Preface	6
	Contents	8
	Contributors	10
	Chapter 1: Introduction to the Photorefractive Effect in Polymers	12
	1.1 Mathematical Model	15
	1.1.1 Charge Generation	15
	1.1.2 Charge Transport and Trapping	17
	1.1.3 Space-Charge Field	21
	1.1.4 Index Modulation	23
	1.1.4.1 Electro-Optic Effect	24
	1.1.4.2 Orientational Birefringence	26
	1.1.5 Diffraction Efficiency	27
	1.2 Components	28
	1.2.1 Polymer Matrices	29
	1.2.2 Chromophores	35
	1.2.3 Sensitizers	37
	1.2.4 Plasticizers	42
	1.3 Devices and Geometries	43
	1.4 Characterization	48
	1.4.1 Energy Levels	49
	1.4.2 Photogeneration Efficiency	50
	1.4.2.1 Xerographic Discharge	51
	1.4.2.2 DC Photocurrent	51
	1.4.3 Mobility	52
	1.4.3.1 Time of Flight	52
	1.4.3.2 Holographic Time of Flight	53
	1.4.3.3 Photoconductivity Dynamics	54
	1.4.4 Electro-Induced Refractive Index Change	56
	1.4.4.1 Interferometry	56
	AC Field	56
	1.4.4.2 Ellipsometry	57
	1.4.4.3 Electric Field Induced Second Harmonic Generation	57
	1.4.5 Two-Beam Coupling	59
	1.4.6 Four-Wave Mixing	63
	1.5 Conclusion	66
	References	67
	Chapter 2: Charge Transport and Photogeneration in Organic Semiconductors: Photorefractives and Beyond	75
	2.1 Introduction	75
	2.2 Basic Properties of Organic Semiconductors	78
	2.2.1 Organic Molecules	78
	2.2.2 Organic Solids	80
	2.3 Charge Transport and Photogeneration in Organic Semiconductors	81
	2.3.1 Semiconductors in Thermodynamic Equilibrium	82
	2.3.1.1 Electronic Structure	82
	2.3.1.2 Electronic Occupation	84
	2.3.2 Intrinsic Semiconductors	86
	2.3.3 Extrinsic Semiconductors	87
	2.3.3.1 Doping of Organic Semiconductors	87
	2.3.4 Semiconductors in Non-equilibrium: Charge Transport Models	88
	2.3.4.1 Quasi-Fermi Levels	89
	2.3.4.2 Drift-Diffusion Model	89
	2.3.4.3 Conductivity	91
	2.3.4.4 Equations of State	92
	2.3.5 Charge Transport in Organic Semiconductors	92
	2.3.5.1 Electronic Coupling	92
	2.3.5.2 Electron-Phonon Coupling	93
	2.3.5.3 Polaron Model: The Holstein Model	93
	2.3.5.4 Disorder Models	95
	2.3.6 Hopping Rate: Miller-Abrahams Model	95
	2.3.7 Hopping Rate: Marcus Model	96
	2.3.8 Poole-Frenkel Models	96
	2.3.9 Gaussian Disorder Model	97
	2.3.9.1 Influence of Randomly Oriented Dipoles	97
	2.4 Correlated Gaussian Disorder Model (CGDM): Energy Site Correlations	98
	2.5 Effective Medium Model: Polaron and Disorder Effects	99
	2.6 Extended Gaussian Disorder Model: Carrier Concentration Dependence	99
	2.7 Guest-Host Material Systems	101
	2.7.1 Photoconductivity in Organic Materials	101
	2.7.1.1 Approximations in the Context of Photorefractive Materials	104
	2.7.1.2 Exciton Dissociation	104
	2.7.1.3 Photogeneration in Intrinsic Photoconductors: Onsager Model	105
	2.7.1.4 Photogeneration in Extrinsic Photoconductors	106
	2.7.1.5 Empirical Approximations	107
	2.8 Recombination	108
	2.8.1 Langevin Recombination Theory	108
	2.8.1.1 Spatial Fluctuation in a Potential Landscape	110
	2.8.1.2 Trap-Assisted Recombination	110
	2.8.1.3 Multiple Trapping-Detrapping	111
	2.9 Photoconductivity and Space-Charge Field Formation in Photorefractive Polymers	111
	2.9.1 Space-Charge Field: Steady-State	111
	2.9.1.1 Space-Charge Field: Temporal Evolution	114
	2.10 Materials	116
	2.10.1 Extrinsic Photoconductors	117
	2.10.1.1 Sensitizers and Charge-Transfer Complexes	118
	2.10.1.2 Photoconductors for Photorefractive Applications I: Organic Sensitizers	119
	2.10.1.3 Photoconductors for Photorefractive Applications II: Inorganic Sensitizers	122
	2.10.2 Small-Molecule Semiconductors: Semicrystalline Materials and Molecular Glasses	124
	2.10.3 Donor-Acceptor Polymers	125
	References	127
	Chapter 3: Photorefractive Response: An Approach from the Photoconductive Properties	138
	3.1 Introduction	138
	3.2 Photoconduction	140
	3.2.1 Photocurrent Dynamics	141
	3.2.2 Photorefractive Response and Photoconductivity	145
	3.3 The Onsager Model	151
	3.4 Carrier Transport	153
	3.5 Measurements Methods	156
	3.5.1 Xerographic Discharge Method for Carrier Photogeneration [62, 63]	156
	3.5.1.1 Emission Limited Discharge Mode (ELD Mode)	158
	3.5.1.2 Space-Charge Limited Discharge Mode (SCLD Mode)	159
	3.5.2 A Time-of-Flight (TOF) Technique for Drift Mobility [64, 67, 68]	159
	3.5.2.1 Current Mode	160
	3.5.2.2 Voltage Mode	162
	3.6 Molecular and Device Engineering for Fast Response Photorefractive Polymer Composites	162
	3.7 Conclusion and Outlook	163
	References	163
	Chapter 4: Photorefractive Properties of Polymer Composites Based on Carbon Nanotubes	166
	4.1 Introduction	166
	4.2 Experimental	168
	4.3 Results and Discussion	170
	4.3.1 Photoelectric Properties	170
	4.3.2 Drift Mobility of Charge Carriers	173
	4.3.3 Third-Order Nonlinear Optical Properties	176
	4.3.4 Photorefractive Characteristics	180
	4.3.4.1 Photorefractive Effect at 1550nm	182
	4.3.4.2 Photorefractive Effect at 1064nm	185
	4.4 Conclusion	192
	References	193
	Chapter 5: Photorefractive Smectic Mesophases	196
	5.1 Introduction	196
	5.2 Thermotropic Mesophases: Orientational Order and Properties	198
	5.2.1 The Nematic Phase	199
	5.2.2 The Smectic A and C Phases	201
	5.2.3 Polymer Dispersed Liquid Crystals	206
	5.3 Photorefractivity in Chiral Smectic A Phases	207
	5.4 Photorefractivity in Chiral Smectic C Phases	211
	5.4.1 Initial Investigations	213
	5.4.2 Early Developments	214
	5.4.3 The Importance of Sample Orientation and Light Polarization	216
	5.4.4 Further Studies	220
	5.4.5 Bistable SmC* Devices	222
	5.5 Conclusions	228
	References	229
	Chapter 6: Inorganic-Organic Photorefractive Hybrids	232
	6.1 Introduction	232
	6.2 Inorganic-Organic Photorefractive Hybrids	234
	6.3 Conditions for Bragg-Matched Beam Coupling	236
	6.4 Methods to Improve Bragg-Matched Photorefractive Beam Coupling	243
	6.4.1 Cholesteric Liquid Crystal Photorefractive Hybrid Devices	243
	6.4.2 Ferroelectric Nanoparticle Doped Liquid Crystals for Photorefractive Hybrid Devices	245
	6.4.2.1 Understanding the Properties of Stressed Ferroelectric Nanoparticles	245
	6.4.2.2 Incorporation of Ferroelectric Nanoparticles in Inorganic-Organic Photorefractive Hybrid Devices	250
	6.5 Conclusions	253
	References	254
	Chapter 7: Wave Mixing in Photorefractive Polymers: Modeling and Selected Applications	257
	7.1 Introduction	257
	7.2 Induced Refractive Index in Steady State	259
	7.3 Wave Mixing in the Steady State: Transmission Geometry	263
	7.3.1 Steady State Theory	263
	7.3.2 Competition Between Gain and Beam Fanning in PR Polymer	267
	7.3.3 Other Effects: Gain vs. Incident Intensity, Higher Order Generation	270
	7.4 Selected Applications of Wave Mixing	272
	7.4.1 Real-Time Edge Enhancement	272
	7.4.2 Real-Time Edge-Enhanced Correlation	275
	7.4.3 Adaptive Filtering Using Four-Wave Mixing	279
	7.5 Transient Two-Wave Mixing: Role of Competing Charge Carriers	280
	7.6 Conclusions	285
	7.7 Epilogue and Acknowledgments	286
	References	287
	Chapter 8: Photorefractives for Holographic Interferometry and Nondestructive Testing	290
	8.1 Introduction	290
	8.2 Techniques for Holographic Metrology	291
	8.3 Considerations for Applicability of Holographic Metrology	294
	8.3.1 The Ideal Holographic Measurement Device	294
	8.3.2 Computation of Phase and Interpretation	296
	8.4 Photorefractive Materials for Holographic Interferometry	298
	8.4.1 Figures of Merit of Interest	298
	8.4.2 Photorefractive Materials Configurations of Interest	300
	8.5 Experiments and Industrial System with PR Materials for Nondestructive Testing	302
	8.5.1 Laboratory Experiments	302
	8.5.2 Compact Holographic Camera Based on Sillenite Crystal and Its Applications	307
	8.6 Discussion: Potential of Organic PR Materials	314
	8.7 Conclusions	315
	References	316
	Index	320