Download or read book Optical Trapping of Nematic and Chiral Nematic Liquid Crystalline Droplets written by Yiming Yang and published by . This book was released on 2009 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Liquid Crystal Colloids written by Igor Muševič and published by Springer. This book was released on 2017-05-14 with total page 313 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book brings together the many concepts and discoveries in liquid crystal colloids contributed over the last twenty years and scattered across numerous articles and book chapters. It provides both a historical overview of the development of the field and a clear perspective on the future applications in photonics. The book covers all phenomena observed in liquid crystal colloids with an emphasis on experimental tools and applications of topology in condensed matter, as well as practical micro-photonics applications. It includes a number of spectacular manifestations of new topological phenomena not found or difficult to observe in other systems. Starting from the early works on nematic colloids, it explains the basics of topological defects in ordered media, charge and winding, and the elastic forces between colloidal particles in nematics. Following a detailed description of experimental methods, such as optical tweezing and particle tracking, the book eases the reader into the theoretical part, which deals with elastic deformation of nematic liquid crystals due to inclusions and surface alignment. This is discussed in the context of basic mean field Landau-de Gennes Q-tensor theory, with a brief explanation of the free-energy minimization numerical methods. There then follows an excursion into the topology of complex nematic colloidal structures, colloidal entanglement, knotting and linking. Nematic droplets, shells, handlebodies and chiral topological structures are addressed in separate chapters. The book concludes with an extensive chapter on the photonic properties of nematic dispersions, presenting the concept of integrated soft matter photonics and discussing the concepts of nematic and chiral nematic microlasers, surface-sensitive photonic devices and smectic microfibers. The text is complemented by a large bibliography, explanatory sketches and beautiful micrographs.

Download or read book Topological Formations in Chiral Nematic Droplets written by Gregor Posnjak and published by Springer. This book was released on 2018-09-06 with total page 186 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this book Gregor Posnjak unravels the long-standing mystery of the internal director structure of chiral nematic droplets, which has been studied both experimentally and theoretically since the 1970s. To do so, he develops a new method for the reconstruction of director fields from a set of fluorescent confocal polarising microscopy images, which he augments with a simulated annealing algorithm. This allows the full reconstruction of 3D director fields, describing the ordering of the liquid crystal. The reconstruction procedure and its principles, which are applicable to other methods of studying vector fields, are explained in detail. The method is subsequently used to explore complex 3D structures in chiral nematic liquid crystal droplets with perpendicular surface anchoring. Twentyfour distinct states are identified and presented, including the layered structures of different symmetries and states with multiple topological point defects, separated by localized chiral structures. In closing, the book reports on the first observation of topological point defects with higher topological charges q = −2 and q = −3.

Download or read book Optical Activity and Turbidity in Chiral Nematic Liquid Crystals written by Yuxi Yang and published by . This book was released on 1999 with total page 114 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Liquid Crystals With Nano And Microparticles In 2 Volumes written by Jan P F Lagerwall and published by World Scientific. This book was released on 2016-10-10 with total page 944 pages. Available in PDF, EPUB and Kindle. Book excerpt: 'The overall book content is excellently coordinated to form a synchronised story, interesting to a broad scientific audience … The book summarises the present knowledge in the field, introduces fundamental concepts to the beginners, describes key measuring methods and presents several different typical demonstrative systems, some of them exhibiting an extraordinary rich spectrum of structures and superstructures. I am sure that with time the book will become an attractor to a broad audience (physicists, chemists, material scientists, engineers, etc.), ranging from students, beginners in the field to experienced researchers. To summarise, this is the book that I have been missing on my bookshelf.'Liquid Crystals TodayWhile liquid crystals are today widely known for their successful application in flat panel displays (LCDs), academic liquid crystal research is more and more targeting situations where these anisotropic fluids are put to completely different use, in varying contexts. A particularly strong focus is on colloidal liquid crystals, where particles, bubbles or drops are dispersed in a liquid crystal phase. The liquid crystal can act as a host phase, with the inclusions constituting foreign guests that disturb the local order in interesting ways, often resulting in large-scale positional arrangement and/or uniform alignment of the guests. But it may also be formed by solid particles themselves, if these are of nanoscale dimensions and of disc- or rod-shape, and if they are suspended in an isotropic liquid host at sufficient concentration.This book aims to cover both the modern research tracks, gathering pioneering researchers of the different subfields to give a concise overview of the basis as well as the prospects of their respective specialties. The scope spans from curiosity-driven fundamental scientific research to applied sciences. Over the course of the next decade, the former is likely to generate new tracks of the latter type, considering the exploratory and productive phase of this young research field.

Download or read book Optical Activity and Dynamic Light Scattering in Chiral Nematic Liquid Crystals written by Carlos Heston Ricardo Hunte and published by . This book was released on 2003 with total page 442 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Optics and Nonlinear Optics of Liquid Crystals written by Iam-Choon Khoo and published by World Scientific. This book was released on 1993 with total page 442 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is a monograph/text devoted to a detailed treatment of the optical, electro-optical and nonlinear optical properties of all the mesophases of liquid crystals and related processes, phenomena and application principles. Quantitative data on material and optical parameters spanning the ultraviolet, visible, infrared as well as the microwave regimes are presented along with detailed theoretical treatments of basic liquid crystal physics, material properties and nonlinear optics.Starting with a discussion on the basic building blocks of liquid crystalline molecules, the authors proceed to present in a pedagogical manner current theories, experiments, and applications of these unique and important optical properties of liquid crystals. Numerous tables of hard-to-find liquid crystalline parameters, a self-contained chapter on general nonlinear optics, and comprehensive literature review are also included.

Download or read book Linear and non linear optical properties of highly twisted chiral nematic liquid crystals written by Jonathan Raffe Willmott and published by . This book was released on 2003 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Orientational Optical Nonlinearity of Liquid Crystals written by N. V. Tabiryan and published by CRC Press. This book was released on 1986 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Nematic Liquid Crystal Sessile Droplets In Electric And Magnetic Fields written by Zoltán Karaszi and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nematic Liquid Crystal Sessile Droplets in Electric and Magnetic Fields Abstract of Dissertation Zoltán Karaszi Materials Science Graduate Program, Kent State University Sessile droplets with uniform director structure could be used as tunable optical lenses where the focal length could be controlled by light polarization, viewing angle, and magnetic or electric fields. To achieve that, one must understand the liquid crystal director structure in various external fields. In this dissertation, I presented detailed experimental studies. I summarized the theoretical description of the director structure of uniaxial nematic liquid crystals, such as the formation and dynamics of Néel wall type metastable inversion walls, either in magnetic or electric fields or magnetic and electric fields combined. Sessile nematic droplets allow for studying the combined effect of anchoring at solid and gas interfaces. The combination of various alignments at the two surfaces and external fields results in various director distribution schemes, ranging from a defect-free, almost homogeneous state to configurations with point-, line- and wall defects. We designed a polarizing optical microscope made of non-magnetic materials that could be placed between an electromagnet's poles. The design allowed us to study the effect of various combinations of electric and magnetic fields on nematic liquid crystal sessile droplets. Additionally, a long-range microscope was used to observe the side view of the LC drop. We also built another experimental setup that enabled us to measure the focal length in response to electric fields while rotating the sample between crossed polarizers. (1) Our main experimental findings can be summarized as follows. We showed that under low magnetic fields applied along the base plane of a sessile droplet with homeotropic alignment, the director structure becomes distorted and gradually leads to a defect wall that moves toward the periphery. We explained the director field's magnetic field dependence and the defect walls' formation and motion. We have shown that at a strong enough lateral magnetic field or even at a small field that makes more than 3° with respect to the base plane, the director can be uniformly aligned along the field without the presence of the defect wall. [1] (2) Replacing the magnetic field, an AC electric field was applied along the base plane of a nematic sessile droplet with positive dielectric anisotropy; we also found a rotation of the director toward the electric field and the formation of an inversion wall perpendicular to the applied field. While at low frequencies, the direction of the wall was stationary, just as observed in magnetic fields, above the Maxwell-Wagner frequency, it turned toward the external electric field. In both cases, the defect wall was also swept toward the periphery of the drop, where it eventually disappeared. The defect wall's rotation at high frequencies resulted from the antiparallel orientation of the effective moment vector and the electric field due to the lower dielectric constant and higher electric conductivity of the defect wall than of the rest of the liquid crystal droplet. An exponential time dependence could describe the time dependence of the displacement of the electric field-induced defect wall without any fitting parameter. That, combined with the threshold for director deformation, enabled us to determine both the bend elastic constant and the rotational viscosity using much less substance than existing techniques. Uniform electric field-induced generation, rotation, and linear movement of defect walls is a unique phenomenon in soft matters.[2] (3) Multidimensional solitons and their electric field-induced movement have recently been reported in achiral and chiral nematic liquid crystals. In the presence of competing magnetic AC electric fields on a sessile droplet with positive dielectric anisotropy, we found that the inversion wall induced by a horizontal magnetic field suffers buckling at sufficiently high electric voltage applied vertically. We characterized the time and field dependence of the buckled walls' shape and motion and proposed a physical mechanism to account for the behavior. We note that, due to their spontaneous propagation, the inversion wall can also be considered as a one-dimensional soliton, i.e., a spatially localized shape preserving traveling wave packet such as observed first by J.S. Russell in 1834 in the form of a one-dimensional water wave traveling along a canal near Edinburgh. [3] (4) We also studied the behavior of nematic liquid crystal sessile droplets with negative dielectric anisotropy. We observed several new director configurations depending on the specific combination of the magnetic and electric fields. For example, at high enough voltages applied across the droplet, the radial symmetry breaks, and a spiraling deformation of the Maltese cross appears near the central defect line. This can be attributed to the twist deformation in the vicinity of the central defect line that replaces the more costly bend deformation. Applying a magnetic field perpendicular to the vertical electric field, a twisted inversion wall formed together with a vertical central defect line. When the electric field was applied parallel to the base plane of the droplet, a homeotropic central region formed along the electric field. When this field was applied together with a magnetic field in the same direction, the homeotropic central region became perpendicular to the applied field. [4,5] (5) We measured the focal length of nematic sessile droplets with positive dielectric anisotropy as a function of electric fields applied along the base plane of the lenses. It was observed that the focal length decreases during increasing fields as the effective refractive index, which is inversely proportional to the focal length, increases from "no" to "ne". The focal length of NLC droplets could also be tuned by varying the polarization direction of a linear polarizer placed in front of the lenses. At the same time, a constant AC electric field was applied along the base plane. [6] References: [1] P. Salamon, Z. Karaszi, V. Kenderesi, Buka, and A. Jákli, Liquid Crystal Spherical Caps in Magnetic Fields, Phys. Rev. Res. 2, 023261 (2020). [2] Z. Karaszi, P. Salamon, Á. Buka, and A. Jákli, Lens Shape Liquid Crystals in Electric Fields, J. Mol. Liq. 334, 116085 (2021). [3] Z. Karaszi, M. Máthé, P. Salamon, Á. Buka, and A. Jákli, Electric Field Induced Buckling of Inversion Walls in Lens-Shape Liquid Crystal Droplets, J. Mol. Liq. 365, 120177-1-7 (2022). [4] Z. Karaszi, M. Máthé, P. Salamon, Á. Buka, and A. Jákli, Lens-Shaped Nematic Liquid Crystal Droplets with Negative Dielectric Anisotropy in Electric and Magnetic Fields, Liq. Cryst. DOI: 10.1080/02678292.2022.2134594, published online (October 24, 2022). [5] Ágnes Buka, Péter Salamon, Marcell Máthé, Zoltán Karaszi, and Antal Jákli, Liquid Crystals, 2023, Nematic liquid crystals in lens shape geometry. https://doi.org/10.1080/02678292.2023.2168307 [6] Z. Karaszi, K. Perera, and A. Jákli, Tuning the Focal Length of Sessile Nematic Droplets by Electric Fields, under preparation, (2023).

Download or read book Nonlinear Optics of Nematic Liquid Crystals written by Stephen Duane Durbin and published by . This book was released on 1984 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book An Electric Field Investigation of the Optical Activity for Two Chiral Nematic Liquid Crystals from the Same Homologous Series written by Sherika Nikara Robinson and published by . This book was released on 2012 with total page 99 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Mathematical Methods in Liquid Crystal Optics and Lens Design written by Eric Stachura and published by Springer Nature. This book was released on with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Nonlinear Optical Effects in Liquid Crystals written by George K. Wong and published by . This book was released on 1980 with total page 114 pages. Available in PDF, EPUB and Kindle. Book excerpt: D.C.-field induced optical second-harmonic generation in nematic and cholesteric liquid crystals is investigated. In addition, flexo-electric induces second-harmonic generation in nematic MBBA is studied. The experiments involve the detection of optical radiation at second-harmonic frequency when aligned thin film liquid crystals samples are irradiated with laser beam at the fundamental frequency. The laser used in a Q-switched Nd-YAG laser. Sample alignment is achieved either with rubbing technique or by coating glass spacers with 100 A thick of Si2. Experiments on nematic liquid crystals show that the temperature dependence of nematic order parameters can be obtained from the measurement of d.c.-induced second-harmonic generation. It is also demonstrated that flexoelectric effect can give rise to second-harmonic generation in nematic liquid crystal and the birefringence of nematic crystal can be used to achieve phase-matching. In the cholesteric liquid crystal, it is demonstrated that the lattice momentum associated with the one dimensional periodicity of cholesteric structure can be used to achieve phase-matching. Comparison of the measured temperature dependence of nematic order parameters with the predictions of the existing statistical theories of nematic ordering indicates that these theories are not quantitatively reliable. The phase-matchability of liquid crystals shows that these media may be useful as practical optical harmonic generators. (Author).

Download or read book Flowing Matter written by Federico Toschi and published by Springer Nature. This book was released on 2019-09-25 with total page 309 pages. Available in PDF, EPUB and Kindle. Book excerpt: This open access book, published in the Soft and Biological Matter series, presents an introduction to selected research topics in the broad field of flowing matter, including the dynamics of fluids with a complex internal structure -from nematic fluids to soft glasses- as well as active matter and turbulent phenomena. Flowing matter is a subject at the crossroads between physics, mathematics, chemistry, engineering, biology and earth sciences, and relies on a multidisciplinary approach to describe the emergence of the macroscopic behaviours in a system from the coordinated dynamics of its microscopic constituents. Depending on the microscopic interactions, an assembly of molecules or of mesoscopic particles can flow like a simple Newtonian fluid, deform elastically like a solid or behave in a complex manner. When the internal constituents are active, as for biological entities, one generally observes complex large-scale collective motions. Phenomenology is further complicated by the invariable tendency of fluids to display chaos at the large scales or when stirred strongly enough. This volume presents several research topics that address these phenomena encompassing the traditional micro-, meso-, and macro-scales descriptions, and contributes to our understanding of the fundamentals of flowing matter. This book is the legacy of the COST Action MP1305 “Flowing Matter”.

Download or read book Nonlinear Optical Effects in Nematic Liquid Crystals written by Srisuda Puang-ngern and published by . This book was released on 1985 with total page 262 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Defects in Liquid Crystals Computer Simulations Theory and Experiments written by Oleg D. Lavrentovich and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 356 pages. Available in PDF, EPUB and Kindle. Book excerpt: Topological defects are the subject of intensive studies in many different branches of physics ranging from cosmology to liquid crystals and from elementary particles to colloids and biological systems. Liquid crystals are fascinating materials which present a great variety of these mathematical objects and can therefore be considered as an extremely useful laboratory for topological defects. This book is the first attempt to present together complementary approaches to the investigations of topological defects in liquid crystals using theory, experiments and computer simulations.