which gives it very good long term image retention. Similarly, holographic disks become inert once they are cured they become unalterable by natural elements, human errors or tampering. Accelerated life testing indicates that holographic disks can store their digital data safely for over 50 years with no loss of data.