Beyond Optical Storage

For long we stored data on the surfaces, but today the technology

has moved to volumes. Since the storage needs are increasing exponentially,

technology improvements in current storage media are saturating. And even when

we think that the Blu-Ray disks and HD-DVD would be sufficient to satiate the

storage needs, there is need for more. And that's where the concept of

holographic storage comes from. With volume intensive optical and holographic

storage media coming into the foray, it's no longer that the data need be

stored in layers. Rather it can now be stored all across the thickness of the

storage media, thus, drastically increasing the amount of data that can be

stored on, say, a disk. This has led to a compelling increase in the amount of

data that can be stored over the same size of the disk.

What's holography?

 



But what is meant by holographic storage? Holography is a
branch of optics where the highly coherent laser beam is used. And it is the

three-dimensional nature of holography that enables the superimposing many

layers/pages of data in the same volume of the material using a single beam of

light. Also, holography has the potential for fast transfer rates and fast

random access times. This is because the data are stored and recovered in

parallel-typically 1 million bits at a time.

Reading



and writing data

 



Now lets get into a little more detail and see how the
holographic storage works. As mentioned earlier, the laser beam is used as a

carrier to store data as holograms. For those who know not, holograms are the

interference patterns created in the process. So the laser beam is split into

two-a signal beam that carries the data, and the reference beam. Spatial light

modulators (SLMs) are used to translate the data onto the signal beam. The SLM

encodes the digital data (1s and 0s) into a pattern of light and dark pixels in

an array or page. One such array contains about a million bits. A hologram is

then formed on a photosensitive recording media at a place where the reference

beam and the signal beam carrying data intersect.

Now you must be wondering how the high density of the

holographic media is achieved. Well that's done by varying the position of the

storage medium, wavelength, or the angle at which reference beam meets the

signal beam. That's how comparatively large amounts of data can be stored over

a single disk.Reading the data is equally easy. The data can be recovered

through the hologram reconstructed from the beam that is reflected from the

reference beam at the detector medium.

Challenges

 



Some optical storage media products have already become
hits in the consumer space, the latest entry in the product line is the H-ROM

(Holographic ROM) that stores data on the tapestry HDS (Holographic Data

Storage) media. This is the latest addition to the media product family that

includes green laser HDS3000 media, and blue laser HDS5000 media.

While the media products are now being targeted at its

applications in high-end archiving of data centers, financial institutions,

security and surveillance, and for storing medical data where the data is

currently being stored and archived on magnetic tapes. Magnetic tapes lag behind

the optical media for two main reasons: one, it is harder to access data on

magnetic tapes though they can store large amounts of data and two, they are

less durable for they can store data in good shape for 10 years against the 50

years pitched in by the holographic media.

So the optical and holographic storage media can be used to

replicate, archive and broadcast high-definition videos. So you can imagine the

complete Star Trek series being shipped to you over a single disk with a few

complementary movies in it. And pirates beware! The data on holographic disks is

difficult to copy since it requires the same expensive equipment to replicate it

as is needed to create the original. Another big issue concerns the storage

material used. Since hologrpahy involves laser beams to write the data in

various patterns on a photosensitive material, all the precautions need to be

taken to protect the photosensitive material from getting spoilt. As a result,

the data disks have to kept away from light till a negative film is prepared,

just like any other photographic plate. Even the most efficient of technologies

have become omnipresent only when they have become affordable to the masses. And

holographic media is no exception. So just wait and watch to see how things

unfold on the cost and reliability platforms, and the H-ROM comes at the price

of a CD today.

For long we stored data on the surfaces, but today the

technology has moved to volumes. Since the storage needs are increasing

exponentially, technology improvements in current storage media are saturating.

And even when we think that the Blu-Ray disks and HD-DVD would be sufficient to

satiate the storage needs, there is need for more. And that's where the

concept of holographic storage comes from. With volume intensive optical and

holographic storage media coming into the foray, it's no longer that the data

need be stored in layers. Rather it can now be stored all across the thickness

of the storage media, thus, drastically increasing the amount of data that can

be stored on, say, a disk. This has led to a compelling increase in the amount

of data that can be stored over the same size of the disk.