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Vimal Singh GIT.
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Introduction
Basic Components
Working Principle
Applications &
Conclusion
Capacity: 700 mb
Capacity: 4.7 Gb Capacity: 30-50 Gb Capacity: 1-4 Tb
What is Holographic Memory ?
• It is a memory that can store information
in form of holographic image.
• It is a technique that can store
information at high density inside crystals
or photopolymers.
• It provides data to be written beneath the
surface of the disc.
• Holographic memory can store up to 1 Tb
in a storage medium the size of a sugar
cube crystal.
Why do we need this ?
• “For Internet applications alone, industry estimates are
that storage needs are doubling every 100 days”
• By the year 2010, a storage system serving an average
LAN will need … 100 TB and a WAN server will require
10TB to 1 petabyte …of storage” (Red Herring)
Basic Components
spatial light modulator
LCD panel
To direct
the laser
beams
To spilt
the laser
beam
photopolymer
Lithiumniobate
crystal
Mirrors
Beam
splitters
CCD
camera
Blue-green
argon laser
Interprets
the digital
information
Working Principle
Continues..
Creating Holograms
Pattern left on media
Reconstructing the image
Shift Characteristics
Read-out
Shift:
Page Data
Y
X
1μm pitch
1μm
Shift multiplexing
read/write can be
done at 3μpitch
2μm
3μm
Properties of Hologram
•A block or sheet of photosensitive material which
records the diffraction of two light sources.
•A laser beam is splatted into two beams:
 Source beam
 Reference beam
•The two beams diffracts to form the image on the
recording medium
Spatial light modulator
•It is used for creating binary information out of
laser light.
•It is a 2D plane, consisting of pixels which can be
turned on and off to create binary 1.s and 0.s.
•It contains a two-dimensional array of windows,
which are only microns wide.
Page Data Access
•As the data is stored in the form of holograms,
data retrieval must be in the same form.
•So, a holographic system sends data in the form
of pages.
•It provides fast access times.
Error Correction
•As the density of data is massive, it is prone to
errors.
•Errors can be controlled by:
o Recording errors
o Page level parity bits
o Interfacing
Recording Errors
•Cause: Noise generated by laser beam
•Result: Can change a binary 0 to binary 1
•Possible Solution: Improvement in laser beam
and recording material
Page-level Parity Bits
•Data is stored in the form of 2-D array
•Odd no. of bits accounts for parity 1
•Even no. of bits accounts for parity 0
•Parity check bits are used
to identify any errors present
in the array
Interfacing
•While reading the data, they are sent to the
computer as sheets.
•Such thing may exceed the processor
throughput
•Remedy: Defining set of rules which can be
used for correction and reading of data
efficiently.
Applications
1
Data Mining
2
Petaflop Computing
3
Future Computer Systems
4
Conclusion
• Built on technology that’s around for 40+ years
• Holographic Memory is the future of data storage
o HUGE capacity, Very fast, Smaller
o Parallel processing
• Current storage methods nearing there fundamental
limits of storage density
• Large market and little new competition