Preface
Liquid crystal science and applications now permeate almost all segments
of the society—from large industrial displays to individual homes and offices.
Nondisplay applications in nonlinear optics, optical communication, and
data/signal/image processing are receiving increasing attention and are growing
at a rapid pace. Since the last edition (1995), tremendous progress has been
made in the study of optics of liquid crystals, and advances are measured by
orders of magnitude rather than small increments. Feature sizes have shrunk
from microns to nanometers; optical nonlinearities, such as the refractive index coefficient, have
“grown” a millionfold from 10-3 to 103 cm2/W. This book is intended to capture the essentials of
these fundamental breakthroughs and point out new exciting possibilities, while providing the
reader a basic overall grounding in liquid crystal optics.
This edition of Liquid Crystals, consisting of ten original book chapters that have been completely revised with the addition of the latest concepts, devices, applications, literature, and two new chapters, provides a comprehensive coverage of the fundamentals of liquid crystal physical, optical, electro- and nonlinear optical properties, and related optical phenomena. It is intended for students in their final years of undergraduate studies in the sciences and beginning graduate students and researchers. It will also serve as a general useful introductory guide to all newcomers to the field of liquid crystals and contemporary optics and photonics materials and devices.
Studies of liquid crystals are highly inter- and multidisciplinary, encompassing physics, materials science, optics, and engineering. Liquid crystal science and technologies are rapidly advancing. As such, details of actual devices and applications may likely change or become obsolete. In order to present a treatment that is useful and more readily understandable to the intended readers, I have limited the discussion to only the fundamentals that can withstand the passage of time. Wherever possible and without loss of the physics, I have replaced vigorous theoretical formalisms with their simplified versions, for the sake of clarity.
Chapters 1–5 cover the basic physics and optical properties of liquid crystals intended for beginning workers in liquid crystal related areas. Although the major focus is on nematics, we have included sufficient discussions on other mesophases of liquid crystals such as the smectics, ferroelectrics, and cholesterics to enable the readers to proceed to more advanced or specialized topics elsewhere. New sections have also been added. For example, in Chapter 4, a particularly important addition is a quantitative discussion of the optical properties and fundamentals of one-dimensional photonic crystal band structures. Dispersion is added to fill in an important gap in most treatments of cholesteric liquid crystals.
In Chapter 6, we explore the fundamentals of liquid crystals for electro-optics and display, and nondisplay related applications such as sensing, switching and specialized nanostructured tunable photonic crystals and frequency selective surfaces. In Chapter 7 we provide a thorough account of the various theoretical and computational techniques used to describe optical propagation through liquid crystals and anisotropic materials.
Chapters 8–12 provide the most comprehensive self-contained treatment of nonlinear optics of liquid crystals available anywhere, and have greatly expanded on the coverage of the same subject matter in the previous edition of the book with updated literature reviews and fundamental discussions. In particular, readers will find quantitative and complete theories and analysis of important nonlinear optical processes such as photorefractivity, various all-optical image/beam processing, stimulated scattering and optical phase conjugation, nonlinear multiphoton absorptions, and optical limiting of short laser pulses and continuous-wave lasers.
During the course of writing this book, as in my other work, I have enjoyed valuable encouragement and support from a wide spectrum of people. First and foremost is my wife, Chor San. Her patience, understanding, and unqualified support are important sources of strength and motivation. I would also like to express my gratitude to my present and former students and co-authors for valuable contributions to the advances we have made together and the rewarding life experiences. Support from the National Science Foundation, Army Research Office, Air Force Office of Scientific Research, Defense Advanced Research Projects Agency, and Naval Air Development Center over the years is also gratefully acknowledged.
IAM-CHOON KHOO
University Park, Pennsylvania
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