High Density, High Performance, Holographic Data …(1) Presented at the THIC Meeting at the Naval...
Transcript of High Density, High Performance, Holographic Data …(1) Presented at the THIC Meeting at the Naval...
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Presented at the THIC Meeting at the Naval Surface Warfare Center Carderock, 9500 MacArthur Blvd
West Bethesda MD 20817-5700October 3, 2000
High Density, High Performance, High Density, High Performance, Holographic Data Storage:Holographic Data Storage:
Viable at last?Viable at last?William L. Wilson
Photonics Materials Research DepartmentBell Laboratories, Lucent Technologies
Murray Hill NJ 07974Phone:+1-908-582-7919, Fax:+1-908-582-3958
E-mail: [email protected]
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• Introduction to holography• Optical storage via volume holography• Technology review and current status• Conclusion and prognosis
High Density, High Performance, High Density, High Performance, Holographic Data StorageHolographic Data Storage::
Viable at last?Viable at last?William L. WilsonPhotonics Materials Research DepartmentBell Laboratories, Lucent TechnologiesMurray Hill, NJ 07974
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SystemKevin CurtisWilliam WilsonMike TackittAdrian HillTom RichardsonPeter LittlewoodPartha MitraScott Campbell
Material Lisa DharAlex HarrisMarcia SchillingHoward KatzMelinda SchnoesArturo HaleCarol BoydAdam Olsen
Partial List of ContributorsPartial List of Contributors
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Holography PrimmerHolography Primmer
*Total recording of the optical field
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Holographic Recording FundamentalsHolographic Recording Fundamentals
• Parallel readout of data - fast rates• Multiplexing - much greater density
The Holographic “Advantage”The Holographic “Advantage”
Storage of many holograms in the same volume with selective addressing of the individual holograms generates density!!
•Angle Multiplexing*•Wavelength Multiplexing*•Shift Multiplexing*•Peristropic Multiplexing•Phase-code Multiplexing*
*Most techniques are based on or drivenby the Bragg effect or strongly enhanced by Bragg processes
Issue: How do we access each hologram independently?(Selectivity, allows us to exceed the diffraction limit)
The Bragg EffectThe Bragg Effect
Constructive interferenceachieved at specific θ
for a given Λ
The higher the number of scattering planes,The finer the angular or wavelength resolution!!
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Bragg Selectivity of Volume HologramsBragg Selectivity of Volume Holograms
Angular Selectivity of 38 um thick photopolymer film
•• change anglechange angle•• change wavelength change wavelength
-2 -1 0 1 2
0.0
0.2
0.4
0.6
0.8
1.0
Deviation from Bragg (Degrees)
Diff
.Int
(A
U)
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Promise of Holographic StoragePromise of Holographic Storage
The Dream? Maximum density >1bit/λ3
**The Library of Congress on a sugar cube!!**The Library of Congress on a sugar cube!!**The Library of Congress on a sugar cube!!**The Library of Congress on a sugar cube!!**The Library of Congress on a sugar cube!!**The Library of Congress on a sugar cube!!**The Library of Congress on a sugar cube!!**The Library of Congress on a sugar cube!!
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We are not the First!We are not the First!
Bernhard Hill, Philips LabsBernhard Hill, Philips Labs“Advances in Holography”, 1976“Advances in Holography”, 1976
“The Essential Components of a Block“The Essential Components of a Block--organized Holographic Memory”organized Holographic Memory”
44A laser SourceA laser Source44A laser beam deflector*A laser beam deflector*44A fly’s eye lens A fly’s eye lens 44A page composerA page composer44A detector arrayA detector array44A storage matrix**A storage matrix**
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Past Problems with HolographyPast Problems with Holography
• Material - No acceptable material and mediarequirements were ill defined.
• Methods - Complex and difficult, limited density
• Lasers - Extremely costly and unreliable
• Detector - Cost and performance
• SLM - Performance at issue, (frame rates, throughput, etc.)
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But we can’t ignore the technology!But we can’t ignore the technology!
1980 1985 1990 1995 2000
1
10
100
1000
10000
Cap
acity
, GB
ytes
/(51 / 4"
Dis
k)
Library of Congress
100 Movies
1 Movie (DVD)
1996 CD-ROM
Characteristics: High Transfer Rates - > 1GB/secHigh Density - initially 500 Gbytes on a 5-1/4 formatLow Cost/MB - comparable to tapeWrite Once, Removable storage - WORMParallel Read/Write - page access instead of bit access
Holographic StorageHolographic Storage
Industry TrendIndustry Trend
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Past Problems with HolographyPast Problems with Holography
• Material - No acceptable material and mediarequirements were ill defined.
• Methods - Complex and difficult, limited density
• Lasers - Extremely costly and unreliable
• Detector - Cost and performance
• SLM - Performance at issue, (frame rates, throughput, etc.)
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Holographic Recording FundamentalsHolographic Recording Fundamentals::TranslationalTranslational/Shift Multiplexing/Shift Multiplexing
Material
Object
ReferenceHologram formsin Overlap Region
• Parallel readout of data - fast rates• leverages current technologies
Shift direction
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New Method: Correlation Multiplexing (CM)New Method: Correlation Multiplexing (CM)
• Simple to implement• Selectivity independent of material thickness• ~5x density over other holographic approaches • Written 16,000 ~300Kbit holograms at 350 bits/um2
-10-5
05
10 -10
-5
05
10
0
20
40
60
Diffr
acte
d In
tens
.
∆Y (µm
)
∆X (µm)
Signal Beam
Multiplex by moving the mediumReference
Beam
Selectivity Map
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Array of Stored HologramsArray of Stored Holograms
∆x
30µmHologramDia. ~3mm
30µm
∆y
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-75 -50 -25 0 25 50 75
75
50
25
0
-25
-50
-75
∆X Microns
∆Y M
icro
ns
0.5 0.6 0.7 0.8 0.9 1.0
Intensity (arb. units)
Hologram FidelityHologram Fidelity
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500 1000 1500 2000 2500 3000
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
< η > ~ 10-5
~50% Overhead for Channel Modulation and ECCRaw BER O~10-5
ampl
itude
SN
R
Hologram number
First hologram
Last hologram
Density:Density:~48 channel bits/~48 channel bits/µµmm22
Data Stored and Recovered Data Stored and Recovered from Polymeric Mediafrom Polymeric Media
Methods, Methods, a Prognosisa Prognosis
•New innovative simple methods developed!•High density recording demonstrated•High fidelity holograms recorded
Physics not our problem!!
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Past Problems with HolographyPast Problems with Holography
• Material - No acceptable material and mediarequirements were ill defined.
• Methods - Complex and difficult, limited density
• Lasers - Extremely costly and unreliable
• Detector - Cost and performance
• SLM - Performance at issue, (frame rates, throughput, etc.)
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Dynamic Range - High storage densities & rapid read rates
Photosensitivity - Rapid write rates
Millimeter Thickness - High storage densities
Dimensional Stability - High fidelity data recovery
Optical Flatness - High fidelity imaging of data pages
Low Scatter - Low levels of noise in data recovery
Processing - Heat/Solvent Free
Non-volatile readout
Long shelf-life of media
Long archival life of stored data
Environmental/thermal stability
Requirements for holographic storage media
High Storage Capacity
Rapid Write/Read Rates
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Past Candidates for Materials for Holographic Data Past Candidates for Materials for Holographic Data StorageStorage
LiNbO3Volatile ReadoutLow photosensitivityLow dynamic range
Photorefractive polymersVolatile ReadoutRequirement of poling voltages (large)Low photosensitivity
Photopolymers . . .
What’s the problem?
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Material Dynamic Range is King!Material Dynamic Range is King!
**But an overall system view is Queen!!
Materials Systems
•System capacity determines the density needed a fixed media size•Density at fixed media size provides M•Power budget effects minimal ηηηη•Signal detection floor effect limiting ηηηη
You need to decide what to build!
M/# as Standard MetricM/# as Standard Metric
Can be used as a empirical parameter for any material system!
η = (M/#/M)2
*a much better metric for storage!
In general, for all systems the diffractedintensity of an ensemble of holograms
written under identical conditionsscales as
1/M2
The M-number allow us to quantify a materialsutility as a storage media.
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Our View: Go WORM/ROMOur View: Go WORM/ROM
Punt read/write, and try to solve other problems with the technology
• Concentrate on a WORM or ROM basedsystem to shake out technology
Materials for our assessment: PhotopolymersMaterials for our assessment: Photopolymers
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System consists of monomers dissolved in a matrix.
Holographic exposure produces a spatial pattern of photoinitiated polymerization.
Concentration gradient in unreacted monomers induces diffusion of species.
Diffusion produces a compositional gradient, establishing a refractive index grating.
• High photosensitivity
• Permanent holograms
• Low cost
Mechanism
Advantages
Grating Formation in Conventional Photopolymer SystemsGrating Formation in Conventional Photopolymer Systems
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0
1
2
3
4
5
6
7
8
9
10Dynamic Range in Bell Labs LowDynamic Range in Bell Labs Low--TTgg Photopolymer Media:Photopolymer Media:
Date
M#
@ 2
00 µµ µµ
m
6/95
9/95
8/97
1/98
7/96
Goal: M# = 6 @ 200 µm( M# = 30 @ 1 mm)
Measurements performed in materials exhibiting 0.3% shrinkage during recording
3/98
Moore’s Law
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Interferogram of aPhotopolymer-Based Disk
Data page is imaged through sample with a
raw BER ~ 1x10-6.
Optical Quality in LowOptical Quality in Low TTgg Photopolymer MaterialsPhotopolymer Materials
/cm flatness achieved in 1 mm thick media 3’’x3’’λ10
100 Å
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Optical Quality: Pixel Matching with Low Bit Error Rates
-0.5 0.0 0.5 1.0 1.5 2.00
50
100
150
Num
ber o
f Pix
els
Normalized Pixel Intensities
-0.5 0.0 0.5 1.0 1.5 2.01
10
100
Num
ber o
f Pix
els
Normalized Pixel Intensities
Transmitted 800x600 data page
Expanded view of corner pixels
Histogram of pixel intensities, a measure of fidelity of data recovery.
Raw BER ~ 10-6
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Demonstrated Density in Photopolymer MediaDemonstrated Density in Photopolymer Media
Jan '96Jul '96
Jan '97Jun '98
Jul '98Aug '98
0.01
0.1
1
10
100
Den
sity
(bits
/µµ µµm
2 )
0.01
0.1
1
10
100
GB
ytes
/ (5
1 / 4" D
isk)
Channel DensityUser Density - Material 1User Density - Material 2
CD-ROM user density
(0.4 bits/mm 2)
DVD user density
(4.4 bits/mm 2)
New Material and
System Development
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WORM Media Capabilities - 5.25” diskCurrentMaterial(650 nm,
50 mW laser)
CurrentMaterial(532 nm,
50 mW laser)
CurrentMaterial(425 nm,
15 mW laser)
User Capacityper disk(channel density)
150 GB(106
Gbits/in2)
250 GB(175
Gbits/in2)
400 GB(300 Gbits/in2)
Write Rate 20 MB/sec 23 MB/sec 20 MB/sec
Read Rate 70 MB/sec 64 MB/sec 40 MB/sec(limited by
laser power)
Conclusions
Design, fabrication, & demonstration of high-performance photopolymer media for high density holographic data storage
!!!! High dynamic range, high photosensitivity with controlled recording-induced dimensional change
!!!! Optically flat, millimeter-thick, low scatter formats
!!!! Demonstrated high density digital data storage capabilities
Currently in program with Imation Corporation to further jointly develop the photopolymer media.
Materials, Materials, a Prognosisa Prognosis
•New strategy developed!•All issues on the table!•High M# media in hand! •Requirements out in the open•High density digital recording demonstrated•Digital data recovered at low BER, (10-5)
*Still the key problem, but on the run!!
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Past Problems with HolographyPast Problems with Holography
• Material - No acceptable material and mediarequirements were ill defined.
• Methods - Complex and difficult, limited density
• Lasers - Extremely costly and unreliable
• Detector - Cost and performance
• SLM - Performance at issue, (frame rates, throughput, etc.)
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Component SummaryComponent Summary
• SLM - DMD Status– Fixed Problems with windows– 2,000 frames/sec– 80% light throughput– Contrast, ~1000:1– 800x600 pixels
• Detectors - CMOS Cameras – Custom detector functioning– Cheaper to produce than CCDs
=>$300 going to $30– Lower power, Less heat, Lower noise
• Laser - uchip/small cavity– Tested Uniphase and Micracor models– Cost, ~$2K going to $20– High volume is possible– Power, 200-600mW
Components, Components, a Prognosisa Prognosis
•All driven by other technologies!•SLM a commercial product•Camera soon to be a commercial high volume item
Only laser at issue, problem: price!!
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DEMO: System ArchitectureDEMO: System Architecture100mW laser
SLM
Stages & Sample
CMOSCamera
HOE for Reference 1 x 2 foot area
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System RisksSystem Risks
• Engineering and Drive Design• Long term life issues for Media and
Components• Market
If you build it will they buy???
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Past Problems with HolographyPast Problems with Holography(Current Status)(Current Status)
• Material - Two chemistry materials class has been developed, study of issues relevant to manufacture underway
• Methods - An array of simple, high density method developed. A compact demonstration device built, (1ft x 2ft).
• Laser - Moderate to low cost options coming on line.
• Detector - Optimal device type in hand.
• SLM - High throughput, fast frame rate devices available.