LABORATOIRE DE PHYSIQUE DES LASERS Photonique Organique et Nanostructures Photonique Organique et Nanostructures Support de thèse : ANR OLD-TEA Direction de thèse : Alexis Fischer et Azzedine Boudrioua Encadrement : Mahmoud Chakaroun Assistance technologique Jeanne Solard Collaboration: Chii-Chang Chen ,National Central University , Taiwan Investigation of photonic properties of self Investigation of photonic properties of self organized nanoparticles monolayers : organized nanoparticles monolayers : application to photonic crystal cavities and application to photonic crystal cavities and patterned organic light emitting diodes patterned organic light emitting diodes Getachew T. AYENEW PhD defence : July 8th, 2014
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LABORATOIRE DE PHYSIQUE DES LASERS Photonique Organique et Nanostructures Support de thèse : ANR OLD-TEA Direction de thèse : Alexis Fischer et Azzedine.
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LABORATOIRE DE PHYSIQUE DES LASERS
Photonique Organique et Photonique Organique et NanostructuresNanostructures
Support de thèse : ANR OLD-TEADirection de thèse : Alexis Fischer et Azzedine Boudrioua Encadrement : Mahmoud ChakarounAssistance technologique Jeanne Solard
Collaboration: Chii-Chang Chen ,National Central University , Taiwan
Investigation of photonic properties of Investigation of photonic properties of self organized nanoparticles self organized nanoparticles
monolayers : application to photonic monolayers : application to photonic crystal cavities and patterned organic crystal cavities and patterned organic
light emitting diodeslight emitting diodesGetachew T. AYENEW
PhD defence : July 8th, 2014
Thank you mister president.My name is Ayenew Getachew, and I'm going to present you my work entitled Photonic properties....This work was done under the supervision of....Prof Fischer and Boudrioua as thesis director in collaboration with Prof. Chii-chang Chen from NCU Taïwan
Outline
1. Introduction► Context
► State of the art
► Our approach
2. Photonic properties of monolayer of opals and inverse-opals► Numerical study of photonic band gaps
► Numerical study of microcavities
► Experimental approach of characterizing monolayer of opals
3. Nanoparticle based 2D patterning of OLED► 2D pattering of surfaces
► 2D patterning of OLEDs
4. Conclusion and perspectives
2
My talk is divided in two main section :I will first introduce my work and its context. In the second part I will present investigations on the photonic properties of nanostructures based onself organized nanoparticules.In the third chapter I will presetnn experimental results on nanoparticle based 2dimensional patterning of OLEDI will finish with a conclusion and perspectives.
3
1D Vertical confinement
Top down Bottom up
Small Mode
volume
High Q
Extended cavity
1. Introduction
Context :ANR OLD-TEA 2010-2013
Axe 1
Organic Laser Diode : A Threshold-Less Experimental Approach
Axe 2
2D lateral confinement
Photonic Crystal Opals - Inverse Opals
Low threshold organic diode laser
2D DFB lasers
Light extraction in OLED
Potential Applications
The context of this work deals with the quest of the organic laser diode which has not been demonstrated so far. The Organic Photonic and Nanostructures group adress this quest with a low-threshold laser approach. The group is involved in embedding OLED in different type of microcavities. This requires high Q and or low mode volume laser cavities so as to lower the laser threshold at the level of the highest current density in OLED.Axe 1 deals with Fabry-perot type of microcavities, whereas axe 2 consider photonic crystal nanocavities. In a previous thesis done by Franocis Gorudon very low laser threshold were obtained with defect cavity in photonic crystal realize by a top-down approach with an e-beam and ICP etching.The goal of my thesis is to investigate if opals and inverse opals can be used in a bottom up approach to design and fabricate photonic crystal
► Photonic properties of monolayer of nanoparticles and microcavities
► New patterning technique using nanoparticles 4
1. Introduction
Objectives of the study
Self-organized Nanoparticles
Photonic crystals OLED Nanostructuration
Photonic crystal laserwith defect microcavity
2D-DFB OLD Light extraction in OLED
► Photonic properties of monolayer of nanoparticles and microcavities
► Making nanostructures using nanoparticles 5
1. Introduction
Objectives of the study
Self-organized Nanoparticles
Photonic crystals OLED Nanostructuration
Photonic crystal laserwith defect microcavity
2D-DFB OLD Light extraction in OLED
6
State of the artPolymeric solid-state dye lasers resonator
Shi et al. Appl. Phys. Lett. 98, 093304 (2011)
Random lasingDye doped photonic crystal
Kim et al Chem. Mater., 2009, 21 (20), pp 4993–4999 Murai et al, Chemistry LettersVol. 39 (2010) , No. 6 p.532
porous photonic film enhanced stimulated emission Lasing by randomly dispersing nanoparticles into a gain material• multiple scattering
highly-efficient low threshold laser
Emission spectra of the resonator cavity below and above lasing threshold
2. Photonic properties of monolayer of opals and inverse-opals
►General objective► Optimal design of planar photonic
crystal using nanoparticles ?► Microcavity ?
►Methodology
► Investigate numerically photonic band gaps in monolayer of dielectric spheres
► Investigate numerically quality factors of microcavities
► Experimental investigation of in-Plane propagation 7
glass
General objective/Methodology
0.2 0.3 0.4 0.5
0.0
0.2
0.4
0.6
0.8
1.0
Transmission spectrum
Cavity response
Normalized Frequency(a/)
Tra
ns
mis
sio
n
0
20
40
60
80
100
Inte
ns
ity
(a.u
.)
2. Photonic properties of monolayer of opals and inverse-opals
Opal without substrate
8
Structures
glass
air
air
air
2r
air
air r
air
glass
a
Inverse opal without substrate
Opal with substrate Inverse opal with substrate
r
a
a = period r = radius
2. Numerical study of photonic band gaps
Control parameters
2. Numerical study of photonic band gaps
ra
9
2__
33
4
___
__
a
r
cellun ito fV o lum
sphereso fV o lum eff ce llun itinspheres
Refractive index (n)• n of spheres in opals• n of infiltrated material in inverse-
opals
Compactness of spheres , r/a ratio ( for n = 2.5, anatase TiO2)
• r/a=0.5, compact spheres• r/a < 0.5 non- compact spheres• r/a ratio determines the filling factor
Substrate effect : effect of compactness on losses
2. Numerical study of photonic band gaps
compacthigh neff
non-compactlow neff
Less compactMore losses
compactlow neff
non-compact high neff
Morecompact
More losseslarger filling factor
smaller filling factor
Opals Inverse-opals
air
opal, r/a = 0.5
glass
zy
x
glass
air
opal, r/a = 0.31
glass
air
inverse opal, r/a = 0.31
glass
air
opal, r/a = 0.31
20
Substrate effect : effect of compactness on losses
2. Numerical study of photonic band gaps
Compact opalshigh neff
Non compactlow neff
More losses
compactlow neff
Non compactInverse-opal
high neff
More losses
►General objective► Optimal design of planar photonic
crystal using nanoparticles ?► Microcavity ?
►Methodology
► Investigate numerically photonic band gaps in monolayer of dielectric spheres
► Investigate numerically quality factors of microcavities
► Experimental investigation of in-Plane propagation 21
glass
General objective/Methodology
0.2 0.3 0.4 0.5
0.0
0.2
0.4
0.6
0.8
1.0
Transmission spectrum
Cavity response
Normalized Frequency(a/)
Tra
ns
mis
sio
n
0
20
40
60
80
100
Inte
ns
ity
(a.u
.)
2. Photonic properties of monolayer of opals and inverse-opals
► Investigation with respect to► Various cavity geometries► The r/a ratio► with and without substrate (effect of the losses)
H1 L5L3H2
Microcavities
► Fixed refractive index n= 2.5► Defects in the periodicity
monitor source
2. Numerical study of microcavities
22
► Without substrate:► Cavity resonance in the
PBG
► With substrate► Significant resonant peaks
observed for non-compact arrangement
Microcavities in inverse-opals
2. Numerical study of microcavities
23
► Quality factor increases when r/a < 0.40► The presence of glass substrate reduces the quality factor► The maximum of the Q-factor is obtained for 0.3 < r/a < 0.35
24
Microcavities in inverse-opals with and without
2. Numerical study of microcavities
0.1 0.2 0.3 0.4-5.00E+012
0.00E+000
5.00E+012
1.00E+013
1.50E+013
2.00E+013
2.50E+013
3.00E+013
3.50E+013
Inte
ns
ity
(a
.u.)
n=3,2 air resonance r/a=0,5 n=3,2 glass resonance r/a=0,5n=4, glass r/a=0,5
Normalized wavelength ( a/)
Inte
ns
ity
(a
.u.)
0.00E+000
2.00E+009
4.00E+009
6.00E+009
8.00E+009
1.00E+010
25
H2
Higher refractive index values needed in opals to achieve a resonance: (n~4 realistic?)
► The inverse-opal arrangement is more favorable to microcavities
Microcavities in opals
2. Numerical study of microcavities
n=4
n=3.2
n=3.2
►General objective► Optimal design of planar photonic
crystal using nanoparticles ?► Microcavity ?
►Methodology
► Investigate numerically photonic band gaps in monolayer of dielectric spheres
► Investigate numerically quality factors of microcavities
► Experimental investigation of in-Plane propagation 26
glass
General objective/Methodology
0.2 0.3 0.4 0.5
0.0
0.2
0.4
0.6
0.8
1.0
Transmission spectrum
Cavity response
Normalized Frequency(a/)
Tra
ns
mis
sio
n
0
20
40
60
80
100
Inte
ns
ity
(a.u
.)
2. Photonic properties of monolayer of opals and inverse-opals
► Objectives► Measure of the In-Plane
transmission spectra as a function of
► Polarization (TE, TM)
► Crystal direction (M, K)
► Problem ► Arrangement of spheres –
presence of multiple domains► Several directions are probed at
the same time
► Method► Fabrication of a single domain
monolayers ?► Characterization of single
domain ?27
2. Towards experimental study of in-plane propagation in opal monolayers
Problem and method
transmittedtransmitted
Direction of propagation
Light ΓM
ΓK
Reference
waveguide
nanoparticlesmicro-
hexagon
► Single domain fabrication► Fabrication of micro-hexagons
► force nanoparticles organizaton in ordered manner
► Orientation of hexagons to fixe the direction of propagation
► Dimension calculated for given nanoparticle diameter
► Single domain characterization► Waveguides
• Polymer waveguide on a glass substrate
• In- and out-coupling• Single domain probing
2. Towards experimental study of in-plane propagation in opal monolayers Approach: single domain samples and characterization
28
29
10µm
2. Towards experimental study of in-plane propagation of opal monolayers
► Clearly defined waveguide structure and micro-hexagon
► Different orientations of the micro-hexagons
► The diameter of the microneedle is too large as compared to the size of the micro-hexagon► Nanoparticles not in the target area
30
► 1.5µm spheres used for optimization of the process
2. Towards experimental study of in-plane propagation of opal monolayers
Preliminary experimental results: Deposition of nanoparticles
31
2. Towards experimental study of in-plane propagation of opal monolayers
Conclusion and perspectives on experiments part 1
► Conclusion► Method of micro-hexagon
promising to make single-domain monolayers
► Waveguides can enable in- and out- coupling from the nanoparticles
► Deposition by micro-needles not successful
► Perspective► Deposition by microfluidic channels
– easy to deliver the nanoparticle solution to micro-hexagon
Adv. Funct. Mater., Vol.19, 1247–1253(2009)
32
Conclusion and perspectives part 1
► Numerical investigation on opals and Inverse opals► Photonics bandgap exist in Opals and Inverse-Opals ► The inverse-opal structure exhibits larger PBG than the
opal structure► Non-compact inverse-opal structure has highest Q-factor ► Opal micro-cavities require high refractive index to have
cavity resonances► Experimental study of propagation in opals
► In-plane propagation experiment of single domain opals►Micro-hexagons►Waveguide
The array of self-organized micro nanoparticles is both a collection of ball-lenses and a 2D-phase mask
1
44
Red OLED
Green OLED
3. 2D nanostructuration of OLED
glassITO
patterned photoresist
Micro-OLEDS: Organic hetero-structures - band diagram
45
3. 2D nanostructuration of OLED
Micro-OLEDs: Images
► Micro-OLED sizes = 1.27µm
► Method compatible with OLED operation
46
3. 2D nanostructuration of OLED
Micro-OLEDs: Spectra
► Emission under normal incidence► Small spectral modification of
emitted light as compared to large area OLED
► Perspectives► Measurements for other angles of
emission► Edge emission► Smaller period of pattern
glass
► Conclusion► Cheap, simple method to pattern 2D surfaces on large area► The patterning method is compatible with OLED deposition
47
Conclusion and perspective part 2
► Perspective► Characterization of the emission
• Measurement of the emission diagram• Edge emission
► Towards 2D-DFB laser :• Smaller lattices : 200-300 nm• Lower exposure wavelength (<405nm) to increase the
resolution of the nanoparticles lithography process• Deep UV (DUV) lithography and DUV photoresist
► Use negative photoresist to make periodic pattern of micro nano-pillars
3. 2D nanostructuration of OLED
48
Photonic properties of opal and inverse-opal monolayers► Monolayers of O and I-O do exhibit photonic bandgap► The inverse-opal structure exhibits larger PBG► Non-compact (r/a=0.4) TiO2 inverse-opals exhibit the largest PBG► Highest Q-factor is obtained in inverse –opals for r/a ratio ~ 0.32.► Opal micro-cavities require high refractive index to exhibits cavity
resonances
► Nanoparticle photolithography► Monolayers of nanoparticles used to make periodic pattern on
photoresist• Lattice down to 750 nm• Holes down to 450 nm
• 2D-DFB organic laser fabrication requires Deep-UV photolithography (193 nm)• Applications of the nanoparticle photolithography technique : Patterning
surface with metal (SERS, Molecules detection, OLED efficiency increases via Surface Enhanced Plasmon Resonance.
4. General Conclusion
Thank you for your attention
49
► Conclusion ► Structures without substrate exhibit PBGs for wide range of
refractive indices and compactness► Generally inverse opals have larger photonic bandgap
width► Structures with substrate have losses for lower refractive index
materials► Considering n=2.5, lower compactness in inverse opals
and higher compactness in opals result in lower losses to glass substrate
► Inverse-opal with lower compactness on glass substrate seems to be a good compromise between the losses and the width of PBG
► Thus microcavities designed in non-compact sphere inverse-opals are expected to have better confinement► Calculation of quality factors is necessary to optimize the
optimum r/a value for a given refractive index50
Conclusion
2. Numerical study of photonic band gaps
► Highest Q-factor(~300) obtained for non-compact spheres in inverse-opals.
► With a glass substrate the Q factor is limited to Q~200
► Glass substrate reduces Q-factors
► Micro-cavities in opals require refractive index larger than n=3.2 which is hardly feasible
► The literature presents much higher Q-factor in conventional Phc Slabs.
51
Conclusion on Microcavities
2. Numerical study of microcavities
52
sample
2. Towards experimental study of in-plane propagation of opal monolayers
Preliminary experimental results: Deposition of nanoparticles
emitting diode based on self-organized nanoparticles photolithography” Submitted to optics Express (may 2014)
► F. Gourdon, A.P.A. Fischer, M. Chakaroun, G. Ayenew and Azzedine Boudrioua “Study of the organic layer thickness effect in a hybrid photonic crystal L3 nanocavity under optical
pumping”, Accepted in Journal of Nanophotonics, 5 may 2014
► Min Won Lee, Siegfried Chicot, Chii-Chang Chen, Mahmoud Chakaroun, Getachew Ayenew, Alexis Fischer, and Azzedine Boudrioua, Study of the Light Coupling Efficiency of OLEDs Using
a Nanostructured Glass Substrate , Journal of Nanoscience, Volume 2014 (2014)
of two-dimensional photonic crystals based on monolayer of dielectric nanospheres » Poster SPIE 16 - 19 April 2012, Square Brussels Meeting Centre Brussels, Belgium.
► Getachew T. Ayenew, Anthony Coens, Mahmoud Chakaroun, Jean Solard, Alexis P. A. Fischer, Chii-Chang Chen, Chia-Hua Chan, Azzedine Boudrioua, Micro-Oled
fabricated by microsphere based lithography, Optique Paris 13, 8 au 11 juillet 2013, Villetaneuse, Présentation Orale.
► Getachew T. Ayenew, Anthony Coens, Mahmoud Chakaroun, Jeanne Solard, Alexis P. A. Fischer, Chii-Chang Chen, Chia-Hua Chan, Azzedine Boudrioua, Micro-OLED
fabricated by microsphere based photolithography, JNRDM 2013, Journées National du Réseau Doctoral en Micro-Nanotechnologies, 10-12 juin 2013, Minatec Phelma,
Grenoble, Poster
30 à 50%
Analyse du problème de l'émission lumineuse
La structure OLED• Interfaces
– ITO / Verre
– Verre /air
Impact sur l'extraction lumineuse• Réflexions aux interfaces :
– 0,8%<R ITO/Verre <19%
– R Verre/air 4%
• Angles limites : lim = Arcsin(n2/n1)
• Réflexion totale interne (TIR)
• Modes guidés dans le verre : 30%
• Modes guidées dans l'ITO : 50%
Taux de couplage : 15 à 20 %
Aluminium
Organiquen=1,7
n=1,8 à 2,2
n=1,5
Verre
2
1
lim
TIR
50 à 30%
Modes guidés
Modes guidés
TIRITO
2
lim
Lumière extraite15% à 20%
R=(n1−n2
n1+n2)2
Impact des angles limites
A partir de la loi de Descartes• n2sin() = n1sin()
• Angles limites : lim = Arcsin(n2/n1)
• ITO/verre : 43°lim<56°
• Verre/Air : lim 42°
• ITO/air : 27°lim<33° (limpour n=2)
• Au delà de l'angle limite il y a réflexion totale interne (TIR) (onde guidée)
Taux de couplage• Ce qui est transmis : T() r2 sind• T() transmittance en fonction de l'angle
• Couplage externe ITO/Air : 15 %
Transmission au delà des angles limites?• Modification de la géométrie grâce aux