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POLICRYPS structures: Self-aligning liquid crystal electro-optic constructs Luciano De Sio Beam Engineering for Advanced Measurements Company, 1300 Lee Road, Orlando, Florida 32789, USA.

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Outline  DIFFRACTION GRATINGS

 HOLOGRAPHIC SETUP: HIGH STABILITY LEVEL

 POLICRYPS: THE RECIPE

 POLICRYPS: OPTICAL AND ELECTRO - OPTICAL PROPERTIES

 POLICRYPS: SELF ALIGNING LIQUID CRYSTALS

 CONCLUSION

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Diffraction Gratings A diffraction grating is an optical component with a periodic structure, which splits and diffracts light into several beams travelling in different directions.

Fabrication processes • Photolithography • Electron-beam lithography • Interference holography

Pro and Cons • Large area – low resolution • High resolution – Expensive, small area • Large area, easy method - Instability

Diffraction Gratings: lack of tunability/switching severely limits the applications [email protected]

Y Axis Title

Holographic Polymerization 6

Multiple light beam interference + photosensitive materials 4

2

0 -10

0

10

20

30

X Axis Title

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40

50

60

Liquid Crystals Soft matter is a subfield of condensed matter comprising a variety of physical states that are easily deformed

by thermal stresses or thermal fluctuations. They include liquids, colloids, biological materials and Liquid Crystals The fourth state of matter

• Long range order • Broad band range of birifringence • High sensitivity to AC, DC and Optical field

Liquid Crystals Phases [email protected]

Holographic Polymer Dispersed Liquid Crystals (H-PDLC) Holographic photopolymerization

Bunning et al. (2000), Annual Review of Material Science 30, 83

Drawbacks • Scattering • High switching voltage Pavani, K. et al. (2009). Journal of Optics A: Pure and Applied Optics

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University of Calabria POlymer LIquid CRYstal Polymer Slides

R. Caputo, L. De Sio, A. Sukhov, A. Veltri, C.Umeton Development of a new kind of holographic grating made of liquid crystal films separated by slices of polymeric material Optics letters 2004, 29,1261

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Y Axis Title

6

Stability problems during curing Unstable setup Stable setup

4

2

0 -10

0

10

20

30

X Axis Title

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40

50

60

Y Axis Title

8

Stability problems during curing

6

Unstable setup

Irregular morphology

4 High switching voltages

High response time 2

Possible solutions 0

Passive setup -10 0

10

PD 1

PD 2

20

30

40

PD2

X Axis Title

PD1 S

S

VPD

PD3 Ar+ Laser

M P l/2

PD 3

Piezo-Mirror

P

l/2 BE

M BE

BS

2qcu r

M

2qcur

Ar+ Laser

Active setup 50 60

BS THORLABS

PID system

X-AXIS

150.0 V EXT

INT

3-AXIS PIEZO CO NTRO LLER MO DEL MDT693 Y-AXIS

150.0 V EXT

INT

Z-AXIS

EXT

INT

150.0 V EXT

INT

ENABLE PO WER

VPS

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MASTER SCAN

Passive setup 30 20 10

exp(deg)

0 -10

without stabilization

-20 -30 -40 -50 -60 0

100

200

300

400

500

600

700

800

900 1000

30

time (sec.)

20

with stabilization

exp(deg)

10 0 -10 -20 -30 0

200

400

600

time(sec)

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800

1000

Active setup PD2 PD1

S

VPD 2qcur

M PD3 Ar+ Laser

Piezo-Mirror

P l/2

BE

BS THORLABS

PID system

X-AXIS

VPS

150.0 V EXT

INT

3-AXIS PIEZO CO NTRO LLER MO DEL MDT693 Y-AXIS

Z-AXIS

150.0 V

150.0 V

EXT

INT

EXT

EXT

INT

INT

ENABLE PO WER MASTER SCAN

L. De Sio et al. Appl. Opt. 45, 3721-3727 (2006)

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Experimentals Results Without thermo-acoustic isolation

100

Feedback ON

80

80

60

60

Position (nm)

Position (nm)

100

40 20 0 -20 -40 -60

Feedback OFF

Feedback ON

40 20 0 -20 -40 -60

Feedback OFF

-80

-80

-100

-100 0

200

400

600

800

1000

Time (sec)

500

1000

1500

2000

Time (sec)

L. De Sio et al. Appl. Opt. 47, 1363-1367 (2008)

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0

2500

3000

POLICRYPS: the recipe

Photo-polymerization process Nematic molecule

homogeneous mixture

Monomer molecule Polymer molecule

Diffusion process

n

n

POLICRYPS grating

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POLICRYPS Gratings Kogelnik theory    ng  L  2   sin [ ( L,  , ng ( E, T ), l )]  n0  l  cos  

  sin 2 

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L. De Sio and N. Tabiryan J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 3, 158-162.

Electro-optical comparison Transmittivity (arb. units)

1.0

LC droplets

0.8

dif tr dif + tr

0.6 0.4

Irregular polymeric walls

0.2 0.0 0.5

1.0

1.5

2.0

Applied Voltage (VRMS/ m)

Homogeneous LC Film in nematic phase

Transmittivity (arb. units)

0.0

1.0 0.8

dif tr dif + tr

0.6 0.4 0.2

Sharp morphology 0.0 0

1

2

3

4

Applied Voltage (VRMS/ m)

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5

Looking through a POLICRYPS

Ambient light

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Radial liquid crystals alignment on curved polymeric surfaces

Recording setup

Electro-optical response

L. De Sio, N. Tabiryan, T. Bunning Applied Physics Letters 2014, 104 (22), 221112. [email protected]

Different Materials • Cholesteric LC

Best Result

• Ferroelectric LC A

• Azo LC

•……….. •…………

P

? 30m Single-Step POLICRYPS (azo-LC)

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Polymeric Selective Etching Processtemplate A

P

? A

P

After 1 Hour

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A

P

After 2 Hours

A

P

After 3 Hours

Universal template

POM

SEM

• LIQUID CRYSTALS • METAMATERIALS • PHOTONIC SENSORS • MAGNETIC DIFFRACTION • DYE LASERS • OPTICAL MICROCHANNELS

• WAVEGUIDE ARRAYS • …….. L. De Sio , S. Ferjani, G. Strangi, C. Umeton, R. Bartolino “Universal Soft Matter Template For Photonic Applications” Soft Matter 7, 3739-3743 (2011) paper selected in the top five hot-articles

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Template Assisted Method 1. The periodic structure is filled by capillary force in isotropic phase 2. After the filling process the system is cooled down at room temperature by using a rate of 0.5 deg/min

Tup

LC PHASES

1) Nematics for grating purposes 2) Cholesterics for optical activity features 3) Chiral smectics for ferroelectric fast switching 4) 2-D composite matrices for photonics

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Tdown

All-Optical diffraction gratings Visible spectrum of CPND-57 azo-LC (red curve) and Methyl-Red (blue curve)

Photoisomerization process

hν hν’ KT Templates filled with MR (a) and azo-LC (b) Probe- Pump setup

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L. De Sio, et al. Adv. Mater., 22, 2316-2319, 2010

Control of diffracted light by using light trans-cis c

cis-trans c

Comparison between the reversible and repeatable changes of the diffraction efficiency of the MR based sample (a) and azo-LC based sample (b) [email protected]

L. De Sio et al.J. Mater. Chem. 21, 6811 (2011) L. De Sio et al.J. Mater. Chem. 22, 6669 (2012)

Uniform Lying Helix (ULH) Alignment SHORT PITCH CLC (BLO94)

ULH TEXTURE

P

A Helical Flexoelectro-Optic Effect

CONIC TEXTURES

G. Carbone et al. , APL, 95, 011102 (2009) [email protected]

L. De Sio et al. J. Phys. Chem. B, 2013, 117 , 1176

POLYMER WALLS INDUCED SSFLC Clark and Lagerwall, 1980

SSFLC (surface-stabilized ferroelectric liquid crystals), CS1024

= 3m L= 10 m P

P A

A Memory Capability

SSFLC Geometry inside the template

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L. De Sio et al. J. Phys. Chem. B, 2013, 117 , 1176

2D PERIODIC STRUCTURES

Far field diffraction pattern

L. De Sio et al. Optics Letters 35, 2759 (2010) [email protected]

Human Genomic DNA By capillary flow, we have injected a genomic DNA solution into the micro-channels of the polymeric template

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L. De Sio et al. Langmuir 2013 29 (10) 3398.

Human Genomic DNA

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L. De Sio et al. Langmuir 2013 29 (10) 3398.

Plasmonic nanomaterials Metallic (Au, Ag, etc) nanoparticles (NPs) are used as building blocks for realizing new generation of nanomaterials

Localized Surface Polariton Resonance Color variations arising from changes in the composition, size, and shape of nanoparticles

Mie Theory: Extinction coefficient



 ext    9  m V0 c

3/2

 2   1    2 m    2   2

2 L.M. Liz-Marzan, Mater. Today 2004, 7, 26-31.

Dielectric function of the medium surrounding the metallic nanoparticles

Liquid Crystal as active dielectric medium

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Universal Soft Matter Template Mixture

Harima Gold nanopaste NPG-J (20 %) BL098 CLC by Merck (helix pitch  400 nm)

A

Room temperature High temperature ( 90 ° C)

P

SEM view 1 cm

CLC

CLC + NPG- J

1.

The empty periodic structure is filled by capillary force in isotropic phase (90 °C )

2.

After the filling process the system is cooled down at room temperature by using a rate of 0.5 deg/min

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POM view

TOWARDS METAMATERIALS Top-Down Helps / Meets Bottom-Up

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Spectral response of the sample to external electric field

Δn (grating index contrast) P-polarization: Δn= n┴ - np 1.64-1.54= 0.1 S-polarization: Δn= n// - np 1.56-1.54= 0.02

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n// n┴

Spectral response of the sample to temperature variation

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L. De Sio et al. J. Mater. Chem. 21, 18967 (2011) paper selected in the top five hot articles

Conclusion



POLICRYPS: OPTICAL AND ELECTRO - OPTICAL PROPERTIES

 POLICRYPS: UNIVERSAL POLYMERIC TEMPLATE

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Coworkers

BEAM Co.

AFRL  Dr. Timothy Bunning

 Dr. Nelson Tabiryan

UNICAL  Prof. Roberto Bartolino  Prof. Cesare Umeton  Dr. Roberto Caputo

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WE SOLVE EXTRAORDINARY PROBLEMS IN OPTICS

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