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 Control of pattern formation in a single
feedback system by photonic bandgap structures 
Nicolas Marsal, Germano Montemezzani, Delphine
Wolfersberger, Marc Sciamanna Lab. Matériaux
Optiques, Photonique et Systèmes (CNRS - UMR
7132) Université Paul Verlaine - Metz and SUPELEC
France Dragomir Neshev Nonlinear Physics Centre,
Research School of Physical Sciences and
Engineering, Australian National University,
Canberra, Australia

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Outline

• Introduction to pattern and photonic lattice
• 2. Our experimental setup
• 3. Results
• 4. Conclusions

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• Pattern

Nonlinear medium
Free propagation
Photorefractive crystal, Kerr
1. Patterns / photonic lattice 2. Setup 3.
Results 4. Conclusions
Mirror
Single feedback
Liquid-crystal light valves (LCLV),
Photorefractive crystal, Na vapors
Active medium
Linear cavity
Lasers
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• Pattern properties

• Light structures spatially modulated and
  correlated
• Generated thanks to noise and modulation
  instability
• Disordered or ordered geometry

1. Patterns / photonic lattice 2. Setup 3.
Results 4. Conclusions
Goal
Control of pattern
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• Pattern control

C. Denz, Ann. Phys. (Leipzig) 13, 391 (2004)
1. Patterns / photonic lattice 2. Setup 3.
Results 4. Conclusions
C. Denz, Phys. Rev. Let. 81, 1614 (1998)
A.V. Mamaev, M. Saffman, Europhys. Lett. 34, 669
(1996)
And with a photonic lattice
?
R. Neubecker and A. Zimmermann, Phys. Rev. E 65,
035205 (2002)
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• Photonic lattice

Periodic illumination ( lattices or
light interferences )

• Periodic variation of the refractive index inside
  the medium

Light sensitive medium ( photorefractive
crystal )
Properties
2p / a
1. Patterns / photonic lattice 2. Setup 3.
Results 4. Conclusions
k space

• photonic crystal

a

• Light induced photonic crystal

Bandgap effect
Periodic refractive index
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• Experimental setup

Pattern control by a photonic lattice
Goal
Photorefractive BaTiO3 crystal
Mirror
1. Patterns / photonic lattice 2. Setup 3.
Results 4. Conclusions
Far field (k space)
External periodic illumination
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• Experimental setup

Horizontal polarization
M Mirror
? 532
M
BS Beam Splitter
LASER
HWP Half Wave Plate
HWP
BSP
BS
BSP Polarizing Beam Splitter
L Lens
SF Spatial Filter
LA Linear Atenuator
PC Photorefractive Crystal
1. Patterns / photonic lattice 2. Setup 3.
Results 4. Conclusions
Vertical polarization
VM Virtual Mirror
Pattern beam
Lattice beam
Feedback loop
4f system
Lattice
L1
SF
L2
f
f2
f
f2
L3
VM
L4
PC
LA
2f
2f
Far Field
CAM
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• Results

1D Lattice Beam
Photorefractive crystal
Mirror
Pattern Beam
1. Patterns / photonic lattice 2. Setup 3.
Results 4. Conclusions

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• Results

1. Pattern beam intensity above threshold and
fixed lattice periodicity ( kL 2 kP )
Bragg / bandgap effect ?
1. Patterns / photonic lattice 2. Setup 3.
Results 4. Conclusions
2. Pattern beam intensity below threshold with
fixed lattice intensity (arbitrary lattice
periodicity)
Forcing ?
1D lattice
2D lattice
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• Results

Pattern formation with and without
lattice (lattice intensity fixed)
Ihex
1. Patterns / photonic lattice 2. Setup 3.
Results 4. Conclusions
kL 2 kP
Bragg effect
Hexagonal pattern formation without lattice
Hexagonal pattern formation with 1D lattice
Forcing
Iin
Hexagonal pattern threshold
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• Conclusions

• We have provided a rapid survey of different
  concepts

• Pattern
• Photonic lattice

• We have experimentally studied the possibility
  to control
• a pattern by an optically induced photonic
  lattice

1. Patterns / photonic lattice 2. Setup 3.
Results 4. Conclusions

• Photorefractive BaTiO3 in single feedback
  configuration
• External periodic illumination to create a
  virtual photonic crystal inside the BaTiO3

• We have observed 2 different behaviors which may
  be
• due to

• Bandgap effect
• Forcing

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Thank you for your attention !