Title: Organic Photonic Polymer Thin Films: Fundamental and Applications
1Organic Photonic Polymer Thin Films Fundamental
and Applications
2Outline
- Opto-electronic properties and applications of
conjugated organic molecules and polymers - Optical poling of azo-dye and DANS polymer thin
films - Optically induced anisotropy of third order
susceptibility in azo-dye and DANS polymer thin
films - Polymer photonic crystals
- Conclusions
3- Opto-electronic properties of conjugated organic
molecules and polymers
- Conjugated an alternation of double and single
bonds linking a sequence of atoms.
Conjugated molecule
Conjugated polymer
-electrons in conjugated molecules (or
polymers) are delocalized, which makes the
-electron distribution highly deformable in
conjugated molecules (or polymers). That is why
conjugated molecules (or polymers) has large
optical nonlinearities.
4- Nonlinear optical response of noncentrosymmetric
conjugated molecules
5- Bond alternation and band gap
6Trans-cis photoisomerization effect
7Comparisons between organic and inorganic
materials
8Potential applications
- OLED, PLED
- Laser frequency conversion
- Holography memory
- Electro-optic modulation
- All optical modulation
- Optical data storage
- Polymer photonic crystal devices
9Polymer Light Emitting Diodes (PLED)
Microdisplay with CDT Green Polymers
10Toshiba PLED Full Color Display
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13POLYMER LIGHT EMITTING DIODES
14 15POLYMER LIGHT EMITTING DIODES
16POLYMER LIGHT EMITTING DIODES
17Electric field poling
Use Electric field poling technique to generate
non-centro symmetric distribution of conjugated
dye molecules.
18Optical poling of dye polymer materials
19DR1/PMMA absorption spectrum and molecules
structure
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22Polar excitation of molecules
Excitation probability of a 1D molecule by a
linearly polarized light
Under optimized poling conditions
Polar axis(polarization of seeding beams)
Molecular dipole moment
Probability of excitation as function of the
polar angle ? under optimized poling conditions
23Angular hole burning
24The evolution of the molecular angular
distribution (a) before poling (b) after few
minutes of seeding the sample with optical poling
field E?E2? (c) the final distribution after
several hours of the poling .
Molecular angular redistribution
25Real time optical poling experimental setup
26Traditional probe configurations
27Basic concept of our new method
28Polarization properties of ?(2)
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30Real-time monitoring of ?(2) buildup
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32Photoinduced nonlinear optical phenomena in
DANS-PMMA polymer thin films
In azo-systems, the optical anisotropy caused by
the AHB disappear in few second after the pump
beam is switched off, because of the thermal
relaxation from cis to trans. Stilbene
derivatives (e.g. (DANS)) also experience
trans-cis photoisomerization, but no visible
cis-trans thermal relaxation has been detected.
The irreversible trans-cis in DANS polymers
photoisomerization is attractive for permanent
optical memories.
33Simplified four-level scheme of trans-cis
photoisomerization in DANS
Dynamics of trans population is described by
equation
34Optical poling of DANS-PMMA thin films
Growth of the square root of SH signal in
DR1-PMMA (a) and DANS-PMMA (b) samples (in
arbitrary unites). The experimental data are
fitted to functions f(t)A1(1-exp(-t/?A1))A2(1-ex
p(-t/?A2)) for the DR1-PMMA sample and
f(t)-B((1-B1)exp(-t/?B1)B1)B((1-B2)exp(-t/?B2)
B2) for the DANS-PMMA sample. The following fit
parameters are used A15.4, A22.1 ?A11.7
min,?A219.3 min B9.3, B10.80, B20.91,
?B10.46 min, ?B28.3 min.
35Conclusions
- Simultaneous writing and probing photoinduced
second order susceptibility ?(2) in azo-dye
polymer thin film is demonstrated. This technique
allows to monitor the ?(2) value in real time
excluding completely unwanted meddling into the
optical poling process and to retain the simple
and effective poling setup with co-propagating
fundamental and seeding beams. - The real time optical poling technique is based
on properties of ?(2) response providing
different planes of polarization for seeding and
signal second harmonics. - The optical encoding of macroscopic ?(2) in
DANS-PMMA thin films has been demonstrated and
physical interpretation based on the AHB model is
given. - The dynamics of photoinduced second order
nonlinearity in the DANS-PMMA thin film is
well-explained by the influence of reverse
cis-trans photoisomerization of HCCH bond.
365. The photoinduced second order nonlinearity in
DANS-PMMA has exhibited the better dark stability
than that in azo-polymers because of the absence
of thermal cis-trans relaxation.
- V. M. Churikov, M. F. Hung, and C. C. Hsu, 2000.
Real time monitoring all optical poling of
azo-dye polymer thin film. Optics Lett. 25, 960.
- V. M. Churikov, M. F. Hung, C. C. Hsu, C. W.
Shiau, and T. Y. Luh, 2000. Encoding of
macroscopic second order nonlinearity via
all-optical polar alignment in substituted
norbornene polymer thin films Chem. Phys. Lett.
332, 19.
- V. M. Churikov, and C. C. Hsu, 2001 Dynamics
of photoinduced second order nonlinearity in
dimethylamino-nitrostilbene polymer thin films,
Optics Comm, 190, 367.
37Optically induced anisotropy of third order
susceptibility in polymers
UV filter
?
3?
PMT
?
DR1-PMMA
2?
38Primary experiment
UV filter
3?
PMT
3?
DR1-PMMA
2?
39Experimental setup
40Angular hole burning without rotation
Original isotropic distribution
Molecular reorientation
The arrows represent dipole moments of trans
molecules. Excitation probability is proportional
to cos2 ?
Some trans molecules with angles ? close to 0 or
180o (gray arrows) are missed (transformed to
cis) and no longer contribute to ?(3)
The number of trans molecules remains the same,
but some molecules are reoriented to the
position with lower excitation probability
41Model of photoinduced anisotropy of ?(3)
susceptibility in azo-polymers
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45DR1-PMMA (guest-host system)
46DR1-PMMA (side-chain system)
47Experimental results
48TH intensity as a function of time in the sample
pumped by a cw He-Cd laser. The sample was probed
by the fundamental co-polarized () and
perpendicularly polarized (?) with the pumping
beam.
49TH intensity as a function of time in the sample
pumped by a SH of NdYAG laser. The sample was
probed by the fundamental co-polarized () and
perpendicularly polarized (?) with the pumping
beam. The curves for - and ?-cases are
normalized to the same initial level and
represent a relative change of the TH generation
level.
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51TH intensity as a function of polarization angle
? of the probing beam before pumping (first
column from the left), after 8 min of pumping
with the 532 nm and 442 nm light of 0.3 W/cm2
average intensity (a,b) and 442 nm light of 3
W/cm2 intensity (c) (second column), after 1 min
of dark relaxation (third column) and after
following 15 min of dark relaxation (fourth
column). The zero angle corresponds to the plane
of polarization of a pump.
52Homopolymer absorption spectrum and molecules
structure
53Homopolymer
54Homopolymer
55DR1-PMMA
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58Photoinduced THG decay and recovery in DANS-PMMA
thin films at room temperature
Pumped at 1064 nm
Pumped at 532 nm
59THG recovery in DANS-PMMA thin films at high
temperature
60Conclusions
- One- and two-photon induced molecular
conformation change and reorientation effects
produce large reversible anisotropic THG
variation in azo polymer thin filmss. - The observed THG anisotropy agrees qualitatively
with the prediction of theoretical model. - The effect can have potential applications in
multi-photon hole-burning holographic storage
devices. - Temperature dependent photoinduced change of THG
in polyurethane homopolymer and DR1-PMMA thin
films has been compared. - Photoinduced THG variations in both samples are
smaller at high temperature because of the
decrease of cis states lifetime and population
and large orientational diffusion constant.
61- 6. THG recovery experiment show that the
photoinduced THG change in the polyurethane
homopolymer sample is more stable than that in
the DR1-PMMA sample, consistent with its large
molecular weight and small free volume. - Photoinduced THG decay in DANS-PMMA thin films is
irreversible when the samples are pumped at 1064
nm or 532 nm in air environment. The permanent
THG decay is likely due to the phtoinduced
oxidation of DANS molecules in the films. - Photoinduced THG decay in DANS-PMMA thin films
can be fully recovered at room temperature when
the samples are pumped at 1064 nm in nitrogen
environment. - The THG signal is only partially recovered when
the samples are pumped at 532 nm in nitrogen
environment. However, the THG decay signal can be
fully recovered when the samples are heated up at
high temperature.
62- V. M. Churikov, and C. C. Hsu, 2000. Optical
control of third-harmonic generation in azo-doped
polymethacrylate thin films Appl. Phys. Lett.
77, 2095.
- V. M. Churikov, and C. C. Hsu, 2001. Optically
induced anisotropy of third- order susceptibility
in azo-dye polymers JOSA B 18, 1772.
- V. M. Churikov, J. T. Lin, H. H. Wu, J. H. Lin,
T. H. Huang, and C. C. Hsu, 2002 One- and
two-photon induced molecular conformation change
and reorientation and related third-order
nonlinearities in phenylamine azo-dye polymer
thin films, Optics Comm. 209, 451.
- C. C. Hsu, J. H. Lin, T. H. Huang, K. Harada,
2003. Temperature dependent photoiduced third
harmonic generation variation in azo homopolymer
and azo-doped polymer thin films Appl. Phys.
Lett.
63- V. M. Churikov, and C. C. Hsu, 2002.
Photoinduced third order nonlinear optical
phenomena in azo-dye polymer in Photoreactive
organic polymer thin films edited by Z. Sekkat
and W. Knoll, Academic Press, San Diego, P366-392.
64Polymer Photonic Crystals
- Photonic crystals (PC) are optical materials
with periodic variation of refractive index.
Analogous to a semiconductor crystal a periodic
refractive index distribution can produce a
photonic bandgap that blocks a range of optical
frequencies of light propagating inside a PC.
65Defect in photonic crystals
- If local disorders such as variations of
refractive index or geometry are introduced into
a PC, we may obtain localized defect modes whose
eigenfunctions are strongly localized around the
disorder.
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67Transmission spectra of 9 x 18 array of
cylinders. The incident wave comes along (a) the
1,0 , (b) the 2,1 , and (c) the 1,1
direction of the regular crystal without the
defect. In (d) , the orientation of the incident
wave is the same as in (a) , but a single
cylinder located at the center of the array is
removed. Note the sharp extra peak in the gap
located at 11.2 GHz signifyinga localized defect
mode.
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69http//www.tu-harburg.de/et7/forschung/crystal/cry
stal_e.html
70http//www.tu-harburg.de/et7/forschung/crystal/cry
stal_e.html
71http//www.tu-harburg.de/et7/forschung/crystal/cry
stal_e.html
72Self assembly polymer PC
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74CS2-PS(1-wt),100rpm,TE-CoolingRoom
Temp. ?????100C CS2-PS(1-wt)??
75CS2-PS(1-wt) 300rpm TE COOLINGRoom Temp.
Top View
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77??????
78Two-photon polymerization experimental setup
79????????27mW /cm2???????SEM?,?????????????1000?800
?500?200?100?80?50 ms,?????1µm
80??????L??????,???????????36mW /cm2,????15
ms,????700 nm
81???????????????????????,??????36mW /cm2,????20
ms,????234 nm
82????????,?????750nm,??2.4um,??????36mW
/cm2,?????10.4µm /s????????
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