the future direction of optical data storage

The Future Direction of Optical Data Storage

Technologies and Challenges in the 21Technologies and Challenges in the 21stst CenturyCentury

Media-Tech 2006 Long BeachLong Beach, California

October 10-11, 2006

< by >Richard G. Zech, Ph.D.

Consultant & Expert Witness - Computer Storage & PhotonicsPresident & Managing Principal

The ADVanced ENTerprises (ADVENT) GroupColorado Springs, CO 80906

(719) 633-4377 v [email protected]

mailto:[email protected]

October 10, 2006 The ADVanced ENTerprises (ADVENT) GroupThe ADVanced ENTerprises (ADVENT) Group 22

AbstractAbstractThe advent of blue-laser (405nm) optical storage in the form of BD, HD DVD, holographic memories, and UDO would seem to signal the end of optical storage's technology life. But, in fact, the future of optical storage is still very bright. Once theoretical methods of capacity growth, such as multi-layer, multi-level, near-field, and holographic are ready to enter the product mainstream. The engineering challenges of these advanced recording methods on lasers, media, optical pickups, servos, and read/write channels will be significant, but achievable. One can confidently predict the future of optical storage will be 120-130mm disc media with capacities in the 100 GB to 1 TB range.


ContentContentØ Part 1 - IntroductionØ Part 2 - Near term FuturesØ Part 3 - Bleeding Edge FuturesØ Part 4 - Some Enabling ComponentsØ Part 5 - Replication and Disc ManufacturingØ Part 6 - The Bottom lineØ Part 7 - Appendices

Part 1Part 1

Introduction


Common SenseØOptical data storage is subject to

Shannon’s channel capacity law: C = Nxlog2(1+S/N), where N is a function of λand NA and S/N of media quality.

Ø In English, you can’t put 10 lbs of polycarbonate in a 1 lb polyethylene sack.Ø I can’t, and neither can anyone else.


I started research in optical storage at an early age.


The ODS Product Technology Cycle


Optical Storage's Moore's Law

source: Unaxis


Classical Optical Storage Classical Optical Storage -- IIIs the end of the technology line in sight?Is the end of the technology line in sight?

Ø Laser diode (LD) wavelengths (λ) have reached the end of the visible spectrum at 405nm.

Ø Conventional objective lens have reached the limit of usable numerical apertures (NAs).

Ø Spot size is a function of λ/NA; shorter λs and bigger NAs yield smaller spot diameters and higher areal densities.

Ø The technology life appears ended - but wait! This is only true for linear thinking and design.


Classical Optical Storage Classical Optical Storage -- 22Is the end of the technology line in sight?Is the end of the technology line in sight?

Ø For λ fixed at 405nm, classical optical storage can increase capacity in several ways, alone or in combination.

Ø Architecture Examples:– Multilayer Discs (MLD); 2-N surfaces.– MultiLevel Recording (MLR); replicated, phase change.– Near-Field Recording (NFR); read-only and write/read.– Fluorescent Multilayer Disc (FMD); read and record.

Ø Attractive Combinations:– MLD + MLR (25-50 GB/surface x 2.5 ML gain x N surfaces

or 250-500 GB/120mm disc).– NFR + MLR + MLD (50-200 GB/surface x 2.5 ML gain x 1-2

surfaces or 125 GB - 1 TB/120mm disc).

Part 2Part 2

Near Term Futures


Today + 5 years TechnologiesØ Multilayer Recording

– Increases capacity without requiring a corresponding increase in areal density.– 8-layer discs with 200 GB capacity demonstrated by TDK and Philips using Blu-ray layers.– Increases optical media manufacturing and replication complexity significantly.

Ø UDO– 30 GB cartridges shipping today; 60 GB cartridges expected in 2007.– A blue-laser concept, but not Blu-ray (computer application oriented).– Roadmap capacity to 120 GB/cartridge.

Ø Near-field Recording (NFR)– Multiplies effective NA.– Maximizes areal density and surface capacity.– Trades MLD disc manufacturing complexity for optical head-disc interface complexity.

Ø MultiLevel Recording (MLR)– Provides a practical 2.5x multiplier per layer (8 levels).– Can be implemented with a single DSP; not too expensive.– Works with any optical storage recording technology.

Ø 3-D Holographic Memories (Holomems) - Disc Architectures– Deliverable products by end of 2006 after 43 years of R&D.– Mainly professional AV storage, archiving, some general applications.– Only two real players: InPhase Technologies & Optware (Japan).

Ø Fluorescent Multilayer Disc (FMD)– Great concept (discrete layer 3-D storage), but some inherent problems.– Need some heavyweight funding for product development.– Excellent HDTV playback demonstrated for 6-layer disc (red laser).


a) Multilayer Disc


BluBlu--ray Disc Standard Referenceray Disc Standard Reference

Source: Philips


BluBlu--ray Disc Roadmapray Disc Roadmap

Source: TDKSource: TDK


b) UDO


UDO UDO -- The Other BlueThe Other Blue--laser Disclaser Disc

Ø UDO = Ultra Density Optical (a Plasmon plc product)Ø Original design by Sony as successor to 5.25" MO.Ø Designed for computer applications (-R and -RW).Ø 30 GB cartridge media (2-sided phase change disc).Ø ANSI-standard 5.25" MO disc cartridge; jukebox

ready.


Source: Plasmon plc


Source: Plasmon plcMSFB = mean (cartridge) swaps between failures.


c) Near-field Recording


NearNear--Field Recording with VSALsField Recording with VSALs

(source: Lucent Technologies)

λ

NEAR FIELD

Near Fie ld

d / 2

d

Near-Field image of 60 nm marks written by near-field compared with Far-Field

VSAL = Very Small Aperture LaserAperture Size Determines Resolution -- Independent of Laser Wavelength.Exceptionally Small Spot Sizes -- 60nm spots (134Gb/in2) demonstrated in MO material.Beam of any shape demonstrated -- Improves performance & design flexibility.


d) MultiLevel Technology

Ø MultiLevel (ML) is not a product, but a performance-enhancement technology.

Ø Fixed-size data cells support 8 reflection levels (variable areas) on a dye-polymer (-R) or phase change (-RW) recording layer. Yields about 2.5 bits per cell in practice (not the theoretical 3).

Ø The enabler is a proprietary DSP chip (core IC) Ø ML-enhanced drives and media work for CD/DVD

and Blue-laser formats. Should work for all disc formats.

Ø 60GB per 120mm Blue Disc lab demonstrated (Calimetrics, now part of LSI Logic, and Philips research project).


e) Holomems


Holographic Memories (Holomems)Holographic Memories (Holomems)


Holographic Memories Holographic Memories -- HistoryHistoryØ Original concept by P.J. van Heerden (Polaroid) in 1963, based on D. Gabor’s

“wavefront reconstruction” (holography).Ø Generally agreed to be impractical by 1975.Ø Over 50 companies worldwide have invested in and abandoned the technology

(1965-2005).Ø The early 1990s saw a resurgence in interest; for example, DARPA’s

HDSS/PRISM program helped to greatly advanced the art.Ø The “no moving parts” (random access) BORAM model has been abandoned in

favor of the (direct access) optical disc model.Ø Advances in lasers, storage media, photodetector arrays (PDAs), spatial light

modulators (SLMs), hologram stacking methods, data coding, and signal processing have made 300GB 130mm discs feasible today.

Ø Today’s leading companies are InPhase Technologies and Optware (Japan).Ø After more than 40 years of R&D, holographic memories (holomems) appear on

the threshold of commercial viability for a limited set of applications; for example, general archiving and digital video storage. Holomems are not suitable for consumer electronics applications today. However, they can effectively support the creation and delivery processes.


Pros and Cons of HolomemsPros and Cons of HolomemsProsØ Parallel write/read of large data pages (1024 x 1024 pixels common).Ø 3D stacking of holograms in a common volume (increases 2D areal

storage density by a factor of 1,000x, or more).Ø Simple read mechanisms, which reconstruct each data page

independently (ideally, with no crosstalk).

ConsØ Complex system designs.Ø Demanding storage media requirements.Ø Lack of infrastructure (photonic components challenging; optical

communications applications have driven lower pricing, volume, and reliability).

Ø Expensive hardware ($15,000 drives) compared to competing storage technologies (disc media competitive at $120/cartridge).


IBM Demon 2IBM Demon 2Holomem DemonstratorHolomem Demonstrator

source: IBM Almaden Labs


Optware Holomem ProductsOptware Holomem Products

Optware tabletop exhibit at ODS 2004 Optware tabletop exhibit at ODS 2004 (source: ADVENT)(source: ADVENT)


InPhase Technologies PrototypeHolomem Drive and Disc Cartridge

source: InPhase Technologies


InPhase TechnologiesInPhase TechnologiesHolomem Drive SchematicHolomem Drive Schematic

HWP = half wave plate SLM = spatial light modulator HWP = half wave plate SLM = spatial light modulator source: InPhase Technologies source: InPhase Technologies

(record optical path) (read optical path)


InPhase Holomem Recordable Technology "Roadmap"InPhase Holomem Recordable Technology "Roadmap"

1.51.51.5Material Thickness (mm)

407

100

700,000

1696x1710

1200x1200

1st

0.65

1,600

2560 Gb/in2

960 Mbits/s

2010

7050Laser power (mW)

350,000176,000Camera sensitivity (Counts/(J/m2))

1696x17101280x1024PDA Pixels

407407Wavelength (nm)

0.650.65NA of object beam

2nd2ndBragg Null

800300Estimated Capacity (raw GB)

1200x12001280x1024SLM Pixels

12800 Gb/in2

640 Mbits/s480 Gb/in2

160 Mbits/sEffective Areal DensityRaw Data Rate

20082005Specs

Original table from InPhase; edited down by the author - capacity points for 130mm discs added.


source: Maxell


f) Fluorescent Multilayer Disc (FMD)

Ø 5-100 storage layers on a substrate (claimed; about 20 actual)Ø Read signal generated by laser-induced linear or non-linear fluorescenceØ Minimal interaction between layers (adequate signal and SNR)Ø Gives optical storage equivalent HDD multiple discs per spindle capabilityØ No standards issues (works with CD, DVD, and BD/HD DVD media formats)Ø Read Only, Write Once, and ReWritable storage modes are possibleØ Drives are feasible (may need dynamic aberration correction)Ø Disc manufacturing is complex, likely to be expensive initially, but feasibleØ Inventor C3D went out of business, but is back as D Data Inc (New York).

Part 3Part 3Bleeding Edge Futures


Today + 10Today + 10--15 years Technologies15 years TechnologiesØ 3-D Holomems with BORAM (block-oriented random access memory)

ArchitecturesØ UV disc (continuation of the classical optical roadmap - need UV laser

diodes)Ø X-ray disc (digital holography)Ø Atomic/Molecular (data storage by means of configuration or quantum

state)Ø Biological (biorhodopsin and similar; brain simulation)Ø Some enabling means:

– negative refraction (smaller spots, flat lenses)– variable focus lenses– MEMS (e.g., DMM)– nanotech (e.g., self assembly, patterned media)– nanophotonics (e.g., modulators, lasers, gratings)– photonic sieves (for far UV and X-ray spot formation)


Ultraviolet Ultraviolet ““OpticalOptical”” StorageStorageØ Does optical storage end with λ = 405nm?Ø Not if the technology is extended into the near and mid-

range ultraviolet (UV).Ø Diagnosis: UV optical storage will be far more challenging

than near-IR and visible optical storage was.Ø Front surface recording layer and reflection component OPU

(optical pickup unit).Ø Prognosis: within 5 years optical storage at λ = 325nm

(frequency doubled 650nm) will be feasible. The technology will "burn out" before reaching λ = 202.5nm (frequency doubled 405nm).

Ø The trade offs involve a 4x increase in areal density for λ = 202.5nm, versus the complexity and cost of UV components.

Ø Much of UV optical storage technology can/will be adapted from semiconductor lithography.


UV UV ““OpticalOptical”” Storage ChallengesStorage Challenges

Ø UV laser diodesØ UV optical componentsØ UV recording mediaØ Design cost and complexityØ Mastering and replication processesØ Development costsØ Killer application motivation


UV Laser DiodesUV Laser DiodesØ UV laser diode technology is in its infancy.Ø Very few commercial products are available.Ø Nichia is shipping a 20mW CW (100mW pulsed), 375nm product.Ø DPSS (diode-pumped solid state) lasers, which can be

frequency tripled or quadrupled, must be greatly reduced in size and cost to be candidates.

Ø Other options to UV laser diodes and DPSS (for example, KrF or F2) have no possibility of meeting size and cost requirements.

Ø Nanotech may hold the key to long-term prospects.Ø Bottom Line: UV laser diodes are in about the same position

as blue lasers in 1995. Solutions are 3-5 years out.


UV Semiconductor LasersUV Semiconductor Lasers


XX--Ray Ray ““OpticalOptical”” StorageStorageWRITEØ Concept designed for x-radiation with λ < 1nmØ 1D or 2D computer-generated FT HologramsØ Select page size (N or NxN) and offset angleØ Compute and sample analog interference patternØ Apply Data Coding and EDACØ Modulate and Scan Write SpotREADØ Parallel read by means of holographic reconstructionØ Position read beam over hologramØ Project N or N x N pixels onto Photodetector ArrayØ Process and Format Serial Data Stream


XX--Ray Ray ““OpticalOptical”” StorageStorageThe ChallengesØ No compact, safe, inexpensive X-ray laser.Ø All optics must generally be reflective.Ø No compact photodetector arrays.Ø New mastering (write) and replication methods required.The AdvantagesØ No page composer (SLM) required.Ø No 3D media and incoherent superposition (stacking) of

hologram pages required.Ø Can apply method to all media formats (disc, card, or tape).Ø Read servo requirements about the same as today’s DVD.


XX--Ray Ray ““OpticalOptical”” StorageStorage

Performance PotentialØ Assume a disc format; 50 mm diameter

and a recording area of 1600mm2.Ø Areal Density ρ = 1/(2λF#)2

Ø For λ = 0.5nm and F# = 2, ρ = 250Gb/mm2 (160Tb/in2)

Ø C = 50TB (30-40TB user)Ø Access Time = same as DVD-ROM driveØ Read Data Rate = F(# of pixels, read

power, detector sensitivity, scan speed); could achieve 50Gbps.


StateState--ofof--thethe--Art XArt X--Ray LaserRay LaserA FreeA Free--Electron Laser (FEL)Electron Laser (FEL)

Some engineering required to make suitable for optical storage aSome engineering required to make suitable for optical storage applicationspplications

Source: Un. of Hamburg

Part 4Part 4Some Enabling Components


A Few ExamplesA Few Examples

ØNegative RefractionØVariable Focus LensesØGrating Light ValvesØPhoton Sieves


Negative RefractionNegative Refraction

normal refraction

negative refraction



source: Physics Today (December 2003)source: Physics Today (December 2003)

a) negative refraction b) normal (positive) refraction



source: JB Pendry, Imperial College (April 2000)source: JB Pendry, Imperial College (April 2000)


Variable Focus LensesVariable Focus Lenses



source: http://physicsweb.org (Feb 3 2006)source: http://physicsweb.org (Feb 3 2006)

http://physicsweb.org

http://physicsweb.org



source: Photonics Spectra, March 01 , 2005


Grating Light Valve (MOEMS device)Grating Light Valve (MOEMS device)

source: Silicon Light Machines



The minimum finger deflection is 0.002nm; the device dynamic range provides 4096 intensity levels.



Photon SievePhoton SieveA means for focusing UV and XA means for focusing UV and X--ray beams to small spotsray beams to small spots

source: http://www.photonsieve.de/source: http://www.photonsieve.de/

http://www.photonsieve.de/



Photon SievePhoton SieveIntensity profile of the photon sieve is on the left;Intensity profile of the photon sieve is on the left;

its Gaussian counterpart is on the right.its Gaussian counterpart is on the right.

source: http://www.photonsieve.de/http://www.photonsieve.de/



Part 5Part 5Replication and Disc

Manufacturing


Mastering & ReplicationMastering & ReplicationØ The future of optical disc storage will ultimately be determined by disc

mastering and replication processes.Ø Near-UV mastering and modified replication processes already exist and

are proven. Phase transition mastering using a 405nm laser and a highly non-linear photoresist (inorganic) looks promising for BD.

Ø For C > 100GB per layer per 120mm disc, extreme UV or e-beam mastering machines (EBMM) may be required.

Ø EBMM have already achieved 50nm wide pits (DVD uses 300nm); 15nmfeatures are feasible.

Ø Molding processes that preserve the fine structure of the stamping master will be a challenge for ultra-high density optical discs. New molding materials may be needed.

Ø Bonding should be eliminated, if possible; 2P processes should be avoided, if possible.

Ø 100GB (recordable/rewritable) and 200GB (read-only) per layer for 120mm disc have been demonstrated at the research level. TDK and Sharp, for example, have demonstrated 8-layer/25 GB per layer (BD) 200 GB and 2-layer/50 GB per layer (not BD) 100 GB optical disc capacities, respectively. Mastering and replication in a production environment has yet to be demonstrated.


Optical Disc MasteringOptical Disc Mastering-- AFM ImagesAFM Images

(source: Optical Disc Corporation)


This method was developed by Plasmon in the mid-1980s to master its “moth’s eye” write-once optical disc. A simple interferometer (argon laser λ = 488nm) was used. Between exposures, the master disc was rotated by 90 degrees. This also provided an early example of “patterned”media.


Challenges & Opportunities forChallenges & Opportunities forthe Optical Media Industrythe Optical Media Industry

Ø The technology and equipment for CD and DVD is proven and mature. Most of the key problems for BD and HD DVD have been solved. That was the easy part.

Ø Optical media in the next generations will be more complex. Required yield, throughput, and quality will be harder to achieve, regardless of the future technology winner(s).

Ø The cost and complexity of processes and equipment and the unit cost of media will increase, perhaps significantly in some cases. A major challenge to the industry is to prevent or minimize this.

Ø New or modified processes, manufacturing equipment, and quality control methods will be required for MLD, holographic, and NFR media.

Ø More sophisticated and complex in-line and off-line test and measurement equipments will be required.

Ø The cost of R&D will increase significantly; expect to hire more materials scientists, chemists, and physicists.

Ø On the positive side, new opportunities are plentiful, and provide a natural evolutionary path. On the negative side, a finite probability exists that increasing the capacity optical storage media may well become too expensive (diminishing economic returns).

Part 6Part 6

The Bottom Line


Summary and ConclusionsSummary and ConclusionsØ Existing optical storage technologies still have at least a 10-year useful

product life cycle. However, classical optical storage will have reached the end of its technology life by then.

Ø Future products will primarily be the blue-disc progeny of Blu-ray Disc.Ø Optical storage 5-10 years from today will be provided mainly by evolved

versions of today’s proven technologies.Ø Over the 10 year horizon, optical storage will likely be provided by a

mixture of today’s evolving and future technologies. Displacement technologies cannot be ruled out.

Ø Optical storage will continue to dominate the removable-media AV applications sector in consumer electronics. "HDTV" playback and recording and personal storage applications will be the dominantapplications.

Ø Optical storage 10+ years from today will likely be provided by a mixture of today’s evolving and future technologies.

Bottom Line: Although facing many challenges and competitors, the future of optical storage for the next 10 years is still very bright.


A RecommendationA RecommendationThe Media-Tech Association should form a standing committee of members and selected non-members to:

1) Create an optical storage roadmap to track the evolution of optical storage and related technologies and components, as they relate to optical media manufacturing and replication.

2) Publish an annual report on key findings.3) Review the key results at the annual Frankfurt and

Long Beach meetings.

Part 7Part 7

Appendices


< Appendix A >< Appendix A >ReferencesReferences

1) "Challenges and Opportunities of Optical Recording," Dr. Di Chen, Chen & Associates, Proc. Of SPIE, Vol. 5966, September 15, 2005.

2) "Relevant Technologies for Future Generations of Optical Data Storage," Prof. M. Mansuripur (Optical Sciences Center, Un. of Arizona), Media-Tech Conference, Hollywood, CA, August 31, 2004.

3) "Optical Recording at 1 Tb/in2," Prof. T. D. Milster, (Optical Sciences Center, Un. of Arizona), THIC Meeting, Louisville, CO, July 22-23, 2003.

Some of Dick Zech's papers:Ø “Volume Hologram Optical Memories: Mass Storage Future Perfect?,” Optics and

Photonics News, August 1992, pp. 16-25.Ø “Where do we go from here? Digital Media Futures for Consumer Electronics,”

Diskcon 2002, September 17-19, 2002, San Jose, CA.Ø “UV Futures for Optical Disc (What’s Next for DVD after Blu-ray?),” adapted from

the International Storage Industry Consortium (INSIC) 2003 Conference on the Future of Optical Data Storage, San Francisco, CA, January 23-25, 2003.

Ø “Technology Analysis: Optical Storage Futures - The Consumer Electronics Perspective," IIST Workshop XVII, Asilomar Conference on Computer Storage, Monterrey, CA, December 2003.

Ø The 2005-15 Roadmap: Optical Storage for Consumer Electronics," An ADVENTSpecial Report, December 2004.

Copies in PDF format available upon request by e-mail to [email protected].

mailto:[email protected]


< Appendix B >< Appendix B >About the AuthorAbout the Author

Dr. Dick Zech has nearly 40 years of computer storage and photonics experience. His academic focus was on modern optics, electromagnetic theory, communications theory, advanced mathematics, and the chemistry/physics of optical materials. His doctoral dissertation was entitled "Data Storage in Volume Holograms (supervised by Prof. Emmett N. Leith at the University of Michigan). His primary expertise is in the fields of optical data storage, holography, recording media, and optical disc replication processes and technology. His main interests are data storage; lasers; materials physics, chemistry and processes; control and positioning of light beams; and photonic components and their integration into fully functional information processing systems. Much of Dick’s early work (1965-1979) was for the US Department of Defense, NASA and various intelligence agencies. The primary goal of this work was to use photonics technology for the rapid acquisition, processing, storage and communication of data vital to national defense and the space program (including holographic wideband recorders and BORAM holographic memories) . In addition, Dick also has significant engineering, product and business development, and sales and marketing management experience, which he has used as a consultant for the past 18 years. Since 1990 he has worked as an expert witness in numerous patent infringement litigations (and a few involving breach of contract and theft of trade secrets) and evaluated over 200 patents for technical and economic merit. Among his inventions are the projected real-image Lippmann-Bragg hologram, volume manufacturing methods for holograms, and the multi-channel optical disc recorder (DIGIMEM). He has published over 150 papers, reports, and presentations.

the future direction of optical data storage

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