Iam-Choon Khoo - Liquid Crystals

1 Cover

2 Title Page

3 Copyright Page

4 Preface

5 1 Introduction to Liquid Crystals 1.1. MOLECULAR STRUCTURES AND CHEMICAL COMPOSITIONS 1.2. OPTICAL PROPERTIES 1.3. LYOTROPIC, POLYMERIC, AND THERMOTROPIC LIQUID CRYSTALS 1.4. MIXTURES, POLYMER‐DISPERSED, AND DYE‐DOPED LIQUID CRYSTALS 1.5. LIQUID CRYSTAL CELLS FABRICATION REFERENCES

6 2 Order Parameter, Phase Transition, and Free Energies2.1. BASIC CONCEPTS 2.2. MOLECULAR INTERACTIONS AND PHASE TRANSITIONS 2.3. MOLECULAR THEORIES AND RESULTS FOR THE LIQUID CRYSTALLINE PHASE 2.4. ISOTROPIC PHASE OF LIQUID CRYSTALS REFERENCES

7 3 Nematic Liquid Crystals3.1. INTRODUCTION 3.2. ELASTIC CONTINUUM THEORY 3.3. DIELECTRIC CONSTANTS AND REFRACTIVE INDICES 3.4. OPTICAL DIELECTRIC CONSTANTS AND REFRACTIVE INDICES 3.5. FLOWS AND HYDRODYNAMICS 3.6. FIELD‐INDUCED DIRECTOR AXIS REORIENTATION EFFECTS REFERENCES

8 4 Cholesteric, Smectic, and Ferroelectric Liquid Crystals4.1. CHOLESTERIC LIQUID CRYSTALS 4.2. OPTICAL PROPERTIES OF CHOLESTERICS 4.3. CHOLESTERIC BLUE PHASE LIQUID CRYSTALS 4.4. SMECTIC AND FERROELECTRIC LIQUID CRYSTALS: A BRIEF SURVEY References

9 5 Light Scattering5.1. INTRODUCTION 5.2. ELECTROMAGNETIC FORMALISM OF LIGHT SCATTERING IN LIQUID CRYSTALS 5.3. SCATTERING FROM DIRECTOR AXIS FLUCTUATIONS IN NEMATIC LIQUID CRYSTALS 5.4. LIGHT SCATTERING IN THE ISOTROPIC PHASE OF LIQUID CRYSTALS 5.5. TEMPERATURE, WAVELENGTH, AND CELL GEOMETRY EFFECTS ON SCATTERING 5.6. SPECTRUM OF LIGHT AND ORIENTATION FLUCTUATION DYNAMICS 5.7. RAMAN SCATTERINGS 5.8. BRILLOUIN AND RAYLEIGH SCATTERINGS 5.9. A BRIEF INTRODUCTION TO NONLINEAR LIGHT SCATTERING REFERENCES

10 6 Liquid Crystals Optics and Electro‐optics6.1. INTRODUCTION 6.2. REVIEW OF ELECTRO‐OPTICS OF ANISOTROPIC AND BIREFRINGENT CRYSTALS 6.3. ELECTRO‐OPTICS OF NEMATIC LIQUID CRYSTALS 6.4. NEMATIC LIQUID CRYSTAL SWITCHES FOR DISPLAY APPLICATION 6.5. ELECTRO‐OPTICAL EFFECTS IN OTHER PHASES OF LIQUID CRYSTALS 6.6. NON‐DISPLAY APPLICATIONS OF LIQUID CRYSTALS References

11 7 Optical Propagation in Anisotropic Materials7.1. ELECTROMAGNETIC FORMALISMS FOR OPTICAL PROPAGATION 7.2. POLARIZED LIGHT PROPAGATION IN LIQUID CRYSTAL DISPLAY PANEL 7.3. EXTENDED JONES MATRIX METHOD 7.4. FINITE‐DIFFERENCE TIME‐DOMAIN TECHNIQUE 7.5. NONLINEAR LIGHT PROPAGATION IN LIQUID CRYSTALS – A FIRST LOOK 7.6. SYSTEMS OF UNITS References

12 8 Laser‐induced Reorientation Nonlinear Optical Effects8.1. INTRODUCTION 8.2. LASER‐INDUCED MOLECULAR REORIENTATIONS IN THE ISOTROPIC PHASE 8.3. MOLECULAR REORIENTATIONS IN THE NEMATIC PHASE 8.4. NEMATIC PHASE REORIENTATION DYNAMICS 8.5. LASER‐INDUCED DIRECTOR AXIS REALIGNMENT IN DYE‐DOPED LIQUID CRYSTALS 8.6. DC FIELD AIDED OPTICALLY INDUCED NONLINEAR OPTICAL EFFECTS IN LIQUID CRYSTALS – PHOTOREFRACTIVITY 8.7. REORIENTATION IN OTHER PHASES OF PRISTINE (UNDOPED) LIQUID CRYSTALS REFERENCES

13 9 Thermal, Density, Lattice Distortion Optical Nonlinearities in Nematic, Cholesteric, and Blue‐phase Liquid Crystals9.1. INTRODUCTION 9.2. ELECTROSTRICTION AND FLOWS IN NON‐ABSORBING LIQUID CRYSTALS – A GENERAL OVERVIEW 9.3. LASER‐INDUCED DENSITY AND TEMPERATURE MODULATIONS IN LIQUID CRYSTALS 9.4. OPTICAL NONLINEARITIES OF NEMATIC LIQUID CRYSTALS 9.5. COUPLED NONLINEAR OPTICAL EFFECTS IN NEMATIC LIQUID CRYSTALS 9.6. NONLINEAR OPTICAL RESPONSES OF CHOLESTERIC BLUE‐PHASE LIQUID CRYSTALS REFERENCES

14 10 Electronic Optical Nonlinearities10.1. INTRODUCTION TO QUANTUM MECHANICAL TREATMENT OF MOLECULES 10.2. DENSITY MATRIX FORMALISM FOR OPTICAL INDUCED MOLECULAR ELECTRONIC POLARIZABILITIES 10.3. LINEAR AND NONLINEAR ELECTRONIC SUSCEPTIBILITIES 10.4. INTENSITY‐DEPENDENT REFRACTIVE INDEX CHANGE AND NONLINEAR ABSORPTION REFERENCES

15 11 Nonlinear Optics11.1. INTRODUCTION 11.2. COUPLED MAXWELL WAVE EQUATIONS 11.3. NONLINEAR OPTICAL PHENOMENA 11.4. STIMULATED SCATTERINGS 11.5. ULTRAFAST LASER PULSE SELF‐ACTION EFFECTS IN CHOLESTERIC LIQUID CRYSTALS REFERENCES

16 12 Nonlinear Optical Processes Observed in Liquid Crystals 12.1. SELF‐ACTION NONLINEAR OPTICAL PROCESSES 12.2. OPTICAL WAVE MIXINGS 12.3. LIQUID CRYSTALS FOR ALL‐OPTICAL IMAGE PROCESSING 12.4. HARMONIC GENERATIONS AND SUM‐FREQUENCY SPECTROSCOPY 12.5. OPTICAL SWITCHING 12.6. NONLINEAR ABSORPTION AND OPTICAL LIMITING OF LASERS FOR EYE/SENSOR PROTECTION References

17 Index

18 End User License Agreement

1 Chapter 1 Table 1.1 Anisotropic Physical Parameters of a Typical Nematic Liquid Crystals (E...

2 Chapter 7TABLE 7.1 Physical constant and their values in SI (MKS) units.

3 Chapter 8TABLE 8.1 Orientational nonlinearity of liquid crystals near T c.

4 Chapter 9TABLE 9.1 Typical Values for Some Nematic Liquid Crystals

5 Chapter 12TABLE 12.1 Refractive index coefficients of some nonlinear optical materials.TABLE 12.2 Switching efficiency (χ (3)/ατ) of some nonlinear optical materials....Table 12.3 Comparison of the performance characteristics of commercial LCSLM with...Table 12.4 CW and pulsed lasers.

1 Chapter 1 Figure 1.1. Molecular structure of a typical liquid crystal. Figure 1.2. Molecular structure of a heterocyclic liquid crystal. Figure 1.3. Molecular structure of an organometallic liquid crystal. Figure 1.4. Molecular structure of a sterol. Figure 1.5. Molecular structure of 5CB (pentyl cyanobiphenyl). Figure 1.6. The π → π *electronic transitions in a benzene molecule. Figure 1.7. Transmission spectra of nematic liquid crystals: (a) 5CB; (b) N ‐... Figure 1.8. Chemical structure and cartoon representation of sodium dodecyl ... Figure 1.9. Three different types of polymeric liquid crystals: (a) vinyl ty... Figure 1.10. Polymeric liquid crystals: (a) main chain; (b) side chain. Figure 1.11. Self‐organization of the rod‐shaped LC molecules via local and ... Figure 1.12. Arrangement of dipoles in the centrosymmetric bulk crystal such... Figure 1.13. Molecular arrangements of liquid crystals: (a) smectic‐A; (b) s... Figure 1.14. A shuttlecock‐shaped liquid crystal formed by incorporating ful... Figure 1.15. Molecular structures of the four constituents making up the liq... Figure 1.16. Phase diagram of the mixture of two liquid crystals. Figure 1.17. Alignment of a dichroic dye‐doped nematic liquid crystal: (a) b... Figure 1.18. Schematic depiction of a polymer‐dispersed liquid crystal mater... Figure 1.19. Nematic liquid crystal cells: (a) homeotropically aligned; (b) ... Figure 1.20. (a) CLC with focal conic structure as a result of director axis... Figure 1.21. Left: Image of logo obstructed by a thin CLC cell with focal co... Figure 1.22. Schematic depiction of the makeup of a blue-phase liquid crysta... Figure 1.23. Reflectance from BPLC in polycrystalline (lower photo) and sing... Figure 1.24. Tunable micro‐ and nano‐photonic structures incorporating liqui... Figure 1.25. Immobile LC layer around a plasmonic nanostructure (not drawn t... Figure 1.26. Schematic of a focused laser propagating through the guiding (l... Figure 1.27. A capillary filled with dye‐doped BPLC core for random laser ac...

2 Chapter 2 Figure 2.1. Coordinate system defining the microscopic order parameter of a ... Figure 2.2. Schematic depiction of the numerical solution of the two transce... Figure 2.3. (a) Observed oscilloscope trace of the diffracted signal in a dy... Figure 2.4. Observed buildup times of the diffracted signal associated with ... Figure 2.5. Schematic depiction of the molecular levels involved in ground e... Figure 2.6. Free energies F ( Q ) for different temperatures T . At T = T c, ∂

3 Chapter 3 Figure 3.1. (a) Twist deformation in a nematic liquid crystal; (b) splay def... Figure 3.2. A homeotropic nematic liquid crystal with strong surface anchori... Figure 3.3. Soft‐boundary condition. The applied field will reorient both th... Figure 3.4. Dispersion data of the dielectric constant ε ||and ε Figure 3.5. Dispersion data of the dielectric constant ε ||and ε Figure 3.6. Measured birefringence De = ε ||− ε ⊥of three ... Figure 3.7. (a) Temperature dependence of the refractive indices of 5CB in t... Figure 3.8. Plot of dn ||/ dT and dn ⊥/ dT for the liquid crystal for te... Figure 3.9. An elementary volume of fluid moving at velocity v ( r , t ) in spa... Figure 3.10. Stresses acting on opposite planes of an elementary volume of f... Figure 3.11. Sheer flow in the presence of an applied magnetic field. Figure 3.12. Pure twist deformation induced by an external magnetic field H ... Figure 3.13. Director axis reorientation causing flows.