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« Control of pattern formation in a single feedback system by photonic bandgap
structures »
Nicolas Marsal, Germano Montemezzani, Delphine Wolfersberger, Marc SciamannaLab. Matériaux Optiques, Photonique et Systèmes (CNRS - UMR 7132)
Université Paul Verlaine - Metzand SUPELEC France
Dragomir NeshevNonlinear Physics Centre, Research School of Physical Sciences and Engineering,
Australian National University, Canberra, Australia
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1. Introduction to pattern and photonic lattice
2. Our experimental setup
3. Results
4. Conclusions
Outline
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Pattern
Nonlinear medium
Free propagation
Single feedback
Linear cavity
Mirror
Photorefractive crystal, Kerr…
Liquid-crystal light valves (LCLV), Photorefractive crystal, Na vapors…
Lasers…
1. Patterns / photonic lattice
2. Setup
3. Results
4. Conclusions
Active medium
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Pattern : properties
• Light structures spatially modulated and correlated
• Generated thanks to noise and modulation instability
• Disordered or ordered geometry
Goal Control of pattern
1. Patterns / photonic lattice
2. Setup
3. Results
4. Conclusions
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Pattern : control
C. Denz, Ann. Phys. (Leipzig) 13, 391 (2004)
A.V. Mamaev, M. Saffman, Europhys. Lett. 34, 669 (1996)
C. Denz, Phys. Rev. Let. 81, 1614 (1998)
And with a photonic lattice … ?
R. Neubecker and A. Zimmermann, Phys. Rev. E 65, 035205 (2002)
E
Fourier Filter
External illumination
1. Patterns / photonic lattice
2. Setup
3. Results
4. Conclusions
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Photonic lattice
Light induced
photonic crystal
photonic crystal
Periodic illumination ( lattices or light
interferences )
Light sensitive medium ( photorefractive crystal )
Periodic variation of the refractive index inside the
medium
1. Patterns / photonic lattice
2. Setup
3. Results
4. Conclusions
Propertiesn1
n0
real space 1st and 2nd BZ
a
w = kc / n
Constant refractive index Periodic refractive index
Bandgap effect
2π / a
k space
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Experimental setup
1. Patterns / photonic lattice
2. Setup
3. Results
4. Conclusions
Goal Pattern control by a photonic lattice
MirrorPhotorefractive BaTiO3 crystal
Far field (k space)
External periodic illumination
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ff2
f2
f
BSP BS
Lattice
HWP
L1SF
LA
PC
2f 2f
LASER
FarField
M
L2
L3 L4
Horizontal polarization
Vertical polarization
4f system
M : Mirror
: Feedback loop
VM
BS : Beam SplitterHWP : Half Wave PlateBSP : Polarizing Beam Splitter L : Lens SF : Spatial Filter LA : Linear Atenuator PC : Photorefractive Crystal VM : Virtual Mirror
: Pattern beam: Lattice beam
λ = 532
Experimental setup
1. Patterns / photonic lattice
2. Setup
3. Results
4. Conclusions
CAM
9
=
1. Patterns / photonic lattice
2. Setup
3. Results
4. Conclusions
Results
1D Lattice Beam
Pattern Beam
Lattice k vector
+Pattern
k vector
k space
Lattice Bragg plane
MirrorPhotorefractive
crystal
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Results
1. Patterns / photonic lattice
2. Setup
3. Results
4. Conclusions
1. Pattern beam intensity above threshold and fixed lattice periodicity ( kL = 2 kP )
2. Pattern beam intensity below threshold with fixed lattice intensity (arbitrary lattice periodicity)
1D lattice 2D lattice
Forcing ?
Bragg / bandgap effect ?
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Results
1. Patterns / photonic lattice
2. Setup
3. Results
4. Conclusions
Iin
Ihex
Hexagonal pattern threshold
Pattern formation with and without lattice
(lattice intensity fixed)
Hexagonal pattern
formation without lattice
Hexagonal pattern
formation with 1D lattice
Bragg effect
Forcing
k L =
2 k P
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Conclusions
We have experimentally studied the possibility to control
a pattern by an optically induced photonic lattice
• Pattern
• Photonic lattice
• Photorefractive BaTiO3 in single feedback configuration
• External periodic illumination to create a virtual photonic crystal inside the BaTiO3
We have provided a rapid survey of different concepts
We have observed 2 different behaviors which may be
due to :
1. Patterns / photonic lattice
2. Setup
3. Results
4. Conclusions
• Bandgap effect
• Forcing
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Thank you for your attention !