InPhase is coming up with the hardisk that will employ holographic media. It is capable of 3d storage and thus making it possible to achieve 515 GB per square inch storage capacity.

By comparison, magnetic disks, such as those used in the hard drives, can manage a storage density of about 37.5Gb per square inch.
The first generation of InPhase drives will have a capacity of 300Gb on a single disk. InPhase expects to unveil its first holographic drive later this year, with products of up to 1.6 terabyte coming. Technology could eventually lead to a holographic disc that could hold more than 100 DVD-quality movies.

According to InPhase CTO, they have earlier achieved 200 GB per inch capacity in 2005.

Holograms use a three-dimensional image generated by lasers to store information.

Basic concept behind it is storing data in three dimensions throughout the entire thickness of the storage medium, be it a disc, a card or a wafer thin chip. Current magnetic and optical storage devices, such as computer hard drives or CD-ROMs, store data on their surfaces only. Hologram storage mediums also have lifetimes of up to 100 years, compared to the typical 4-year span of the typical hard drive, because they are more resistant to temperature swings, water, acid and electrical fields. The idea is for the lasers to hit the medium at thousands of different angles and depths, utilizing the entire thickness of the medium. By recalling data in packets of millions of bits, downloading from hologram storage is also envisioned as being at least 30 times faster than current storage methods, which read back data one bit at a time.

How is data recorded?
Light from a single laser beam is split into two beams, the signal beam (which carries the data) and the reference beam. The hologram is formed where these two beams intersect in the recording medium.

The process for encoding data onto the signal beam is accomplished by a device called a spatial light modulator (SLM). The SLM translates the electronic data of 0’s and 1’s into an optical "checkerboard" pattern of light and dark pixels. The data is arranged in an array or page of around a million bits. The exact number of bits is determined by the pixel count of the SLM.

At the point of intersection of the reference beam and the data carrying signal beam, the hologram is recorded in the light sensitive storage medium. A chemical reaction occurs in the medium when the bright elements of the signal beam intersect the reference beam, causing the hologram stored. By varying the reference beam angle, wavelength, or media position many different holograms can be recorded in the same volume of material.

How is data read?
In order to read the data, the reference beam deflects off the hologram thus reconstructing the stored information. This hologram is then projected onto a detector that reads the data in parallel. This parallel read out of data provides holography with its fast transfer rates.

What is all about media?
The Tapestry™ storage medium satisfies the many stringent criteria for a viable storage material including high dynamic range, high photosensitivity, dimensional stability, optical clarity, manufacturability, nondestructive readout, thickness, and environmental and thermal stability.

In addition to developing a new class of materials, InPhase Technologies also developed the ZeroWave™ manufacturing processes, which enables the cost effective fabrication of optically flat media. This makes the media price competitive for mass consumption.

Add this to your personal book library :-
http://www.inphase-technologies.com/...holobasics.pdf

Thanks asm for bringing this breakthrough to my knowledge.
Credits also goes to Mayet.