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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.
Midwest Chapter- The society for Information Display
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
Holographic Polymerization
-10 0 10 20 30 40 50 60
0
2
4
6
8
10
Y A
xis
Title
X Axis Title
B
Multiple light beam interference + photosensitive materials
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
Liquid Crystals Phases
The fourth state of matter
• Long range order
• Broad band range of birifringence
• High sensitivity to AC, DC and Optical field
Liquid Crystals
Holographic Polymer Dispersed Liquid Crystals (H-PDLC)
Holographic photopolymerization
Drawbacks• Scattering
• High switching voltage
Pavani, K. et al. (2009). Journal of Optics A: Pure and Applied Optics
Bunning et al. (2000), Annual Review of Material Science 30, 83
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
University of Calabria
Stable setupUnstable setup
-10 0 10 20 30 40 50 60
0
2
4
6
8
10
Y A
xis
Title
X Axis Title
B
Stability problems during curing
Unstable setup
-10 0 10 20 30 40 50 60
0
2
4
6
8
10
Y A
xis
Title
X Axis Title
B
Stability problems during curing
Irregular morphology
High switching voltages
Possible solutions
+Ar Laser
2qcur
BEl/2
P
BS
M
M
PD 1
PD 3
PD 2
S
P
S
Piezo-Mirror
150.0 V 150.0 V 150.0 V
THORLABS 3-AXIS PIEZO CO NTRO LLER MO DEL MDT693
EXT EXT EXTINT INT INT
EXT INT
ENABLE
PO WER
X-AXIS Y-AXIS Z-AXIS
MASTER SCAN
PID system
VPD
VPS
BS
2qcu
r
BEl/2
PD2
PD1
PD3
Ar+ Laser
M
Passive setup Active setup
High response time
Passive setup
without stabilization
with stabilization
0 100 200 300 400 500 600 700 800 900 1000-60
-50
-40
-30
-20
-10
0
10
20
30
exp(d
eg
)
time (sec.)
0 200 400 600 800 1000-30
-20
-10
0
10
20
30
e
xp(d
eg
)
time(sec)
Active setup
P
S
Piezo-Mirror
150.0 V 150.0 V 150.0 V
THORLABS 3-AXIS PIEZO CO NTRO LLER MO DEL MDT693
EXT EXT EXTINT INT INT
EXT INT
ENABLE
PO WER
X-AXIS Y-AXIS Z-AXIS
MASTER SCAN
PID system
VPD
VPS
BS
2qcur
BEl/2
PD2
PD1
PD3
Ar+ Laser
M
L. De Sio et al. Appl. Opt. 45, 3721-3727 (2006)
0 200 400 600 800 1000-100
-80
-60
-40
-20
0
20
40
60
80
100
Feedback OFF
Po
sit
ion
(n
m)
Time (sec)
Feedback ON
0 500 1000 1500 2000 2500 3000-100
-80
-60
-40
-20
0
20
40
60
80
100
Feedback OFFFeedback ON
Po
sit
ion
(n
m)
Time (sec)
Experimentals Results
Without thermo-acoustic isolation
L. De Sio et al. Appl. Opt. 47, 1363-1367 (2008)
POLICRYPS: the recipe
Monomer molecule
Nematic molecule
Polymer molecule
homogeneous mixture
Photo-polymerization process
Diffusion process
POLICRYPS grating
n n
2 2
0
sin sin [ ( , , ( , ), )]cos
g
g
n LL n E T
n
l
l
Kogelnik theory
POLICRYPS Gratings
L. De Sio and N. Tabiryan J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 3, 158-162.
0.0 0.5 1.0 1.5 2.00.0
0.2
0.4
0.6
0.8
1.0
dif
tr
dif + tr
Applied Voltage (VRMS
/ m)
Tra
nsm
ittivity
(arb
. units)
0 1 2 3 4 50.0
0.2
0.4
0.6
0.8
1.0
dif
tr
dif + tr
Tra
nsm
ittivity
(arb
. units)
Applied Voltage (VRMS
/ m)
LC droplets
Irregular polymeric walls
Homogeneous LC Film in
nematic phase
Sharp morphology
Electro-optical comparison
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.
Different Materials
• Cholesteric LC
• Ferroelectric LC
• Azo LC
•………..
•………… ?
Best Result
Single-Step POLICRYPS
(azo-LC)
30m
P
A
Polymeric template
After 1 Hour After 2 Hours
?
After 3 Hours
PA
PA
PA P
A
Selective Etching Process
POM SEM
Universal template
• 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
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
Template Assisted Method
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
LC PHASES
Tup Tdown
hν
hν’ KT
Photoisomerization process
All-Optical diffraction gratings
Probe- Pump setupTemplates filled with MR (a) and azo-LC (b)
Visible spectrum of CPND-57 azo-LC (red curve) and Methyl-Red (blue curve)
L. De Sio, et al. Adv. Mater., 22, 2316-2319, 2010
Control of diffracted light by using light
c c
trans-cis cis-trans
Comparison between the reversible and repeatable changes of the diffraction efficiency
of the MR based sample (a) and azo-LC based sample (b)
L. De Sio et al.J. Mater. Chem. 21, 6811 (2011)L. De Sio et al.J. Mater. Chem. 22, 6669 (2012)
SHORT PITCH CLC (BLO94)
Helical Flexoelectro-Optic Effect
Uniform Lying Helix (ULH) Alignment
P
A
ULH TEXTURE
CONIC TEXTURES
G. Carbone et al. , APL, 95, 011102 (2009)
L. De Sio et al. J. Phys. Chem. B, 2013, 117 , 1176
SSFLC Geometry inside the template
POLYMER WALLS INDUCED SSFLC
PA
P
A
= 3m
L= 10 m
Memory Capability
SSFLC (surface-stabilized ferroelectric liquid crystals), CS1024Clark and Lagerwall, 1980
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)
Human Genomic DNA
By capillary flow, we have injected a genomic DNA solution into the micro-channels of the polymeric template
L. De Sio et al. Langmuir 2013 29 (10) 3398.
Plasmonic nanomaterials
Localized Surface Polariton Resonance
L.M. Liz-Marzan, Mater. Today 2004, 7, 26-31.
Color variations arising from changes in the
composition, size, and shape of nanoparticles
23/2
0 2 2
1 2
92
ext m
m
Vc
Mie Theory:
Extinction coefficient
Dielectric function of the medium surrounding the metallic nanoparticles
Liquid Crystal as active dielectric medium
Metallic (Au, Ag, etc) nanoparticles (NPs) are used as building blocks for
realizing new generation of nanomaterials
Universal Soft Matter Template
1 cm
A P
POM view
SEM view
Harima Gold nanopaste NPG-J (20 %)
BL098 CLC by Merck (helix pitch 400 nm)
Mixture
CLC CLC + NPG- J
Room temperature High temperature ( 90 ° C)
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
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
n//n┴
Spectral response of the sample to temperature variation
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
Coworkers
Prof. Roberto Bartolino
Prof. Cesare Umeton
Dr. Roberto Caputo
UNICAL
BEAM Co.
Dr. Nelson Tabiryan
AFRL
Dr. Timothy Bunning
