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Polarization Engineering throughNanoengineered Morphology
Akhlesh Lakhtakia
Department of Engineering Science and Mechanics
The Pennsylvania State University
March 11, 2008Faculty of EngineeringMultimedia UniversityCyberjaya, SelangorMalaysia
Optics Practice
Control of– Intensity– Operating frequency band– Polarization state
Optics Practice
Long History– Intensity– Operating frequency band
Short History– Polarization state
Optics Practice
Polarization – Discovered in 1809
Etienne-Louis Malus 1775 - 1812
Optics PracticePolarization – Discovered in 1809
– “Do not disturb” designs
Etienne-Louis Malus 1775 - 1812
Polarization Engineering
– Anisotropic materials– Uniaxial and biaxial crystals– Piezoelectric materials
– Bianisotropic materials– Chiral materials– Magnetoelectric materials
Polarization Engineering
– Anisotropic materials– Bianisotropic materials
SPIE Press (2003)
Polarization Engineering
– Sculptured Thin Films
SPIE Press (2005)
Students & Collaborators
• Joseph Sherwin, Sean Pursel, Benjamin Ross, Fei Wang (Penn State)
• Mark Horn, Jian Xu (Penn State)• Ian Hodgkinson (Otago)• John Polo (Edinboro)• Juan Adrian Reyes (UNAM, Mexico)
Outline
• Introduction• Optical Modeling• Examples of Polarization Engineering• More Examples• Electrical Control
INTRODUCTION
Sculptured Thin Films
Assemblies of Parallel Curved Nanowires/Submicronwires
Controllable Nanowire Shape
2-D - nematic3-D - helicoidal
combination morphologies
Sculptured Thin Films
Assemblies of Parallel Curved Nanowires/Submicronwires
Controllable Nanowire Shape
2-D - nematic3-D - helicoidal
combination morphologiesvertical sectioning
Sculptured Thin FilmsAssemblies of Parallel Curved Nanowires/Submicronwires
Controllable Nanowire Shape
2-D - nematic3-D - helicoidal
combination morphologiesvertical sectioning
Nanoengineered Materials (1-3 nm clusters)
Controllable Porosity (10-90 %)
Sculptured Thin FilmsAntecedents:
(i) Young and Kowal - 1959
(ii) Niuewenhuizen & Haanstra - 1966
(iii) Motohiro & Taga - 1989
Conceptualized by Lakhtakia & Messier (1992-1995)
Optical applications (1992- )
Biological applications (2003- )
Physical Vapor Deposition (Columnar Thin Films)
Physical Vapor Deposition (Sculptured Thin Films)
Rotate abouty axis fornematicmorphology
Rotate aboutz axis forhelicoidalmorphology
Mix and matchrotations forcomplexmorphologies
Physical Vapor Deposition(Serial Bideposition)
ξ (axis 2)
χv (axis 1)
SnO2
Adapted for STFs by Hodgkinson
Sculptured Thin FilmsOptical Devices: Polarization Filters
Bragg FiltersUltranarrowband FiltersFluid Concentration SensorsBacterial Sensors (Penn State)Light Sources (Penn State)
Biomedical Applications: Tissue Scaffolds (Penn State)Stents (Penn State)Bone Repair (Penn State)
Other Applications: Photocatalysis (Toyota)Thermal Barriers (Alberta)Energy Harvesting (Penn State, Toledo)
Toledo)
OPTICAL MODELING
Optical Modeling of STFs
LinearBianisotropic Materials
SPIE Press (2003)
Optical Modeling of STFs
LinearBianisotropic Materials
SPIE Press (2003)
Optical Modeling of STFsDielectric Materials
Optical Modeling of STFsLocally Orthorhombic Materials
Optical Modeling of STFsHomogenize a collectionofparallel ellipsoidsto get
Sherwin and Lakhtakia (2001-2003): Bruggeman formalism
Mathematica Program
Optical Modeling of STFsWave Propagation
Mathematica Program
EXAMPLES OF POLARIZATION ENGINEERING
Chiral Sculptured Thin Films
Chiral STFs: Circular Bragg Phenomenon
A simple explanation (Coupled-Wave Theory):
• Co-handed wave: Scalar Bragg grating
• Cross-handed wave: Homogeneous bulk medium
Chiral STF as CP Filter
Chiral STF as CP FilterEngineering of Bragg Regime and CP State
Chiral STF as CP Filter
Rotational Speed: Controls
Rotational Sense: Controls
Vapor Incidence Angle: Controls
Engineering of Bragg Regime and CP State
Chiral STF as CP FilterPost-Deposition Engineering of Bragg Regime
Annealing before after
Chiral STF as CP FilterPost-Deposition Engineering of Bragg Regime
Annealing
Blue-shift factors:(i) Decreases pitch(ii) Thins nanowires
Red-shift factors:(i) Increases permittivity
Blue-shifton annealing
Spectral Hole Filter
Central Phase Defect in a Chiral STF
- Homogeneous-layer defect- Isotropic- Anisotropic
- Twist defect
- Structurally-chiral-layer defect
Spectral Hole Filter
Spectral Hole Filter
Spectral Hole Filter
Spectral Hole Filter
Defect-free
Spectral Hole Filter
Defect-free
With defect
Thin Chiral STF Thick Chiral STFReflection Hole Transmission HoleCo-handed Cross-handedTheory/Experiment Theory only
Spectral Hole FilterIsotropic-layer defect
Spectral Hole FilterTwist defect
Spectral Hole FilterPost-Deposition Engineering
Chemical Etching
Blue-shift
Pursel, Lakhtakia, and Horn, Opt. Eng. 45 (2007), 040507
Spectral Hole FilterPost-Deposition Engineering
Chemical Etching Columnar Thinning Blue Shift
Pursel, Lakhtakia, and Horn, Opt. Eng. 45 (2007), 040507
Fluid Concentration Sensor
MOREEXAMPLES OF POLARIZATION ENGINEERING
Tilt-Modulated Chiral STF
Tilt-Modulated Chiral STFOrdinary Dielectric Mirror
Advantages:
(1) Single material
(2) Bragg FWHM governed by tilt-modulation amplitude
Ambichiral STFReusch 1869
Ambichiral STF
All layers ofequal thickness.
2 Bragg regimes
Different CP statesreflected
Bragg L
Bragg R
Left-handed structure
Ambichiral STF
Layers ofunequal thickness.
1 Bragg regime
Ambichiral STF
Layers ofunequal thickness.
1 Bragg regime
EP states (and ) reflected
Better for CP and nearly CP states
ELECTRICALCONTROL
ofCIRCULAR BRAGG
PHENOMENON
ELECTRICALLY CONTROLLED CBP
ELECTRICALLY CONTROLLED CBP
DC voltage across the thickness
ELECTRICALLY CONTROLLED CBP
Normal incidence
ELECTRICALLY CONTROLLED CBP
Without dc voltage With dc voltage
ELECTRICALLY CONTROLLED CBP
Without dc voltage
Pseudo-IsotropicPoint
ELECTRICALLY CONTROLLED CBP
Without dc voltage With dc voltage
Pseudo-IsotropicPoint
ELECTRICALLY CONTROLLED CBP
Without dc voltage With dc voltage
Pseudo-IsotropicPoint
Further Studies
Electrically Controlled CBP
DC voltage can enhance local linear birefringence Thinner CP filters
Normal incidence
Electrically Controlled CBP
Oblique incidence
Electrically Controlled CBP
Without dc voltage With dc voltage
Electrically Controlled CBP
Without dc voltage With dc voltage
Electrically Controlled Narrowband CP Filters: Reflection Holes
Incorporate a Central 90-deg-twist defect
Without dc voltage
L = 30
AmmoniumDihydrogenPhosphate
Normal incidence
Lakhtakia, Asian J. Phys. 15 (2006) 275-282
Electrically Controlled Narrowband CP Filters: Reflection Holes
Incorporate a Central 90-deg-twist defect
With dc voltage
L = 16
AmmoniumDihydrogenPhosphate
Normal incidence
Lakhtakia, Asian J. Phys. 15 (2006) 275-282
Electrically Controlled Ultranarrowband CP Filters: Transmission Holes
Incorporate a Central 90-deg-twist defect
Without dc voltage
L = 180
AmmoniumDihydrogenPhosphate
Normal incidence
Lakhtakia, Asian J. Phys. 15 (2006) 275-282
Electrically Controlled Ultranarrowband CP Filters: Transmission Holes
Incorporate a Central 90-deg-twist defect
With dc voltage
L = 58
AmmoniumDihydrogenPhosphate
Normal incidence
Lakhtakia, Asian J. Phys. 15 (2006) 275-282
Electrically Controlled CBP: Ambichiral Structure
Continuous spiral replaced by stepped spiral60-deg (or less) steps!
Electrically Controlled CBP: Ambichiral Structure
RCP rejection LCP rejection
Without dc voltage
AmmoniumDihydrogenPhosphate
Normal incidence
Electrically Controlled CBP: Ambichiral Structure
With dc voltage
Normal incidence
RCP rejection LCP rejection
AmmoniumDihydrogenPhosphate
More General Studies
Electrically Controlled CBP
(Local) point group symmetries:
Isotropic 2 classes
Uniaxial 13 classes
Biaxial 5 classes
Electrically Controlled CBP
Electrically Controlled CBP
Oblique incidence
Electrically Controlled CBP
Electrically Controlled CBPIsotropic (zinc telluride)
Without dc voltage
Withdc voltage
Electrically Controlled CBPUniaxial (lithium niobate)
Without dc voltage
Withdc voltage
Electrically Controlled CBPBiaxial (potassium niobate)
Without dc voltage
Withdc voltage
Tunable UltranarrowbandCP Filters: Transmission Holes
Tunable UltranarrowbandCP Filters: Transmission Holes
Uniaxial (lithium niobate)
Central 90-deg-twist defect
Tunable UltranarrowbandCP Filters: Transmission Holes
Biaxial (potassium niobate)
Central 90-deg-twist defect
Electrically Controllable CBP
Electrically Controllable CBP
Towards a nano-to-continuum control model
Thesis
Morphology can be nanoengineered
to obtain
desired polarization&
operating frequency band
ThankYou