In 1988 physicists and chemists commemorated the centenary of the discovery of the first liquid crystals. Fora long period after this discovery, although many significant results were found, liquid crystal research remained a marginal topic of condensed matter physics. The situation changed in the sixties. At that time the remarkable electro-optical properties of liquid crystals were recognized and found soon widespread application in numeric displays. From a more fundamental point of view, the interest in disordered systems. increased in general at the same time. Liquid crystals represented an important dass of such systems. Among others, phase transitions, hydrodynamics and topological defects occurring in them attracted considerable attention. The connection between the liquid-crystalline state and the structure of biological membranes stimulated a Iot of works also. In the present volume we discuss a relatively new and rapidly developing branch of the fi. eld, namely nonlinear optical effects in liquid crystals. Optical studies have always played a signifi. cant role in liquid crystal science. Research of optical nonlinearities in liquid crystals began at the end of the sixties. Since then it became a powerful tool in the investigation of symmetry properties, interfacial phenomena or dynamic behaviour. Furthermore, several new aspects of nonlinear processes were demonstrated and studied extensively in liquid crystals. The subject covered in this book is therefore of importance both for liquid crystal research and for nonlinear optics itself. The term "nonlinear optics" is used here in a broad sense.

Inhalt
Liquid Crystals: Phases and Basic Properties.- Rotatory Power and Other Optical Properties of Certain Liquid Crystals, Acta Cryst. (1951).- Reflection and Trasmission by Single-Domain Cholesteric Liquid Crystal Films: Theory and Verification, Mol. Cryst. Liq. Cryst. (1970).- Light Propagation in Anisotropic Stratified Media in the Quasi Adiabatic Limit, Mol. Cryst. Liq. Cryst. (1987).- Pseudo-Stokes Parameter Representation of Light Propagation in Layered Inhomogeneous Uniaxial Media in the Geometric Optics Approximation, J. Opt. Soc. Am. (1987).- Study of Phase-Matched Normal and Umklapp Third-Harmonic Generation Processes in Cholesteric Liquid Crystals, Phys. Rev. A (1972).- Optical Second Harmonic Generation in Various Liquid Crystalline Phases, Mol. Cryst. Liq. Cryst. (1983).- Phase-Syncronous Optical Second Harmonic Generation in a Ferroelectric Liquid Crystal, Sov. Phys. JEPT (1984).- The Orientational Mechanics of Nonlinearity and the Self-Focusing of He-Ne Laser Radiation in Nematic Liquid Crystal Mesophases (Theory and Experiment), Optics Comm. (1981).- The Effects of an Optical Field on the Nematic Phase of the Liquid Crystal OCBP, JEPT Lett. (1980).- Optical-Field-Lnduced Birefringence and Freedericksz Transition in a Nematic Liquid Crystal, Phys. Rev. Lett. (1981).- Fredericks Transitions Induced by Light Fields, Sov. Phys. JEPT (1981).- The Influence of the Finite Size of the Light Spot on the Laser Induced Reorientation of Liquid Crystals, Mol. Cryst. Liq. Cryst. (1982).- Nonlocal Radial Dependence of Laser Induced Molecular Reorientation in a Nematic Liquid Crystal: Theory and Experiment, J. Opt. Soc. Am. B (1987).- Reorientation of Liquid Crystals by Superposed Optical and Quasistatic Electric Fields, Mol. Cryst. Liq. Cryst. (1982).- External Field Enhanced Optical Bistability in Nematic Liquid Crystals, Appl. Phys. Lett. (1985).- Observation of Optical Field Induced First-Order Electric Freedericksz Transition and Electric Bistability in a parallel Aligned Nematic Liquid-Crystal film, Appl. Phys. Lett. (1988).- Undamped Oscillations of NLC Director in the Field of an Ordinary Light Wave, Sov. Phys. JEPT (1984).- Collective Rotation of Molecules Driven by the Angular Momentum of Light in a Nematic Film, Phys. Rev. Lett. (1986).- Enhanced Nonlinear Birefringence in Hybrid Aligned Nematics, Appl. Phys. Lett. (1982).- Interaction of Light Waves with Nonuniformly Oriented Liquid Crystals, Sov. Phys. JEPT (1986).- Orientational Effects of an Ordinary Wave on a Nematic with a Hybrid Orientation, Sov. J. Quantum Electron. (1987).- Optically Induced Twist Freedericksz transitions in Planar-Aligned Nematic Liquid Crystal, Phys. Rev. A (1987).- Optically Induced Molecular Reorientation in a Smetic-C Liquid Crystal, Phys. Rev. A (1984).- Transient Laser-Induced Molecular Reorientation and Laser Heating in a Nematic Liquid Crystal, Phys. Rev. A (1984).- Nonlinear Optical Effects in the Nematic Phase, Mol. Cryst. Liq. Cryst. (1985).- Dynamic Gratings and the Associated Self Diffractions and Wavefront Conjugation Processes in Nematic Liquid Crystals, IEEE J. Quantum Electron. (1986).- All-Optical Bistability in Nematic Liquid Crystal at 20 ?W Power Levels, Appl. Phys. Lett. (1988).- Photostimulated Cange of Phase-Transition Temperature and Giant Optical Nonlinearity of Liquid Crystals, Sov. Phys. JEPT (1983).