Ferroelectric Crystals for Photonic Applications (eBook)

Pietro Ferraro,  is chief research scientist of the Research Group on Diagnostic methods, interferometry and microscopy at INOA-CNR. He has been Principal Investigator with Alenia Aeronautics (1989-1993). He published more then 90 papers in Archivial Journals, 3 book chapters and has 10 patents and presented more then 150 papers at International Conferences, being invited speaker several times. He was Guest Editor of 5 special issues on international journals and is member of the Editorial Board of the Optics and Lasers in Engineering (Elsevier). He chaired two international conferences and served as member of scientific committee in many conferences. Among his current scientific interests are: holography, interferometry, microscopy, fabrication of nanostructures, ferroelectric crystals, optical fiber sensors.Simonetta Grilli got her PhD at the Royal Institute of Technology in Stockholm and she is currently a research scientist at the INOA-CNR (Italy). She has been invited as plenary speaker at the Photonics Europe SPIE Conference. She has published more than 20 papers in International Journals and she has had two patents awarded. Her currents research interests include: nanoscale domain engineering and surface structuring in ferroelectric crystals; interferometric analysis of ferroelectric properties; digital holography microscopy; super-resolution; tunable photonic devices.Paolo De Natale is research director at INOA and, since 2001, he has been directing the INOA section in Pozzuoli, Naples, Italy. He has authored more than 120 papers, published in peer-reviewed international journals and books, is co-inventor in 3 patents and has given invited and plenary lectures in many International Conferences. His present research interests include: nonlinear optics, laser physics, atomic and molecular high precision spectroscopy, nonlinear interactions in ferroelectric crystals, frequency metrology, micron and nano engineering of ferroelectric crystals, environmental monitoring with optical devices, optical sensors and diagnostics, physics of non-linear optical crystals, development of infrared coherent sources.

Preface 6
Contents 8
List of Contributors 16
Part I Fabrication 21
Micro-Structuring and Ferroelectric Domain Engineering of Single Crystal Lithium Niobate 22
Introduction 22
Other Methods 23
Differential Chemical Etching 24
z-Faces 24
y-Faces 28
Microstructures 30
Summary and Future Work 36
References 37
Fabrication and Characterization of Self-Assembled Ferroelectric Linear and Nonlinear Photonic Crystals: GaN and LiNbO3 40
Introduction 40
Micro-Domain Engineering with Conventional Poling Electrode Design 42
Internal Field Effect in the Poling of Congruent-Grown LiNbO3 or LiTaO3 42
Origin of the Fringe Field 43
Poling Issues with Doped or Stoichiometric LiNbO3 and LiTaO3 45
From Micron to Submicron Domain Engineering with Improved Electrode Design 46
Charged Potential Barrier Method 46
Stack of High-k Dielectric Poling Electrode Method 55
Submicron Domain Engineering with Self-Assembly Type of Poling Electrodes 59
Submicron Domain Engineering in Ferroelectric Semiconductors 63
Conclusion 66
References 67
Sub-Micron Structuring of LiNbO3 Crystals with Multi-Period and Complex Geometries 72
Introduction 72
Overview of the Etching Techniques Applied to Lithium Niobate 72
Electric Field Poling and Overpoling 78
Holographic Lithography 80
Periodic Sub-Micron Structuring 82
Overpoling Applied to One-Dimensional Michelson Resist Gratings 82
Overpoling Applied to Two-Dimensional Michelson Resist Gratings 84
Overpoling Applied to Two-Beams Resist Gratings at Sub-Micron Scale 85
Complex Surface Structures by Moiré HL 86
Double-Face Sub-Micron Surface Structures 91
Possible Applications for Novel Photonic Crystal Devices 92
References 95
Nonlinear Optical Waveguides in Stoichiometric Lithium Tantalate 98
Material Properties 100
Physical Properties 100
Optical Properties 102
Waveguide Fabrication through Reverse-Proton-Exchange 104
Fabrication and Characterization Procedures 106
Modelling 107
Second-Harmonic Generation in RPE-PPSLT Waveguides 112
Highly Confining Waveguides 112
Weakly-Confining Waveguides 114
References 116
3-D Integrated Optical Microcircuits in Lithium Niobate Written by Spatial Solitons 120
Review of Waveguide Fabrication Techniques 120
Theory of Photorefractive-Photovoltaic Spatial Solitons in Biased LiNbO3 121
Photorefractive Model 121
Time Dependent Electric Field Distribution 122
PR Space Charge Field 123
Soliton Solutions 124
Dark Solitons 125
Bright Solitons 129
Photorefractive Bright Soliton Observation 131
Waveguiding in Soliton Channels/Strips 134
Experimental Observation 134
Fixing Soliton Waveguides and Circuits in Lithium Niobate Crystals 135
Waveguide Characteristics 136
Optical Microcircuits with Soliton Waveguides 136
Passive 136
Optical Microcircuits with Solitons Waveguides 138
Passive 138
Active 141
Three-Dimensional Optical Micro-Circuits with SWGs 148
References 151
Part II Characterization 154
Light Aided Domain Patterning and Rare Earth Emission Based Imaging of Ferroelectric Domains 156
Introduction and Background 156
Overview 156
Rare Earth Ions in LiNbO3 156
Combined Excitation Emission Spectroscopy 158
Confocal Microscopy and Spectroscopy 160
Application of RE Spectroscopy to the Imaging of Integrated Optical Devices in Lithium Niobate 162
Rare Earth Ions as Probes 163
Imaging of Waveguides 163
Imaging of Ferroelectric Domains and Domain Wall Regions 166
Imaging of Periodically Poled Waveguide Structures 170
Light Induced Domain Inversion 172
Methods 172
Build-Up of Charge under Focussed Laser Irradiation 173
Influence of Light on Domain Inversion and Growth 174
Direct Writing of Domain Patterns 177
Summary and Conclusions 181
References 182
Visual and Quantitative Characterization of Ferroelectric Crystals and Related Domain Engineering Processes by Interferometric Techniques 184
Introduction 184
Measuring the Refractive Indices and Thickness of Lithium Niobate Wafers 185
Visualization and In-Situ Monitoring of Domains Formation 190
Digital Holography and Experimental Configuration for In-Situ Investigation of Poling 193
Investigation of the Electro-Optic Effect and Internal Fields 211
Evaluation of Optical Birefringence at Ferroelectric Domain Wall in LiNbO3 220
References 223
New Insights into Ferroelectric Domain Imaging with Piezoresponse Force Microscopy 228
Introduction 228
Ferroelectrics 228
Lithium Niobate (LiNbO3) 229
Principles of Scanning Force Microscopy (SFM) 230
Tip-Cantilever-Surface Interactions 230
Cantilever Movements 231
Cross-Talk 232
Calibration 232
Principles of Piezoresponse Force Microscopy (PFM) 233
PFM Setup & Standard Settings
System-Inherent Background in PFM Measurements 235
Vectorial Description 235
Consequences of the System-Inherent Background 237
Background-Induced Misinterpretations 237
Background-Free PFM Imaging 239
Quantitative Piezoresponse Force Microscopy 240
Amplitude of the PFM Signal 240
Domain Wall Width 241
Ferroelectric Domain Imaging by Lateral Force Microscopy 242
Origin of the Lateral Signal 243
Application to PPLN 243
Conclusions 245
References 245
Structural Characterization of Periodically Poled Lithium Niobate Crystals by High Resolution X-Ray Diffraction 248
Introduction 248
The Principle of the XRD Technique 251
The Theory of High Resolution X-Ray Diffraction 252
The HRXRD Applied to PPLN Crystals 258
Experimental Set-Up for Structural Characterization by HRXRD 261
Applications 265
Investigation of Sub-Micrometric PPLN Crystals 265
Investigation of Micrometric PPLN Crystals with Bent Domain Walls 268
Conclusions 272
References 273
Part III Applications 276
Nonlinear Interactions in Periodic and Quasi-Periodic Nonlinear Photonic Crystals 278
Introduction 278
Wave Equations in NLPC 280
Analysis of a Periodic Nonlinear Photonic Crystal 282
The Real Lattice 282
The Reciprocal Lattice 284
Conversion Efficiency for Specific Types of 2D Periodic Structures 285
Analysis of a Quasi-Periodic Nonlinear Photonic Crystal 291
Statement of the Problem 291
Solution by Quasiperiodic Lattices 292
Establishing an Orthogonality Condition 293
Tiling the Quasi-Periodic Lattice by the Dual Grid Construction 294
The Fourier Transform of the Quasi-Periodic Lattice 295
From Lattice to a Nonlinear Photonic Crystal 296
A One-Dimensional Example - The Three Wave Doubler 297
Discussion and Summary 301
References 302
Domain-Engineered Ferroelectric Crystals for Nonlinear and Quantum Optics 304
Introduction 304
Classification of Nonlinear Processes 304
Phase Matching 305
Nonlinear Optics for Spectroscopic Applications 306
Coherent Sources for mid-IR Spectroscopy and Metrology 306
OFCS Extension to the mid-IR 307
Future Perspectives 314
Structured Nonlinear Crystals for Quantum Optics 315
Quantum Light Sources 316
Single-Photon Detectors 320
References 322
Photonic and Phononic Band Gap Properties of Lithium Niobate 326
Introduction 326
Photonic Crystals 328
Band Structure Theory and Slow Light 328
Fabrication and Examples 332
Experimental Procedure 333
Measurement of a PBG in a LN Photonic Crystal 337
LN PtC Waveguides: Transmission and SNOM Characterization 338
A LN PtC Intensity Modulator 340
Phononic Crystals 342
Theory 342
Fabrication and Examples 345
Conclusion 351
References 353
Lithium Niobate Whispering Gallery Resonators: Applications and Fundamental Studies 356
Introduction 356
Modulators 357
Principle of Operation 359
Performance 359
Tunable Filters 360
First-Order Filter 360
Third-Order Filter 361
Fifth-Order Filter 363
Insertion Loss 364
WGRs Made of Periodically Poled Lithium Niobate 365
Optical Frequency Doubling 366
Calligraphic Poling 369
Reconfigurable Filters 370
Photorefractive Damage 371
Congruent LiNbO3 373
Magnesium Doped Congruent LiNbO3 375
Crossings and Anticrossings of the Modes 377
Holographic Engineering of the WGM Spectra 378
Infrared Transparency and Photorefractivity of Lithium Niobate Crystals: Theory 378
Rate Equations 381
Solution of the Rate Equations 384
Absorption of the Light and Initial Concentration of the Filled Traps 387
Appendix A: Basic Properties of WGMs 390
Appendix B: Lithium Niobate Impurities: A Short Review of Existing Results 391
B.1 Small Polarons 392
B.2 Bipolarons 393
B.3 Iron 394
Appendix C: Photorefractivity in Red: A Short Review of the Existing Results 395
C.1 Light Induced Change of Refractive Index 395
C.2 Light Induced Change of Absorption 396
Appendix D: Numerical Values of the Basic Rates Characterizing the Impurities 396
References 399
Applications of Domain Engineering in Ferroelectrics for Photonic Applications 404
Introduction 404
Ferroelectrics and Domain Engineering 404
Applications of Domain Engineered Structures 406
Frequency Conversion 406
Electro-Optic Devices 409
Challenges of Domain Engineered Ferroelectric Devices 415
Conclusions 416
References 417
Electro-Optics Effect in Periodically Domain-Inverted Ferroelectrics Crystals: Principles and Applications 420
Introduction 420
Basic principle 421
Electro-Optic Effect in Crystals 421
Electro-Optical Effect for Crystals of 3 m Symmetry Group 423
Electro-Optical Effect in Periodically Domain-Inverted Crystals with 3 m Symmetry 426
Applications 432
Devices Based on Bragg Diffraction Grating Structure 432
Devices Based on Solc-Layered Structure 435
Other Application Devices 437
References 438
Index 440