Optikai adattárolás ma és holnap(után)titan.physx.u-szeged.hu/~optisk/Koppa.pdf · Optikai adattárolás ma és holnap(után) Koppa Pál Technical University of Budapest Department

Optikai adattárolás ma és

holnap(után)

Koppa Pál

Technical University of Budapest

Department of Atomic Physics

www.fat.bme.hu

Koppa Pál: Optikai adattárolás, "Sokszínű Optika" nyári iskola 2011, Szeged 2

Tartalom

I. A mai optikai adattárolók

II. Az adatsűrűség

III. Térfogati adattárolás

IV. Holografikus adattárolás

V. Optikai adattárolás a Műegyetemen

VI. Fázisban modulált adatlapok

VII. Mikroholografikus rendszer

VIII. Konklúzió


I. Egy mai optikai adattároló felépítése


Mi van a lemezen?

CD, DVD, BLU-Ray –ROM:

Pit & land interference

CD, DVD, BLU-Ray –R:

Organic dye with permanent

absorption change


Újraírható lemez CD, DVD, BLU-Ray +/–RW: Metal alloy with reversible phase change


A tárolási kapacitás fejlődése

Tegnap Ma Holnap És holnapután???

650 MB 4.7 GB 25 GB


II. Az adatsűrűség

22

6,0

)sin(

6,0

nNADDAdatsűrűség:

)sin( nNA


NA növelése? Elvileg lehetséges

közeltéri (near-field) technikák:

•SIL (szilárd immerziós lencse)

•Elhaló hullám becsatolás (evanescent wave)

csökkentése? •UV lézer dióda elvileg lehetséges…

Diffrakciós limit áthágása ??? •Miért ne?

•Ld. superresolution


Írás túl a diffrakciós határon - egy példa

Magneto-optical crescent recording

Switching

Threshold

H

Temperature

Profile Laser Beam

Small Crescent Domains

H

Media

Motion


Olvasás

Readout Layer

Recording Layer

Temp Profile

Side View Top View

In Plane

Mask Thermal

Aperture

Magnetic Super Resolution (MSR)

Center Aperture Detection (CAD)

Solves the Diffraction Limit Problem!

However: Low signal levels


A 2D adatsűrűség nagyságrendi növelése nem kézenfekvő !

Megoldás???

Térfogati tárolás


III. Térfogati tárolás

Maximális adatsűrűség:

Er( )2

max Er( )2

Er ()2

maxEr ()2

3

422NA5.5NA2

6,0

NADD

x,y z

3D adatsűrűség elvi határa:

~14 bit/mm3 térfogati adatsűrűség (NA=0.85, l=400nm)

~12 000 Gbit/inch2 felületi adatsűrűség

~25 TB/lemez felhasználói kapacitás (R=125mm, t=1mm, CR=0.6)


CD „térfogatosítása”

2,4 rétegű Blu-ray lemez kapható

8, 16 réteg fejlesztés alatt (200-400 GB)

Abszorpció, transzmisszió, szórás

→ SNR csökken

Komplex és drága lemez-technológia


2 fotonos térfogati tárolás


Arany nanorudak, plazmonrezonancia


IV. Holografikus adattárolás


Multiplexelés

Szög multiplexelés

(síkhullám referencia)

Shift multiplexelés

(gömbhullám referencia) Hullámhossz multiplexelés

(síkhullám referencia)

Fázis-kódolt multiplexelés

(N síkhullám szuperpozíciója)


Holografikus tároló-anyagok

Vastagság →

Dinamika tartomány →

Érzékenység →

Optikai minőség →

Zsugorodás, hőtágulás →

MUX száma

Diffrakciós hatásfok

Írási sebesség

Jel-zaj viszony

Jel-zaj viszony

2#

M

M

)sin(L2 s

r

Tipikus anyagok: fotorefraktív kristályok, fotopolimerek


InPhase Technologies

Hologram felvétel


InPhase Technologies

Hologram kiolvasás


„Piacon kapható” holografikus adattároló

Drive

•300GB capacity; •20MB/s, 160 Mb/s transfer rate •WORM recording format

•405 nm laser wavelength

Media

•1.5 mm recording material •130 mm diameter disk •50 year archive life


„Kollineáris” rendszer

Optikai rendszer

Adatlap


Mikroholografikus rendszer

n

FES / TES

FES / TES se

rvo

sy

ste

m

data control

laser

multiplex

objective

lens

actuator

actuator

reflector

astigmatic

lens

astigmatic

lens

quad

quad

collimator

beam

splitter

beam

splitter

detector

Confocal

filter

Setup with confocal filtering


Az adatsűrűség fejlődése

Seagate HDD 2005 (421 Gb/inch2)

Samsung HDD 2011 (739 Gb/inch2)

microSDXC 2011 (2000 Gb/inch2)

8 rétegű Blu-ray 2007 (100 Gb/inch2)

Holographic (InPhase) 2006 (500 Gb/inch2)


V. Optikai adattárolás a Műegyetemen

CD and MO technology (1988-’91 in

cooperation with VIDEOTON)

Page oriented optical memory card

(1995’98 with Optilink AB)

Holographic data storage (from 1998 with Optilink and Bayer Innovations)

2 Photon volume optical data storage (1999 with EOARD, Univ. of Buffalo)

Communication compatible all optical data

storage (2001 with Deutsche Telecom)

Technical support on CD/DVD RW manufacturing (from 2000 with Philips Hungary)

High density holographic storage (ATHOS

and MICROHOLAS from 2004)


Holographic Memory Card Demonstrator Systems

R/W unit

power supply Read-only unit

Portable Holographic Storage Demonstrator Systems

Read only and read&write units demonstrated

Inherently secure data storage technology

2.77 bits/mm2 (1012 bit/cm3) data density


Polarizációs holográfia

Key features No -1 and higher diffracted orders

High diffraction efficiency possible

Requires photoanisotropic storage material

Reference beam

Storage material

Interference pattern (hologram)

Circular polarization

Linear polarization


Read & Write System Optical Set-up

Green laser

source Beam splitter

Mirror Mirror

(aperture stop, Fourier filter)

Object SLM (transmissive)

CCD array

Memory card Storage layer

λ/4 plate #2

Fourier objective #2

Polarisation beam splitter with central hole in the

splitting layer

Polarisation filter

Fourier objective #1

Mirror

λ/4 plate

Fourier lens

Random-phase mask

Polarisation beam splitter

Beam expander Beam shaper

Beam shaper

Beam contractor

Aperture stop of reference arm

Mirror 8f Fourier module

Signal beam

Reference beam

Read&Write head


Elements of the system


Reconstructed Data Page

•Constant weight sparse code modulation, 3x oversampling at CCD

•16.4 Kbyte in a hologram, 2.77 bits/mm2 (1012 bits/cm3 ) storage density

• raw symbol error rate: 10-4, user bit error rate after RS error correction: 10-12


0 π π 0

π 0 0 π

0 π π 0

π 0 0 π

π 0 π π

0 0 π 0

π π 0 0

0 0 π π

π 0 π π

0 0 π 0

π π 0 0

0 0 π π

Input data FT of data Ref. wave

Rec. wave Recording

FT

FT

FT

Reconstruction

Output

Correct code

Different code

Holographic Cryptography with phase coded reference wave


Reconstructed holograms

Recording reference =

Reconstructing reference

Recording reference

Reconstructing reference


Object plane encoding

Laser

Amplitude

SLM Phase mask Aperture

Data recovery

and ECC CCD Hologram

Reference beam

Object beam Reconstructed beam

Data encoding

PBS

Phase SLM

Does not make any encoding for amplitude images !!!

Phase modulated data page is needed !!

Phase SLM


VI. Fázisban modulált adatlapok

Laser

Amplitude

SLM Phase mask Aperture Data recovery

and ECC CCD Hologram

Reference beam

Object beam Reconstructed beam

Data encoding

PBS

Phase SLM

Phase modulated data page:

+Simple object arm

+Smooth Fourier plane

+Higher object power

Phase SLM

-Difficult data recovery


Phase to amplitude conversion Phase object electric field Phase object shifted Superimposed phase objects

1 -1 1 -1 -1 1 -1 1 0 0 0 0 0 0 0 0 1 -1 1 -1 -1 1 -1 1 0

-1 1 -1 1 1 -1 1 -1 0 1 -1 1 -1 -1 1 -1 1 -1 2 -2 2 0 -2 2 -2 1

-1 1 1 1 -1 -1 -1 1 0 -1 1 -1 1 1 -1 1 -1 -1 0 2 0 0 0 -2 2 -1

1 -1 1 -1 1 1 1 -1 0 -1 1 1 1 -1 -1 -1 1 1 -2 2 0 2 0 0 -2 1

-1 -1 1 1 -1 -1 -1 -1 + 0 1 -1 1 -1 1 -1 1 -1 = -1 0 0 2 -2 0 -2 0 -1

1 -1 -1 1 1 1 1 -1 0 -1 -1 1 1 -1 1 -1 -1 1 -2 -2 2 2 0 2 -2 -1

-1 1 1 1 -1 -1 -1 1 0 1 -1 -1 1 -1 1 1 -1 -1 2 0 0 0 -2 0 2 -1

-1 1 1 -1 1 -1 1 -1 0 -1 1 1 1 -1 -1 -1 1 -1 0 2 0 2 -2 0 -2 1

-1 1 1 -1 1 -1 1 -1 0 -1 1 1 -1 1 -1 1 -1

Phase object intensity Shifted intensity Intensity of superimposed phase objects

1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0

1 1 1 1 1 1 1 1 0 1 1 1 1 1 1 1 1 1 4 4 4 0 4 4 4 1

1 1 1 1 1 1 1 1 0 1 1 1 1 1 1 1 1 1 0 4 0 0 0 4 4 1

1 1 1 1 1 1 1 1 0 1 1 1 1 1 1 1 1 1 4 4 0 4 0 0 4 1

1 1 1 1 1 1 1 1 0 1 1 1 1 1 1 1 1 → 1 0 0 4 4 0 4 0 1

1 1 1 1 1 1 1 1 0 1 1 1 1 1 1 1 1 1 4 4 4 4 0 4 4 1

1 1 1 1 1 1 1 1 0 1 1 1 1 1 1 1 1 1 4 0 0 0 4 0 4 1

1 1 1 1 1 1 1 1 0 1 1 1 1 1 1 1 1 1 0 4 0 4 4 0 4 1

0 1 1 1 1 1 1 1 1 0 1 1 1 1 1 1 1 1


Optical implementation

BIS CCDP45°

E

OCirc.

Thickness t=6,2

mm

Opical axis

=12

d

Clear aperture d25 mm

LTB (Li2B4O7)

Image duplication and shift by:

•Birefringent plate

•Diffraction grating

•Etc.


Experimental results

0

500

1000

1500

2000

2500

3000

0 25 50 75 100 125 150 175 200

CCD Grey level (0..255)

No

. o

f o

ccu

ren

ces

-12

-10

-8

-6

-4

-2

0

0 25 50 75 100 125 150

Fourier filtering [%]

Lo

g10(B

ER

)

Experiment

Simulation

Simulation

Experiment


Tolerances

I n terf erence

maxIn terf erence( )25 5

-60

-40

-20

0

20

40

60

80

100

120

3 4 5 6 7 8 9 10 11

Hologram misalignment (% of hologram size)

His

tog

ram

sp

ac

ing

0.0001

0.001

0.01

0.1

1

0 5 10 15 20 25

Image phase SLM Shift (microns)

BE

R


Ref

Obj

SLM 1 FT lens

SLM 2

Hologram FT lens SLM 3 BIS CCD

/2

Recording Ref Reconstruction

Encrypted storage


Encrypted storage

Histogram

0

100

200

300

400

500

0 50 100 150 200 250 300

CCD grey level (0..255)

No

. O

f o

ccu

ran

ces


Object plane phase code

0

100

200

300

400

500

0 50 100 150 200 250 300


No

. O

f o

cc

ura

nc

es

Total histogram

Logical 1-s

Logical 0-s


Fourier plane phase code

0

100

200

300

400

500

0 50 100 150 200 250 300


No

. O

f o

cc

ura

nc

es

Total histogram

Logical 1-s

Logical 0-s


Dual phase code

0

100

200

300

400

500

0 50 100 150 200 250 300


No

. O

f o

cc

ura

nc

es

Total histogram

Logical 1-s

Logical 0-s


n

FES / TES

FES / TES se

rvo

sy

ste

m

data control

laser

multiplex

objective

lens

actuator

actuator

reflector

astigmatic

lens

astigmatic

lens

quad

quad

collimator

beam

splitter

beam

splitter

detector

Confocal

filter

Setup with confocal filtering

VII. Mikroholografikus rendszer


The system model

1. Laser diode

2. Collimator lens

3. Objective lens + aperture

4. Disk

5. Microholograms in the disk

6. Confocal filter

1. Calculate scattering (4) → diffracted field

2. Propagate to lens (3) → far field wave

3. Add spherical phase (3) → perfect lens

4. Cut wave by aperture (3) → truncated Gauss

5. FFT of wave (2) → beam focused on

pinhole

6. Cut wave by pinhole (6) → confocal filtering


Bragg diffraction calculations

l

l

r

r

r

r

zzyyxxik

pd dxdydzzzyyxx

ezyxnzzyyxxE

kzyxzyxE

2

1

2

1

2

1

)()()(2

111

)()()(),,(),,(

4),,,,,(

21

21

21

•Volume scattering on weak index modulation

•Volume integral using the first Born approximation

•Both scalar and vector form can be integrated numerically

Diffracted field Probe wave Index modulation Green function

CCzyxEzyxEzyxn sr ),,(),,(),,(

)()(2)(

0

22

2

22

)(

2),,(

ziikzzR

yxik

zw

yx

eezw

EzyxE

Linear material:

Gaussian writing and

reading beams:


Intensity distribution at output

Confocal filter

aperture size

dz=0

dy=0

dz=6 mm

dy=.5mm


First model results

Diffracted intensity at z=100 microns Index modulation of a microhologram

Transversal scan 532nm

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

-3 -2 -1 0 1 2 3

shift (micron)

FFT Bornapproximation

Measurement

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

-15 -10 -5 0 5 10 15

z [micrometer]

Energy

[a.u.]

Measurement

FFT Born appr.

Volume integral

Longitudinal scan

532nm


Statistical evaluation

0.4mm

Hologram pitch

Random hologram configurations

50% white rate

Track pitch: 0.7μm

Hologram pitch : 0.4 μm Layer pitch : 6 μm

Modeling up to 7 layers.

Histograms of 10 000 configurations

Reconstructed hologram

Two nearest neighbors

Holograms in the same layer

Holograms in other layers

0.7mm

Track pitch


Bit error rate calculation

c

c

E

E

dEEWdEEWN

BER0

01 )()(1

Ec

W1(E) W0(E)

W0 & W1: fitted probability distributions

Ec: read energy at crossing point

N: No of bits in the histogram


Non-local saturation

•Exposure → photo-polymerisation → relaxation by monomer diffusion

•Sensitivity to next exposure proportional to monomer concentration

•Diffusion is to be taken into account!

•Calculation of polymer and monomer cc. as a function of time and space

Result: non-linear, non-local material model

Diffusion equation:

Monomer concentration

Light induced polymerization rate

Non-local material response

Diffusion constant

Change of monomer concentration

Grad of mon. cc

* J. R. Lawrence, F. T. O'Neill, J. T. Sheridan, Adjusted intensity nonlocal diffusion model of

photopolymer grating formation, J. Opt. Soc. Am. B, Vol. 19, No. 4, Page 621-629, (April 2002)

'),'(),'()',(

),(),(

),(dxtxutxFxxR

x

txutxD

xt

txu


Diffusion model results

If Texp<< Tdiff and Iexp<< Isat

Diffusion can be modeled with

Gaussian smoothing of monomer

concentration!

If Texp Tdiff

Saturation and possible fringe distortion

Non-local response

Provides the known CGS curve and M#


Holograms with non-local model

Unequal diffraction efficiencies

Non-local response

Good fit to experimental scans


VIII. Konklúzió

Követelmények:

-Nagy adatsűrűség, nagy adatátviteli sebesség

-Hosszú archíválási idő

-Biztonság

-Könnyű kereshetőség -Olcsó adathordozó, nem nagyon drága meghajtó

Holographic?

2 photon 3D?

5D?

????

>1000GB

(200 x DVD)

?

Optikai adattárolás ma és holnap(után)titan.physx.u-szeged.hu/~optisk/Koppa.pdf · Optikai adattárolás ma és holnap(után) Koppa Pál Technical University of Budapest Department

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