•The rate of advancement in storage technology has been truly
•How ever we are fast approaching the physical limit for storing
information on media such as magnetic platters of hard disk or the
chemical layers in optical layers such as CD’s and DVD’s
•Research in these fields has created storage solutions such as
•Holographic data storage is a breakthrough technology that literally goes beneath the
surface of the media and stores information within its volume.
• Holographic data storage (HDS), which makes use of full volume of the recording
medium, possesses high potential by promising fast transfer rates of hundreds of
Megabytes/sec and storage densities greater than 200 Gbytes per 120mm disk.
•The two different systems that are discussed here include plane Wave and Digital
Holographic Data Storage. These measured characteristics include high dynamic range,
sensitivity, and small recording-induced Bragg detuning. In addition, results of archival
and shelf-life environmental testing of the media will be discussed.
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.
•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?
•The interference pattern induces modulations in the refractive index of the recording
material yielding diffractive volume gratings. The reference beam is used during
readout to diffract off of the recorded gratings, reconstructing the stored array of bits.
•The reconstructed array is projected onto a pixelated detector that reads the data in
parallel. This parallel readout of data provides holography with its fast data transfer
rates (10's to 100's of MBytes/second
•The readout of data depends sensitively upon the characteristics of the reference beam.
By varying the reference beam, for example by changing its angle of incidence or
wavelength, many different data pages can be recorded in the same volume of material
and read out by applying a reference beam identical to that used during writing. This
process of multiplexing data yields the enormous storage capacity of holography.
•While the development of the needed components has been
accomplished for non holographic markets, the volume of these markets
is expected to lead to low-cost, reliable components for holographic data
•Holographic Data Storage is used for Data Mining and Data
Warehousing. The data transfer rate is very high.
•Holography allows a million bits of data to be written and read in parallel with a
single flash of light. This enables transfer rates significantly higher than current optical
•The main advantage is the speed of retrieving the data. Such systems will be able to
retrieve data in tens of microseconds as compared to a data access time of almost 10
milliseconds offered by the fastest hard disks.
• Another very important advantage is that of information search and retrieval.
•The flexibility of the technology allows for the development of a wide variety of
holographic storage products that range from handheld devices for consumers to storage
products for the enterprise
With so many materials and techniques being explored, one can’t
assume that storage will always be magnetic disks, or that memory will
always be dynamic RAM. Systems of the future may build upon the
concepts that exist today, or they may employee entirely new
technologies such as holographic memory.
-Jasubhai Digital Media
-Jasubhai Digital Media