Liquid Crystals. Iam-Choon Khoo

Liquid Crystals - Iam-Choon Khoo


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Imagery by Iam‐Choon Khoo

      Cover design by Wiley

      Preface

      Important progress and advances have been made in the multidisciplinary study of liquid crystals since the last edition of this book went into print in 2007. This new edition consists of 12 chapters, most of which have been completely revamped with the latest fundamental breakthrough and understanding of optical, electro‐, and nonlinear optical properties of liquid crystals.

      Chapters 15 cover the basic physics and optical properties of liquid crystals. Besides nematics that are widely used in ubiquitous devices, I have included sufficient discussions on other mesophases of liquid crystals such as the smectics, ferroelectrics, cholesterics, and the Blue‐phase to enable the readers to proceed to more advanced or specialized topics elsewhere. Several new sections have been added. For example, in Chapter 1, I have included a detailed account of the fabrication methods for growing massive single‐crystalline chiral 1‐D and 3‐D photonic crystals based on cholesteric and Blue‐phase liquid crystals and the feasibility of using cholesteric liquid crystals for ultrafast modulation of picosecond and femtosecond lasers of complex vector fields.

      In Chapter 6, we explore the fundamentals of liquid crystals for electro‐optics and display and non‐display‐related applications such as sensing, switching, and specialized nanostructured tunable photonic crystals, frequency selective surfaces, and metamaterials. In Chapter 7, we provide a thorough account of theoretical and computational techniques used to describe optical propagation through liquid crystals and anisotropic materials. Chapters 812 provide a comprehensive, self‐contained treatment of nonlinear optics of liquid crystals, from classical as well as quantum mechanical standpoints, 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.

      I have limited most discussions to only the fundamentals and device working principles that can withstand the passage of time. Wherever possible and for the sake of clarity, I have replaced vigorous theoretical formalisms with their simplified versions. Almost all of the results contained in the book are taken from my research projects, which have been supported over the years by grants and contracts from the National Science Foundation, Air Force Office of Scientific Research, Army Research Office, the (Patuxent River) Naval Air Development Center, the Defense Advanced Research Projects Agency and Wright Patterson Research Laboratory. I would like to thank my graduate students for their valuable participation in these projects, and support from colleagues and collaborators from all over the world I have befriended and interacted with in the four decades since I ventured into the wonderful world of liquid crystals.

      Iam‐Choon Khoo

       Carlsbad, California, June 2021

      Liquid crystals are wonderful materials. In addition to the solid crystalline and isotropic liquid phases, they exhibit many so‐called mesophases in which they flow like ordinary liquids yet possess crystalline properties [1]. These mesophases are characterized by many unique physical and optical properties and offer a fertile ground for several areas of fundamental pursuits, as well as applications in display screens of ubiquitous devices, photonics, THz and microwave and biomedical systems [2–8].

      Examples of side chain and terminal groups are alkyl (CnH2n+1), alkoxy (CnH2n+1O), and others such as acyloxyl, alkyl carbonate, alkoxy carbonyl, and the nitro and cyano groups. The Xs of the linkage groups are simple bonds or groups such as stilbene (—

—), ester (—
—), tolane (—
—), azoxy (—
—), Schiff base (—
—), acetylene ( —
—), and diacetylene (—
). The names of liquid crystals are often fashioned after the linkage group (e.g. Schiff‐base liquid crystal). There are quite a number of aromatic rings. These include saturated cyclohexane or unsaturated phenyl, biphenyl, and terphenyl in various combinations.


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