Optikai adattárolás ma és holnap(után)

Optikai adattárolás ma és holnap(után) Koppa Pál

Technical University of Budapest Department of Atomic Physics www.fat.bme.hu

Tartalom I. II. III.

IV. V. VI. VII. VIII.

2

A mai optikai adattárolók Az adatsűrűség Térfogati adattárolás Holografikus adattárolás Optikai adattárolás a Műegyetemen Fázisban modulált adatlapok Mikroholografikus rendszer Konklúzió

Koppa Pál: Optikai adattárolás,

"Sokszínű Optika" nyári iskola 2011, Szeged

I. Egy mai optikai adattároló felépítése

3



Mi van a lemezen?

CD, DVD, BLU-Ray –ROM: Pit & land interference

4


CD, DVD, BLU-Ray –R: Organic dye with permanent absorption change


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

5



A tárolási kapacitás fejlődése

6

Tegnap

Ma

Holnap

650 MB

4.7 GB

25 GB


És holnapután???


II. Az adatsűrűség

NA  n  sin()



2

 NA   n  sin()  Adatsűrűség: DD      0,6     0,6     

7


2


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

8



Írás túl a diffrakciós határon - egy példa 

Magneto-optical crescent recording

Laser Beam

Temperature Profile

Small Crescent Domains

Switching Threshold

H Media Motion H

9



Olvasás    

Magnetic Super Resolution (MSR) Center Aperture Detection (CAD) Solves the Diffraction Limit Problem! However: Low signal levels Thermal Aperture

Temp Profile

In Plane Mask

Readout Layer Recording Layer

Side View 10


Top View "Sokszínű Optika" nyári iskola 2011, Szeged

A 2D adatsűrűség nagyságrendi növelése nem kézenfekvő !

Megoldás???

Térfogati tárolás

11



III. Térfogati tárolás 3D adatsűrűség elvi határa:

x,y

z

   2

2

)rE( Er ()    

Maximális adatsűrűség:

 NA  DD     0,6   

2  2 rE (x(aEr m)   )max

2

 2 NA2  5.5 NA4    3      

~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) 12



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 

13



2 fotonos térfogati tárolás

14



Arany nanorudak, plazmonrezonancia

15



IV. Holografikus adattárolás

16



Multiplexelés

Szög multiplexelés (síkhullám referencia)

Hullámhossz multiplexelés (síkhullám referencia)

17


Fázis-kódolt multiplexelés (N síkhullám szuperpozíciója)

Shift multiplexelés (gömbhullám referencia) "Sokszínű Optika" nyári iskola 2011, Szeged

Holografikus tároló-anyagok



Vastagság



Dinamika tartomány



Érzékenység Optikai minőség

 

→ MUX száma

 r 

→ Diffrakciós hatásfok

 2L  sin(s )

M #   M 

→ Írási sebesség → Jel-zaj viszony Zsugorodás, hőtágulás → Jel-zaj viszony

Tipikus anyagok: fotorefraktív kristályok, fotopolimerek 18



2

InPhase Technologies

Hologram felvétel

19



InPhase Technologies

Hologram kiolvasás

20



„Piacon kapható” holografikus adattároló

Drive •300GB capacity; •20MB/s, 160 Mb/s transfer rate •WORM recording format •405 nm laser wavelength

21

Media •1.5 mm recording material •130 mm diameter disk •50 year archive life Koppa Pál: Optikai adattárolás,


„Kollineáris” rendszer

Adatlap

Optikai rendszer

22



Mikroholografikus rendszer data control   

laser

n

detector

multiplex collimator

Confocal filter

beam splitter

beam splitter astigmatic lens

objective lens

FES / TES actuator

reflector

FES / TES

servo system

quad

actuator astigmatic lens

quad

Setup with confocal filtering

23



Az adatsűrűség fejlődése

Seagate HDD 2005 (421 Gb/inch 2)

8 rétegű Blu-ray 2007 (100 Gb/inch 2)

Samsung HDD 2011 (739 Gb/inch 2)

Holographic (InPhase) 2006 (500 Gb/inch 2)

microSDXC 2011 (2000 Gb/inch2)

24



V. Optikai adattárolás a Műegyetemen      



25

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    

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

R/W unit

power supply

26


Read-only unit


Polarizációs holográfia Interference pattern (hologram)

Reference beam

Circular polarization

Storage material

Linear polarization

Key features   

27

No -1 and higher diffracted orders High diffraction efficiency possible Requires photoanisotropic storage material



Read & Write System Optical Set-up Beam expander

Green laser source

Beam splitter

Object SLM (transmissive)

Mirror Fourier objective Beam shaper (aperture stop, #1 Fourier filter)

Mirror λ/4 plate Fourier lens Beam contractor

Reference beam Mirror

Signal beam

Aperture stop of reference arm

Read&Write head

Random-phase mask CCD array Polarisation filter λ/4 plate #2

Beam shaper

28

Mirror

8f Fourier module

Polarisation Polarisation beam splitter Fourier objective #2 beam splitter with central hole in the splitting layer


Storage layer

Memory card


Elements of the system

29



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 30



Holographic Cryptography with phase coded reference wave Reconstruction Rec. wave

Recording Input data

FT of data FT

Ref. wave 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

Output FT

Correct code

0

π

π

0

π

0

0

π

0

π

π

0

π

0

0

π

FT

Different code 31



Reconstructed holograms

32



Recording reference =

Recording reference

Reconstructing reference

Reconstructing reference



Object plane encoding Reference beam Laser

PBS

Phase SLM

Data encoding

Amplitude SLM

Aperture Phase Phasemask SLM

Hologram CCD

Data recovery and ECC

Reconstructed beam

Object beam

Does not make any encoding for amplitude images !!! Phase modulated data page is needed !!

33



VI. Fázisban modulált adatlapok Reference beam

Laser

PBS

Phase SLM

Amplitude SLM

Aperture Phase mask SLM

Hologram CCD Data recovery and ECC

Data encoding

Object beam

Phase modulated data page: +Simple object arm +Smooth Fourier plane +Higher object power 34


Reconstructed beam

-Difficult data recovery


Phase to amplitude conversion Phase object electric field

Phase object shifted

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

1

1

1

-1

-1

-1

1

0

-1

1

-1

1

1

-1

1

-1

1

-1

1

1

1

-1

0

-1

1

1

1

-1

-1

-1

1

1

-1

-1

-1

-1

0

1

-1

1

-1

1

-1

-1

1

1

1

1

-1

0

-1

-1

1

-1

1

1

1

-1

-1

-1

1

0

1

-1

-1

1

1

-1

1

-1

1

-1

0

-1 -1

+

Phase object intensity

35

Superimposed phase objects

1

-1

1

-1

-1

1

-1

1

0

1

-1

2

-2

2

0

-2

2

-2

1

1

-1

-1

0

2

0

0

0

-2

2

-1

-1

-1

1

1

-2

2

0

2

0

0

-2

1

1

-1

1

-1

-1

0

0

2

-2

0

-2

0

-1

1

-1

1

-1

-1

1

-2

-2

2

2

0

2

-2

-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

2

0

2

-2

0

-2

1

1

1

-1

1

-1

1

-1

0

-1

1

1

-1

1

-1

1

-1

=

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 E O

Circ.

Image duplication and shift by: •Birefringent plate •Diffraction grating •Etc.

BIS

P45°

CCD

Opical axis



=12 

Clear aperture d25 mm

d Thickness t=6,2 mm

LTB (Li 2B4O7)

36



Experimental results Simulation

3000

0

2500

-2

1500 1000 500

-4 -6 -8 -10

0

-12

0

25

50

75

100

125

150

CCD Grey level (0..255)

37

Experiment Simulation

2000

Log10(BER)

No. of occurences

Experiment


175

200

0

25

50

75

100

125

150

Fourier filtering [%]


Tolerances 1 0

5

10

15

20

25

BER

0.1

0.01

0.001

0.0001

Image phase SLM Shift (microns)

120

Histogram spacing

100 80 60 40 20 0 3

4

5

6

7

8

9

10

-20 -40 -60

Hologram misalignment (% of hologram size)

38



11

Encrypted storage /2

Ref

Recording Reconstruction SLM 2

Obj

SLM 1

39


FT lens

Hologram

FT lens

SLM 3 BIS CCD


Encrypted storage

Histogram 500

No. Of occurances

400

300

200

100

0 0

50

100

150

200

250

300

CCD grey level (0..255)

40



Object plane phase code

500

No. Of occurances

400

Total histogram Logical 1-s Logical 0-s

300

200

100

0 0

50

100

150

200

250

300


41



Fourier plane phase code

500

400

No. Of occurances


300

200

100

0 0

50

100

150

200

250

300


42



Dual phase code

500

No. Of occurances

400


300

200

100

0 0

50

100

150

200

250

300


43



VII. Mikroholografikus rendszer data control   

laser

n

detector

multiplex collimator

Confocal filter

beam splitter

beam splitter astigmatic lens

objective lens

FES / TES actuator

reflector

FES / TES

servo system

quad

actuator astigmatic lens

quad

Setup with confocal filtering 44



The system model 1. Laser diode 2. Collimator lens 3. Objective lens + aperture 4. Disk 5. Microholograms in the disk 6. Confocal filter

1. 2. 3. 4. 5.

Calculate scattering (4) Propagate to lens (3) Add spherical phase (3) Cut wave by aperture (3) FFT of wave (2) pinhole 6. Cut wave by pinhole (6)

45


→ diffracted field → far field wave → perfect lens → truncated Gauss → beam focused on

→ confocal filtering


Bragg diffraction calculations •Volume scattering on weak index modulation •Volume integral using the first Born approximation •Both scalar and vector form can be integrated numerically ik ( x  x ) 2 ( y  y ) 2 ( z  z ) 2

l r r

1 1 k2 e 1 Ed ( x1 , y1 , z1 ,x,y,z )   E p ( x  x, y  y, z  z )n( x, y, z ) dxdydz 2 2 2 4  ( x  x )  ( y  y )  ( z  z ) l rr 1 1 1

Diffracted field

Probe wave

Linear material: Gaussian writing and reading beams:

46


Index modulation

Green function

n( x, y, z)  Er ( x, y, z)Es ( x, y, z)  CC

E ( x, y, z )  E0 

2 e  w( z )



x2  y2 w( z ) 2

ik

e

x2  y2 ikz i ( z ) 2R( z)


Intensity distribution at output

dz=0 dy=0

Confocal filter aperture size

dz=6 mm dy=.5mm

47



First model results

Index modulation of a microhologram

Transversal scan 532nm

Longitudinal scan 532nm

1

Energy 0.9 [a.u.]

Measurement FFT Born appr. Volume integral

0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0

-15

-10

-5

0

5

Diffracted intensity at z=100 microns

10

15

1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0

FFT Born approximation Measurement

-3

-2

-1

0

1

2

shift (micron) z [micrometer]

48



3

Statistical evaluation Random hologram configurations

0.4mm Hologram pitch

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

0.7mm Track pitch

Reconstructed hologram Two nearest neighbors Holograms in the same layer Holograms in other layers 49



Bit error rate calculation W0(E)

W1(E)

Ec W0 & W1: fitted probability distributions Ec: read energy at crossing point N: No of bits in the histogram Ec    1 BER  W1 ( E )dE   W0 ( E )dE    N  0 Ec 

50



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: 

u ( x, t )   u ( x, t )    D( x, t )   R( x, x' )  F ( x' , t )u ( x' , t )dx'  t x  x   Grad of mon. cc Diffusion constant Change of monomer concentration

51


Monomer concentration Light induced polymerization rate Non-local material response

* 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)


Diffusion model results

If Texp Tdiff Saturation and possible fringe distortion Non-local response Provides the known CGS curve and M#

52


If Texp<< Tdiff and Iexp<< Isat Diffusion can be modeled with Gaussian smoothing of monomer concentration! "Sokszínű Optika" nyári iskola 2011, Szeged

Holograms with non-local model

Unequal diffraction efficiencies Non-local response Good fit to experimental scans

53



VIII.

Konklúzió

Holographic? 2 photon 3D? 5D? ????

? >1000GB (200 x DVD)

Követelmények: -Nagy adatsűrűség, nagy adatátviteli sebesség -Hosszú archíválási idő -Biztonság -Könnyű kereshetőség -Olcsó adathordozó, nem nagyon drága meghajtó 54



Optikai adattárolás ma és holnap(után)

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