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Myhre, Graham. "Patterned Liquid Crystal Polymer Retarders, Polarizers, and Sources." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/228152.
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Liquid crystals are traditionally aligned via a rubbed substrate. The rubbing creates anisotropic defects and strain in the material which provide an energetically favorable orientation for the liquid crystal (LC). This is a well-developed technology that is used in virtually all liquid crystal displays (LCDs). However, it is only capable of uniform alignment on a large planar substrate. This work utilizes a new class of photoalignment materials (PM) that replace the traditional buffing technique. PMs allow for patterned LC alignment using polarized photo-lithography. Further, instead of using a nematic liquid crystal, a UV curable liquid crystal polymer (LCP) is coated on this patterned alignment material. This generates a cured, aligned, and patterned thin film that has retardance and diattenuation if a dichroic dye is incorporated in the LCP. Using these materials and methods, retarders, polarizers, and polarized fluorescent sources are fabricated with dimensions as small as a few microns. In addition to exploring the material and processing properties of the PM and LCP system, arrays of micropolarizer are fabricated for the construction of a prototype polarization camera, termed an imaging polarimeter. An imaging polarimeter is a device that measures not only the intensity but also the polarization state of a light field. My imaging polarimeter design incorporates a patterned LCP polarizer focal plane array (FPA) that is aligned and mounted to a charge-couple-device (CCD) image sensor. A polarizer FPA allows an individual pixel on a CCD sensor to detect a unique polarization state, such as a specific linear polarization orientation or right or left handed circular polarization. Neighboring pixels are designed to detect different states and each cluster can then estimate the incident polarization state. Results of a linear LCP polarimeter operating in the visible spectrum are presented.
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Lam, Wai Sze Tiffany. "Anisotropic Ray Trace." Diss., The University of Arizona, 2015. http://hdl.handle.net/10150/556957.
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Optical components made of anisotropic materials, such as crystal polarizers and crystal waveplates, are widely used in many complex optical system, such as display systems, microlithography, biomedical imaging and many other optical systems, and induce more complex aberrations than optical components made of isotropic materials. The goal of this dissertation is to accurately simulate the performance of optical systems with anisotropic materials using polarization ray trace. This work extends the polarization ray tracing calculus to incorporate ray tracing through anisotropic materials, including uniaxial, biaxial and optically active materials. The 3D polarization ray tracing calculus is an invaluable tool for analyzing polarization properties of an optical system. The 3×3 polarization ray tracing P matrix developed for anisotropic ray trace assists tracking the 3D polarization transformations along a ray path with series of surfaces in an optical system. To better represent the anisotropic light-matter interactions, the definition of the P matrix is generalized to incorporate not only the polarization change at a refraction/reflection interface, but also the induced optical phase accumulation as light propagates through the anisotropic medium. This enables realistic modeling of crystalline polarization elements, such as crystal waveplates and crystal polarizers. The wavefront and polarization aberrations of these anisotropic components are more complex than those of isotropic optical components and can be evaluated from the resultant P matrix for each eigen-wavefront as well as for the overall image. One incident ray refracting or reflecting into an anisotropic medium produces two eigenpolarizations or eigenmodes propagating in different directions. The associated ray parameters of these modes necessary for the anisotropic ray trace are described in Chapter 2. The algorithms to calculate the P matrix from these ray parameters are described in Chapter 3 for anisotropic ray tracing. This P matrix has the following characteristics: (1) Multiple P matrices are calculated to describe the polarization of the multiple eigenmodes at an anisotropic intercept. (2) Each P matrix maps the orthogonal incident basis vectors (Ê_m, Ê_n, Ŝ) before the optical interface into three orthogonal exiting vectors (a_m Ê'_m, a_n Ê'_n, Ŝ') after the interface, where a_m and a_n are the complex amplitude coefficients induced at the intercept. The ray tracing algorithms described in this dissertation handle three types of uncoated anisotropic interfaces isotropic/anisotropic, anisotropic/isotropic and anisotropic/anisotropic interfaces. (3) The cumulative P matrix associated with multiple surface interactions is calculated by multiplying individual P matrices in the order along the ray path. Many optical components utilize anisotropic materials to induce desired retardance. This important mechanism is modeled as the optical phase associated with propagation. (4) The optical path length OPL of an eigenpolarization along an anisotropic ray path is incorporated into the calculation of each P matrix. Chapter 4 presents the data reduction of the P matrix of a crystal waveplate. The diattenuation is embedded in the singular values of P. The retardance is divided into two parts: (A) The physical retardance induced by OPLs and surface interactions, and (B) the geometrical transformation induced by geometry of a ray path, which is calculated by the geometrical transform Q matrix. The Q matrix of an anisotropic intercept is derived from the generalization of s- and p-bases at the anisotropic intercept; the p basis is not confined to the plane of incidence due to the anisotropic refraction or reflection. Chapter 5 shows how the multiple P matrices associated with the eigenmodes resulting from propagation through multiple anisotropic surfaces can be combined into one P matrix when the multiple modes interfere in their overlapping regions. The resultant P matrix contains diattenuation induced at each surface interaction as well as the retardance due to ray propagation and total internal reflections. The polarization aberrations of crystal waveplates and crystal polarizers are studied in Chapter 6 and Chapter 7. A wavefront simulated by a grid of rays is traced through the anisotropic system and the resultant grid of rays is analyzed. The analysis is complicated by the ray doubling effects and the partially overlapping eigen-wavefronts propagating in various directions. The wavefront and polarization aberrations of each eigenmode can be evaluated from the electric field distributions. The overall polarization at the plane of interest or the image quality at the image plane are affected by each of these eigen-wavefronts. Isotropic materials become anisotropic due to stress, strain, or applied electric or magnetic fields. In Chapter 8, the P matrix for anisotropic materials is extended to ray tracing in stress birefringent materials which are treated as spatially varying anisotropic materials. Such simulations can predict the spatial retardance variation throughout the stressed optical component and its effects on the point spread function and modulation transfer function for different incident polarizations. The anisotropic extension of the P matrix also applies to other anisotropic optical components, such as anisotropic diffractive optical elements and anisotropic thin films. It systematically keeps track of polarization transformation in 3D global Cartesian coordinates of a ray propagating through series of anisotropic and isotropic optical components with arbitrary orientations. The polarization ray tracing calculus with this generalized P matrix provides a powerful tool for optical ray trace and allows comprehensive analysis of complex optical system.
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Hong, Qi. "WIDE VIEWING ANGLE LIQUID CRYSTAL DISPLAYS." Doctoral diss., University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4042.
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In this dissertation, novel phase compensation technologies are applied to the designs of wide viewing angle and high transmittance liquid crystal displays. First, a design of wide viewing angle liquid crystal displays utilizing crossed linear polarizers is proposed. The designed multi-domain vertical-alignment liquid crystal display predicts superb contrast ratio over wide viewing angles. Next, to increase the bright state transmittance while maintain the high contrast. Finally, to reduce the cost and improve the applicability of the broadband and wide-view circular polarizer, the device configuration of the broadband and wide-view circular polarizer is significantly simplified by the application of biaxial compensation films. The produced states of polarization remain close to the ideal circular polarization over a wide range of incident angles within the visual spectrum. With this circular polarizer, the presented wide-view liquid crystal display predicts high contrast ratio as well as high and uniform transmittance over wide viewing angles within the visual spectrum. ratio, wide viewing angle circular polarizers are developed. The produced states of polarization are very close to the ideal circular state of polarization over a wide range of incident angles within the visual spectrum. This guarantees not only high contrast ratio but also high and uniform transmittance.<br>Ph.D.<br>School of Electrical Engineering and Computer Science<br>Engineering and Computer Science<br>Electrical Engineering
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Sui, Yongqiang. "Anisotropic organic materials ferroelectric crystals and spin-polarized radicals /." Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/5933.
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Thesis (Ph. D.)--University of Missouri-Columbia, 2007.<br>The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed Mar. 13, 2009). Includes bibliographical references.
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Taborelli, Mauro. "Magnetism of epitaxial thin films and single-crystal surfaces studied with spin-polarized secondary electrons /." [S.l.] : [s.n.], 1988. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=8545.
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Arumugam, Anitha. "Development of method for measurement of passive losses in Cr²⁺:ZnSe and Cr²⁺:ZnS laser crystals using polarized laser beam." Birmingham, Ala. : University of Alabama at Birmingham, 2008. https://www.mhsl.uab.edu/dt/2008m/arumugam.pdf.
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Burt, Jason Bryan. "A study of the crystal chemistry, electron density distributions, and hydrogen incorporation in the Al₂SiO₅ polymorphs." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/27756.
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The Al₂SiO₅ polymorphs have been examined to provide new insights into their chemical bonding, their crystal chemistry, their equations of state, and the incorporation of water in the form of hydroxyl in their structures. The Al₂SiO₅ polymorphs provide a unique structural assemblage for a crystal chemical examination due to the variation in Al coordination in the structures where Al is in 4-fold, 5-fold, and 6-fold in sillimanite, andalusite, and kyanite, respectively. Consequently, the Al₂SiO₅ polymorphs have been examined with a combination of experimental (high pressure X-ray diffraction and Polarized FTIR spectroscopy) and theoretical (VASP and Crystal 98) methods.
An experimental high pressure X-ray diffraction study on andalusite and sillimanite has constrained their equation of state and the pressure derivatives of their bulk modulus with pressure. Additionally, the effect of pressure on the crystal structures has been examined, where the main structural response is compression of the AlO₆ octahedra. Comparatively, compression of the AlO₆ octahedra in andalusite is more anisotropic, while the major direction of axial compressibility in both structures is dependent on the orientation of the AlO6 octahedra.
In order to better understand the crystal chemistry of the Al-O and Si-O bonds in the polymorphs, ELF isosurfaces were examined. ELF isosurfaces represent a graphical representation of the localized electron probability density. Six distinct types of ELF isosurfaces were observed in the Al₂SiO₅ polymorphs resulting from differences in the geometry, coordination, and coordinated cation atomic number surrounding the oxygens within the crystal structures. The ELF was also shown to be isostructurally related to electron density difference maps.
In a combined experimental and theoretical investigation of the Al₂SiO₅ polymorphs, potential protonation sites within the crystal structures were determined at an atomic level with polarized FTIR spectroscopy and analysis of (3,-3) critical points of the negative Laplacian. The polarized FTIR spectra indicate the orientation of the OH dipole in the three polymorphs and the (3,-3) critical points indicate regions of locally concentrated electron density. Potential protonation sites were determined based on the value of the negative Laplacian, the underbonded nature of the oxygens, and the number of surrounding cations.<br>Ph. D.
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Valenzuela, Espinel Yovanny Alexander 1981. "Estudo das características ópticas de fibras de cristal fotônico (PCF) sob pressão hidrostática aplicada." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/277574.
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Orientadores: Cristiano Monteiro de Barros Codeiro, Marcos Antonio Ruggieri Franco<br>Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin<br>Made available in DSpace on 2018-08-20T13:14:05Z (GMT). No. of bitstreams: 1
ValenzuelaEspinel_YovannyAlexander_M.pdf: 51370027 bytes, checksum: 2f925ea5d4b6a8642e1244ad21e8e82b (MD5)
Previous issue date: 2011<br>Resumo: Foram realizados estudos sobre o controle de propriedades ópticas, por meio de pressão, e sensibilidade à pressão com fibras de cristal fotônico (PCF). No primeiro caso foi demonstrado por meio de simulações, uma nova forma para obter e sintonizar com pressão hidrostática externa o estado monomodo e única polarização em fibras PCF de polimetilmetacritalo (PMMA). Em relação à sensibilidade à pressão hidrostática, o comportamento espectral do coeficiente de sensibilidade de varias fibras PCF em sílica, Cs = (?? / ?P) (onde ?? é a variação num mínimo do espectro de transmissão de uma fibra PCF que acontece quando a pressão hidrostática externa muda em LlP), é calculado teoricamente e corroborado experimentalmente. Com a finalidade de estudar teoricamente o coeficiente Cs, a birrefringência de grupo e a sensibilidade da birrefringência modal de fase à pressão são simuladas para as fibras. Expressões analíticas do coeficiente Cs na aproximação de primeira e segunda ordem são calculadas. Nas duas aproximações é confirmado um aumento do Cs para comprimentos de onda no visível devido à birrefringência de grupo. Para baixas pressões, tal comportamento é corroborado experimentalmente. Segundo a literatura apresentada até agora a possibilidade de otimizar o coeficiente Cs, fazendo uso da birrefringência de grupo no visível e ao mesmo tempo incorporando geometrias com uma alta anisotropia geométrica para aumentar a sensibilidade da birrefringência modal de fase à pressão, não tem sido explorada. Na aproximação de segunda ordem do coeficiente Cs são incorporadas as mudanças do comprimento de onda e da pressão e são comparadas com a aproximação de primeira ordem. Cálculos analíticos foram feitos e apresentados nos Apêndices B e C. As equações do efeito fotoelástico, determinantes para realizar as simulações com o software (COMSOL 3.5a), são apresentadas no Apêndice B, relações que descrevem o coeficiente Cs de fibras PCF são apresentadas no (Apêndice C)<br>Abstract: Abstract Studies about both the active control of optical properties by means of external hydrostatic pressure and pressure sensitivity in photonic crystal fibers (PCFs) were made. In the first case, a new form to obtain and tune, by using pressure, the single-mode single-polarization state in microstructured polymer optical fibers (mPOFs) is demonstrated by simulations. In relation to pressure sensitivity, the spectral behavior of the sensitivity coefficient of some PCFs in silica, Cs = (?? / ?P) (where ?? é is the change in a minimum of the transmission spectrum for a PCF as a consequence of the change in the external hydrostatic pressure 11P that is applied on the fiber), is calculated and corroborated experimentally. In order to investigate the coefficient Cs, the group birefringence and the sensitivity of phase modal birefringence to pressure are calculated in the fibers. Analytical expressions for the coefficient Cs in the first and second order approximation are calculated. In these two approximations an increase of the coefficient Cs is confirmed to wavelengths in the visible. To low pressures this behavior is corroborated experimentally. At the best of our knowledge, the possibility to optimize the coefficient (Cs) by using the group birefringence and geometries with high geometric anisotropy to enhancing the sensitivity of phase modal birefringence to pressure has not been investigated. In the coefficient Cs with the second order approximation are incorporated the changes of the wavelength and pressure and are compared with the first approximation. On the other hand, analytic calculates are realized in the Appendixes B and C. The equations related to the photoelastic effect were calculates (Appendix B). Finally, the relations that describing the behavior of pressure sensitivity also were calculates (Appendix C)<br>Mestrado<br>Física<br>Mestra em Física
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Li, Tian-Yi, You-Xuan Zheng, and Yong-Hui Zhou. "Iridium(III) phosphorescent complexes with dual stereogenic centers: single crystal, electronic circular dichroism evidence and circularly polarized luminescence properties." Royal Society of Chemistry, 2016. https://tud.qucosa.de/id/qucosa%3A36123.
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Iridium complexes with a chiral metal center and chiral carbons, Λ/Δ-(dfppy)₂Ir(chty-R) and Λ/Δ-(dfppy)2Ir(chty-S), were synthesized and characterized. These isomers have the same steadystate photophysical properties, and obvious offsets in ECD spectra highlight both the chiral sources. Each enantiomeric couple shows mirror-image CPL bands with a dissymmetry factor in the order of 10ˉ³.
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Polowsky, Patrick. "Analysis of surface crystals on soft washed rind cheeses using polarized light microscopy and their effect on the sensory perception of grittiness." ScholarWorks @ UVM, 2018. https://scholarworks.uvm.edu/graddis/864.
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With the rising popularity of artisanal cheese in the United States, the soft washed rind category has emerged as a fast-growing segment of the marketplace. There is much anecdotal evidence to suggest a common sensorial defect in soft washed rind cheese is a gritty/sandy texture attributed to crystal growth on the rind of these cheeses
A preliminary study was undertaken to develop a set of criteria to visually identify crystals found on soft washed rind cheeses. Single crystal identities were presumptively determined using polarized light microscopy (PLM), and cross-checked using powder x-ray diffractometry (PXRD). Two distinct crystal groupings were determined based on these metrics. Group 1 crystals had high birefringent coloring, angle of extinction (AE) ≈ 90°, and were smaller and less circular than Group 2 crystals (P<0.05). Group 2 crystals had no birefringent coloring and AE ≈ 18°. Using established mineralogical data, Group 1 and Group 2 crystals were identified to be struvite and ikaite, respectively. These crystalline bodies are situated in an amorphous cheese matrix (i.e. smear), which create difficulties when examining via PLM and PXRD, leading to high background noise. To remedy these issues, a novel method for harvesting crystals was developed. Smear scrapings were immersed in NaOH (pH=10) to dissolve smear material, which resulted in improved PLM and PXRD performance.
A subsequent observational study was conducted to understand the prevalence of surface crystals and grittiness associated with washed rind cheeses sourced from the U.S.A. and Europe. Crystal types were identified via PXRD and PLM. Crystal size and shape (circularity) metrics were determined via PLM and image analysis. A descriptive sensory panel (n=12) was used to evaluate grittiness presence and intensity. Identified crystal types included ikaite, struvite, calcite, and brushite. Mean crystal length and area ranged from ~30μm to ~1100μm, and ~500μm2 to ~200,000μm2, respectively. Sensory perception threshold for grittiness occurred at a mean crystal length of ~70μm and mean crystal area of ~2900μm2. Below these threshold levels, cheeses presented with negligible grittiness. Above these threshold levels, grittiness was highly correlated with crystal length and area (r=0.93 and 0.96, respectively; P<0.001). These results indicate surface crystals have a direct impact on the sensorial quality of soft washed rind cheeses.
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Georgiev, Georgi Yordanov. "Structural studies of polymers and polymer liquid crystals by X-ray scattering, thermal analysis and ellipsometric studies through polarized light microscopy /." Thesis, Connect to Dissertations & Theses @ Tufts University, 2002.
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Thesis (Ph.D.)--Tufts University, 2002.<br>Adviser: Peggy Cebe. Submitted to the Dept. of Physics. Includes bibliographical references. Access restricted to members of the Tufts University community. Also available via the World Wide Web;
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Sánchez, Castillo Alberto [Verfasser]. "Polarized micro-Raman spectroscopy: A modern technique to study the molecular orientational order of nematic and smectic liquid crystals / Alberto Sánchez Castillo." München : Verlag Dr. Hut, 2013. http://d-nb.info/1042306931/34.
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Park, Min Sang. "Application of polarized Raman spectroscopy for analysis of phase transitions and anisotropic behavior of soft condensed matter." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/47539.
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The importance of soft matter research, as a major class of materials including liquid crystals, polymers, colloids, emulsions, and forms, is attributed to the behavior resemblances in each branch of soft matter responding to the external perturbations. Hence, one of the most required inquiries in soft matter physics is understanding how the structures with characteristic length scales evolve in response to external perturbations, and concomitant phase transitions. We have focused on adopting polarized Raman spectroscopy to probe phase transitions in soft materials consisting of anisometric components and the evolution of molecular orientational ordering as a complementary tool to other methodologies, but distinct in some respects. The primary task is quantifying the degree of molecular orientation, i.e., obtaining orientational order parameters, in liquid crystal (LCs) system. Thermal evolution of orientation degree in a hitherto elusive biaxial nematic (Nb) phase as well as a commonly known uniaxial nematic (Nu) phase were interrogated from the measurements of anisotropy in polarized Raman intensities. We demonstrated reliable and applicable method to quantify the orientation degree for systems possessing anisotropic ordering.
We also addressed a strong potential of Raman spectroscopy that the changes of vibrational energy reflect the variations of intermolecular interactions and structural changes on the molecular level induced by phase transitions. As a subfield of soft matter, we characterized phase transitions and anisotropic ordering observed in an evaporating conjugated polymer solution and elucidated the mechanism of the entities undergoing phase transitions using mainly polarized Raman spectroscopy. In addition, we have shown that tracking Raman spectral changes can provide valuable information for understanding structure-property relations when the measurements of the evolution in physical properties are carried out simultaneously.
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Bayuadri, Cosmas. "Stability of sodium sulfate dicarbonate (~2Na₂CO₃• Na₂SO₄) crystals." Thesis, Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/11507.
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Research on salts species formed by evaporation of aqueous solution of Na2 in the early 1930s. The thermodynamic, crystallographic and many other physical and chemical properties of most of the species formed from this solution has been known for decades. However, there was no complete information or reliable data to confirm the existence of a unique double salt that is rich in sodium carbonate, up until five years ago when a research identified the double salt (~2Na ₂ CO ₃ • Na ₂ SO ₄) from the ternary system Na₂CO ₃Na₂SO ₄ H₂O. Crystallization of this double salt so called sodium sulfate dicarbonate (~2Na ₂ CO ₃ • Na ₂ SO ₄) is known to be a primary contributor to fouling heat transfer equipment in spent-liquor concentrators used in the pulp and paper industry. Therefore, understanding the conditions leading to formation of this double salt is crucial to the elimination or reduction of an industrial scaling problem. In this work, double salts were generated in a batch crystallizer at close to industrial process conditions. X-ray diffraction, calorimetry, and microscopic observation were used to investigate the stability of the salts to in-process aging, isolation and storage, and exposure to high temperature. The results show that care must be taken during sampling on evaporative crystallization. Two apparent crystal habits were detected in the formation of sodium sulfate dicarbonate; the favored habit may be determined by calcium ion impurities in the system. The results also verify that sodium sulfate dicarbonate exists as a unique phase in this system and that remains stable at process conditions of 115-200℃
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Bita, Ion. "Breaking symmetries in ordered materials : spin polarized light transport in magnetized noncentrosymmetric 1D photonic crystals, and photonic gaps and fabrication of quasiperiodic structured materials from interference lithography." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36205.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006.<br>"February 2006."<br>Includes bibliographical references.<br>Effects of breaking various symmetries on optical properties in ordered materials have been studied. Photonic crystals lacking space-inversion and time-reversal symmetries were shown to display nonreciprocal dispersion relations, and to exhibit a remarkable set of symmetry-related properties. Even in 1D, these materials are found to display indirect photonic band gaps, backward wave propagating modes (antiparallel phase and group velocities) which enable negative refraction at the air-crystal interface, ability to allow bending light with perpendicular magnetic fields, unidirectional superprism effects, etc. By calculating the complex photonic band structure, we show that the gap modes differ fundamentally from the commonly assumed evanescent modes with purely imaginary wave vectors - solely due to symmetry, we show that the gaps of nonreciprocal photonic crystals have complex wave vectors with both imaginary components and non-zero, frequency dependent real components. This basic finding is further studied in the context of tunneling dynamics, by considering the problem of tunneling time for nonreciprocal photonic band gap barriers (the tunneling wave packet has an energy in the middle of the gap).<br>(cont.) It was found that the classical Hartman effect (independence of tunneling time on barrier length, beyond a certain length), previously implied as universal, is forbidden solely due to symmetry. Instead of a classical zero group delay, we find that tunneling wave packets with opposite spins display non-zero group delays, with opposite signs. Due to analogies based on symmetry, these results directly impact the problem of spin-polarized electronic tunneling in magnetized noncentrosymmetric semiconductors, such as GaMnAs or carbon nanotubes with applied axial magnetic fields. An interference lithography based fabrication process was developed to produce 2D and 3D quasiperiodically structured materials, which have long-range order but break translational symmetry. Multiple exposure interference lithography was used to fabricate 2D quasicrystals with feature sizes as small as 100nm. Replica molding was used to fabricate transparent and conformable 2D quasiperiodic phase masks, which subsequently allowed the fabrication of 3D structured materials with quasiperiodicity by coherent diffraction lithography. The effect of the higher point group symmetries of 2D quasicrystals on photonic band gap formation (TM polarized only) was studied by finite difference time domain calculations, and it was found that increasing the rotational symmetry does not always lead to wider gaps.<br>by Ion Bita.<br>Ph.D.
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Hoffmann, Michael. "Frenkel and Charge-Transfer Excitons in Quasi-One-Dimensional Molecular Crystals with Strong Intermolecular Orbital Overlap." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2000. http://nbn-resolving.de/urn:nbn:de:swb:14-994680323218-86403.
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We present a theoretical and experimental study on the lowest electronically excited states in quasi-one-dimensional molecular crystals. The specific calculations and the experiments are performed for the model compounds MePTCDI (N-N'-dimethylperylene-3,4:9,10-dicarboximide) and TCDA(3,4:9,10-perylenetetracarboxylic dianhydride). The intermolecular interactions between nearest neighbors are quantum chemically analyzed on the basis of semi-empirical (ZINDO/S) Hartree-Fock calculations and a singly excited configuration interaction scheme. Supermolecular dimer states are projected onto a basis set of localized excitations. The nature of the lowest states is then completely explained as a superposition of molecular and low lying charge-transfer excitations. The CT excitations show a significant intrinsic transition dipole, which is oriented approximately parallel to the molecular planes and has a large component along the molecular M-axis. The exciton states in the one-dimensional stacks are described by a model Hamiltonian that includes interactions between three vibronic levels of the lowest molecular excitation and nearest-neighbor CT excitations. The three-dimensional crystal structure is considered by Frenkel exciton transfer between arbitrary molecules. This model is compared to polarized absorption spectra. With a small set of parameters, we can describe the key features of the absorption spectra, the polarization behavior, and the Davydov splitting. The variation of the polarization ratio for the various exciton states is analyzed as a direct qualitative proof for the mixing between Frenkel and charge-transfer excitons.
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Dumont, George Pierre Jr. "The use of carbonation and fractional evaporative crystallization in the pretreatment of Hanford nuclear wastes." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/24716.
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Thesis (M. S.)--Chemical Engineering, Georgia Institute of Technology, 2007.<br>Committee Chair: Dr. Ronald W. Rousseau; Committee Member: Dr. Amyn S, Teja; Committee Member: Dr. Wm. James Frederick Jr.
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Mivelle, Mathieu. "Etude et développement de nano-antennes fibrées pour la microscopie en champ proche optique et la nano-photonique." Phd thesis, Université de Franche-Comté, 2011. http://tel.archives-ouvertes.fr/tel-01062557.
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Dans la première partie de cette thèse, nous tirons parti du concept de nano-antenne optique afind'apporter une solution innovante au problème d'interprétation de la microscopie champ procheoptique (SNOM). En effet, il est connu que certaines nano-antennes développent des réponsesoptiques dipolaires. Dans cette thèse nous démontrons comment l'utilisation d'une nano-ouverturepapillon (nano-antenne dipolaire), à l'extrémité d'une pointe SNOM, permet de détecter et collecteruniquement une seule composante du champ proche électrique. Ce résultat est démontré d'unpoint de vue théorique par l'utilisation de simulation FDTD (Finite Difference Time Domain) et d'unpoint de vue expérimental par la caractérisation, par cette pointe innovante, d'échantillonsdiélectriques (réseaux, cristaux photoniques) et métalliques (milieux désordonnés plasmoniques).Dans une deuxième partie, nous démontrons comment la sonde développée dans la premièrepartie, peut être utilisée comme détecteur du signal émis par un nano-émetteurs (NE) unique. Il estétudié dans cette partie l'effet de couplage entre ces deux objets. Dans un premier temps, après ladescription complète des grandeurs caractéristiques d'un NE, nous démontrons théoriquementl'effet de la pointe sur la réduction du temps de vie de l'état excité et l'augmentation de lafluorescence d'un NE, en régime saturé et non saturé. Puis dans un deuxième temps nousdémontrons expérimentalement comment cette sonde réduit le temps de vie de l'état excité deboites quantiques placées à son extrémité, en comparaison de pointes SNOM plus conventionnellestelle que la pointe diélectrique et la pointe à ouverture circulaire.
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Relaix, Sabrina. "Cristaux liquides cholestériques en conditions non usuelles de photogélification : modulation du profil de réflexion de la lumière." Phd thesis, Université Paul Sabatier - Toulouse III, 2007. http://tel.archives-ouvertes.fr/tel-00179999.
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De part sa structuration en hélice, un Cristal Liquide Cholestérique (CLC) possède des propriétés optiques singulières. La lumière incidente sur un CLC est réfléchie sélectivement, avec une longueur d'onde λ0 associée proportionnelle au pas hélicoïdal et ceci sur une largeur spectrale de quelques dizaines de nm autour de λ0. La quantité de lumière réfléchie est par ailleurs limitée à 50% de la lumière ambiante (non polarisée). <br /><br />Les travaux de thèse se sont focalisés sur l'obtention de propriétés de réflexion de cholestériques gélifiés atypiques, avec deux objectifs de recherche: l'élargissement de la bande de réflexion et l'accroissement de la quantité de lumière réfléchie. <br /><br />La première partie du manuscrit de thèse propose un procédé d'élaboration permettant un élargissement de la bande de réflexion de gels de CLC. Cet objectif est atteint par l'utilisation d'un CLC absorbant la lumière UV, à l'origine d'un gradient d'intensité lors de la gélification. Des études par microscopie optique, spectrophotométrie et microscopie électronique en transmission ont permis de déterminer la distribution structurale à l'origine de la distribution des longueurs d'onde de réflexion observée.<br /><br />La seconde partie du manuscrit se focalise sur l'augmentation de la quantité de lumière réfléchie par un gel réalisé à partir d'un mélange cholestérique qui voit son sens d'hélicité changer avec la température. L'impact de l'histoire de la polymérisation et du parcours en température après gélification sur les propriétés du profil de réflexion sera analysé avec une attention particulière sur la nature et la quantité de la polarisation du faisceau réfléchi.
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Pontillon, Yves. "Étude de la densité de spin de composés magnétiques moléculaires par diffraction de neutrons polarisés." Université Joseph Fourier (Grenoble ; 1971-2015), 1997. http://www.theses.fr/1997GRE10220.
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Au cours de ce travail, nous avons applique la technique de la diffraction de neutrons polarises a l'etude de la densite de spin dans des composes magnetiques moleculaires. Nous avons tout d'abord etudie deux nitronyl nitroxydes presentant une structure en chaine via des liaisons hydrogenes : la densite de spin est majoritairement localisee dans une orbitale antiliante * construite sur les fonctions 2#p des atomes d'azote et d'oxygene des groupes nitroxydes. Par ailleurs, nous avons mis en avant le role primordial des liaisons hydrogenes dans le couplage ferromagnetique intermoleculaire, role confirme par des calculs theoriques ab initio (methode de la fonctionnelle de la densite). Nous nous sommes ensuite interesses a un complexe cuivrique d'une enaminocetone nitroxyde. Nous avons pu determiner qu'une dimerisation quasi totale avait lieu a basse temperature entre deux fonctions nitroxydes, de deux molecules differentes, se faisant face et distantes de 3. 40a. Puis, nous presentons l'etude d'un ferroaimant moleculaire (radical nitronyl nitroxyde). La densite de spin est en grande partie concentree sur le fragment oncno du cycle nit dans une orbitale magnetique moleculaire antiliante *, le couplage ferromagnetique intermoleculaire modifiant l'orientation relative des orbitales magnetiques des deux atomes d'oxygene des fonctions -no, rotation s'accompagnant d'une hybridation sp. La derniere etude presentee dans ce manuscrit a trait a un alkyl nitroxyde presentant un ordre ferromagnetique. Nous avons verifie la localisation majoritaire de l'electron non apparie sur le groupe -no et la nature antiliante * de l'orbitale moleculaire magnetique. Les populations individuelles de spin obtenues sur l'ensemble de la molecule, nous ont permis de proposer un mecanisme expliquant les couplages ferromagnetiques intermoleculaires.
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Seltmann, Jens. "Struktur-Eigenschaftsbeziehungen V-förmiger Mesogene zur Realisierung biaxial nematischer Mesophasen." Doctoral thesis, Universitätsbibliothek Chemnitz, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-67693.
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Die vorliegende Arbeit befasst sich mit der Synthese und der Untersuchung von Struktur-Eigenschaftsbeziehungen neuartiger V-förmiger, formstabiler Mesogene zur Realisierung biaxial nematischer Mesophasen (Nb). Alle synthetisierten Verbindungen besitzen ein formtreues Oligo(phenylenethinylen)-Grundgerüst, an welches laterale Alkyloxyketten und verschiedene terminale Substituenten (z. B. -CN, O(CH2)nCOOEt, Pyridyle) angebunden wurden. Durch dieses spezielle Design erhält man ausschließlich nematische und keine höher geordneten flüssigkristallinen Phasen. Durch den Einsatz verschiedener zentraler heterozyklischer Kernbausteine konnten erfolgreich Öffnungswinkel zwischen 108.9° und 160° realisiert werden. Dabei zeigen Thiadiazolderivate stets enantiotrope Mesophasen, wobei im Hochtemperaturbereich eine uniaxiale Phase mit biaxialen Aggregaten vorliegt. Beim Abkühlen konnte bei etwa 50 °C mittels Polarisationsmikroskopie und dielektrischer Spektroskopie ein Übergang in die Nb-Phase nachgewiesen werden. Die erstmalige Beobachtung eines direkten Übergangs von der isotropen Phase in die Nb-Phase gelang durch den Einsatz von Benzo[1,2-b:4,3-b]dithiophen als Kernbaustein.
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Perny, Sébastien. "Alignement de cristaux liquides par irradiation en lumière linéairement polarisée de film minces de polymères photoréticulables." Cachan, Ecole normale supérieure, 1998. http://www.theses.fr/1998DENS0042.
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L'objectif de ce travail de thèse a été en premier lieu de concevoir et de synthétiser quatre polymères photosensibles utilisables industriellement comme films d'alignement des cristaux liquides. Dans un deuxième temps, des études par spectroscopie UV et IR ont permis de caractériser l'anisotropie et l'évolution de la composition de ces matériaux en cours d'irradiation en lumière linéairement polarisée. Dans le cas général, il a ainsi été possible de mettre en évidence la compétition de deux photo réactions : la cycloaddition 2+2 et l'isomérisation trans/cis. Ainsi, trois espèces cohabitent au sein du film de polymère irradié : les dimères, produits de la cycloaddition de chromophores agrégés ; les isomères cis, issus de l'isomérisation des chromophores isoles ; les chromophores initiaux qui n'ont pas réagi. De plus, nous avons pu constater que l'orientation préférentielle des chromophores inchangés était perpendiculaire a l'axe de polarisation et que, dans certains cas, les dimères étaient préférentiellement formes parallèlement a l'axe de polarisation. Enfin les propriétés d'alignement de ces matériaux ont été étudiés en confinant des cristaux liquides entre deux films de photopolymères irradies. Leur comportement a ensuite été compare a ceux du pvci et du poly(7-methacryloyloxycoumarine) afin de clarifier le mécanisme de photo alignement. Deux mécanismes ont du être envisages. Dans un cas, la sélectivité axiale des réactions photochimiques en lumière polarisée consomme les chromophores préférentiellement orientes le long de l'axe de polarisation. L'anisotropie du film est donc uniquement due à la présence de chromophores inchangés, initialement perpendiculaires à l'axe de polarisation, et le film induit un alignement homogène planaire suivant cet axe. Dans le deuxième cas, l'anisotropie du film est essentiellement due à la formation de dimères le long de l'axe de polarisation, et le film induit un alignement homogène planaire suivant l'axe de polarisation.
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HSU, CHIAO-SEN, and 許喬森. "Feasibility Study on Developing New Circular Polarizers Using Cholesteric Liquid Crystal Device." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/9c7t7v.
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碩士<br>國立高雄師範大學<br>光電與通訊工程學系<br>107<br>In this paper, we mainly study how to develop new circular polarizers using cholesteric liquid crystal device, and apply a specific voltage to the component. Let component`s polarizat¬ion state can switch between unpolarized light and circularly polarized light.
In this experiment, we use the characteristic of right-handed cholesterol liquid crystal which reflect specific wav¬elength and optical rotation.
We superimpose three different pitches cholesteric liquid crystals in a single component to expand the range of the ref¬lection spectrum. Otherwise, we apply a specific voltage to control the switching of its polarization state to achieve the purpose of electrically controlling a large bandwidth circular polarizer.
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吳建利. "Fabrication of Subwavelength Metallic Wire-Grid Polarizers for Liquid Crystal Displays Using Roll-to-Roll Nanoimprint Technology." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/03721929672412033147.
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博士<br>國立清華大學<br>動力機械工程學系<br>101<br>This thesis involves the fabrication of high-performance wire-grid polarizers (WGPs) by using nanoimprint lithography (NIL) for the application of liquid crystal displays (LCDs). To obtain the optimal level of polarization performance in the visible spectrum, the WGPs require an ultra-high-precision and reproducible manufacturing process that can fabricate extremely fine metallic gratings that possess a low density of defects. Most current manufacturers are confronted by a bottleneck, struggling to produce a large volume at a low cost.
Therefore, three nanoimprint platforms were developed using glass and plastic substrates, including batch-type thermal NIL, UVNIL, and roll-to-roll (R2R) UVNIL, and flexible working stamps composed of plastic and nickel alloys to facilitate large-area nanoimprinting that yields products of excellent quality and uniformity. These approaches allowed the optical properties and characteristics of each fabrication process to be thoroughly investigated.
To enhance the fabrication tolerance, repeatability, and optical performance of the WGPs, the grating aspect ratio, profile symmetry, and varying residual layer thicknesses (RLTs) were precisely simulated and controlled to achieve the targeted designs. Applying multilayer WGP grating configurations and optimal metal deposition processing substantially reduced manufacturing difficulties, enabling small WGP pitches to be replaced with large pitches, achieving improved optical performance.
Consequently, 9-nm-linewidth gratings with high aspect ratios larger than 18:1 were fabricated using R2R nanoimprinting and plasma trimming, achieving flexible WGPs that demonstrated high levels of optical performance (up to 12000:1 extinction ratio (ER) with an average transmittance of 83%) and a low color shift (transmittance variation less than 3%).
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Chang, Shu-Wen, and 張書文. "Synthesis of UV-Curable Bistolane Liquid Crystals and Their Applications in Broad-band Cholesteric Polarizer and Polarized Electroluminescence." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/42173915681067980319.
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博士<br>國立交通大學<br>應用化學系<br>90<br>The goal of this study is aimed to synthesize three series of highly conjugated bistolane liquid crystals (LC) with lateral substituents and their corresponding polymers. The corresponding monoacrylate, monooxirane, and diacrylate monomers based on bistolane mesogenes are synthesized. All of the obtained asymmetric monomers reveal an enantiotropic nematic phase. Bistolane liquid crystals with lateral substituents exhibit low melting point and wide nematic range. The synthesized polyacrylates and polyoxiranes containing bistolane side groups exhibit the glass transition temperatures at about 5℃ and the nematic to isotropic temperatures at about 90℃.
In the second part of this study, the reflective cholesteric polarizers based on the bistolane monomers are investigated. The birefringences of the LC monomers are in the range from 0.35 - 0.6 depending on the measuring wavelength. Blending the bistolane LC with the chiral dopant, the corresponding cholesteric LC exhibits a low melting point and high birefringence. The cholesteric LC mixtures were aligned between two glass substrates and cured by UV radiation to form the broad-band cholesteric liquid crystal polarizer.
In the third part of this study, the optical properties of obtained monomers and polymers are investigated. All of the bistolane liquid crystals present UV absorption peaks at about 330 nm, and both solution and film samples show very similar absorption spectra. The PL emissions of bistolane liquid crystals measured in THF and in solid state are at about 380 nm and 430 nm, respectively. The emission maxima of the films are red-shifted compared to the maxima in the solution. These phenomena indicate that the mesogenic groups have the tendency to aggregate in the solid-state and resulted in the decrease of band gap. The EL spectra of bistolane liquid crystals are similar to the PL spectra of bistolane LC. These results indicate that the PL and EL mechanisms of bistolane LCs are similar.
Finally, the polarized EL based on the bistolane monomers was investigated. Polyimide (PI), polyaniline (PA), and poly(3,4-diethylene dioxythiophene) (PEDOT) are used as alignment materials for LCs. The dichroic ratios of the PI-, PA-, and PEDOT-aligned LCs are PI > PA > PEDOT. PI shows the highest alignment ability. The reason could be due to a more linear and rigid main chain structure of PI. The dichroic ratio is defined as the parallel to perpendicular emission intensity. The best dichroic ratios for UV, PL, and EL are 15.2, 13.8, and 7.1, respectively. The order parameter of LC that was coated on PEDOT in the EL device is 0.67.
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Pinto, Marco Gui Alves. "CdTe Matrix Polarimetric Analysis with a Crystal Polarizer." Master's thesis, 2014. http://hdl.handle.net/10316/28871.
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Dissertação de Mestrado em Astrofísica, apresentada à Faculdade de Ciências e Tecnologia da Universidade de Coimbra.<br>A astronomia de raios gamma é um tópico quente na comunidade científica. De
facto, nas últimas décadas o céu de raios gamma evoluiu de um não existente para um
com vários tipos de objetos divididos em ainda mais classes.
O INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) e o FERMI são
as missões atuais que observam os raios gamma do universo em que o primeiro é
sensível para radiação até 10 MeV e o último para energias entre 30 MeV e mais de 300
GeV. Apesar do satélite FERMI ainda ter muitos anos de atividade pela frente, o
INTEGRAL tem um tempo de vida previsto mais curto sem um substituto planeado.
Com isto em mente consórcios internacionais têm tentado desenvolver
instrumentos que ultrapassem o INTEGRAL tanto em sensibilidade como em
performance de polarimetria.
Com a aproximação de uma nova chamada da ESA para uma missão de classe M,
e com a sensibilidade melhorada através do uso de lentes de Laue e da estratificação de
detetores semi-condutores, é urgente que também a capacidade polarimétrica também
seja melhorada. Como os aceleradores de sincrotrão têm uma agenda preenchida, tem
sido desenvolvida uma experiência para fazer medições de polarimetria em laboratório.
Neste primeiro passo procura-se polarizar um feixe de raios gamma de alta energia com
dispersão de Compton num material alvo e depois estudar os parâmetros da polarização
com um detetor pixelizado de telureto de cádmio.
Na primeira fase fizeram-se simulações para otimizar a geometria da experiência.
Estas simulações incluíram o desenvolvimento de software original, para estudar a
polarização de um feixe inicial em vários materiais alvo e o estudo do comportamento
do detetor quando irradiado com um feixe polarizado usando a biblioteca GEANT4
desenvolvida pelo CERN. Enquanto a primeira mostrou que o alumínio é o material mais
indicado para a experiência, a segunda previu um valor de ~0.44 para o factor de
modelação de uma matriz 7x7 e um valor de ~0.36 para uma matriz 3x3.
Com o conhecimento adquirido pelas simulações adaptou-se o sistema e
testaram-se vários parâmetros experimentais de modo a otimizar a experiência e
começar a estudar a performance polarimétrica do detetor. A montagem final permitiu
medir um valor de grau de polarização de 32% que pode ser explicado pela dispersão
nos feixes iniciais e finais assim como pelo ruído presente.
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Lo, Chun-Hsiang, and 羅春祥. "An Electrically Tunable Polarizer Using Dye-doped Liquid Crystal Gels." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/29891624402054075389.
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碩士<br>國立交通大學<br>顯示科技研究所<br>97<br>An electrically tunable polarizer using dye-doped liquid crystal (LC) gels is demonstrated. The main mechanism of such a polarizer is a combination of the light absorption and the scattering owning to dichroic dyes and poly-domains resulting from polymer networks. In this thesis, we observe the morphologies of dye-doped liquid crystal gels by a scanning electron microscopy. The polymer networks perpendicular to the glass substrates are chain-linked by lots of nano-sized polymer grains. The sizes of poly-domains and polymer grains depend on curing temperatures and monomer concentrations. The domain sizes of polymer networks and the sizes of polymer grains increase by increasing the curing temperature. The domain sizes have influence on electro-optical properties of the electrically tunable polarizers. In our experiments, the maximum contrast ratio of the polarizer can be electrically tuned is around 5:1~10:1 at 10�aC curing temperature. The operating voltage is around 30 Vrms. The response time is around ~ 6ms. The optical analysis based on the scattering theory and the absorption theory is discussed as well. Furthermore, we focus on the color issue of dye-doped LC gels LC gels and provide several methods to improve the colors. One application of electrically tunable iris is also demonstrated.
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Liao, Chia-Huang, and 廖家煌. "Application of New Black Dichroic Dyes in Polarizer-Free Liquid Crystal Devices." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/20534425171401585298.
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碩士<br>國立交通大學<br>光電工程學系<br>100<br>Black dichroic dyes doped in LC materials increase the contrast ratio of LC devices. In this reseach, black dichroic dyes were prepared and applied to polarizer-free LC devices. The absorption spectrum of the black dichroic dyes PC B1 covers the entire visible range, which solves the light leakage issue of the commercialized black dichroic dyes S428 (from Mitsubishi, Japan) due to weak absorption in blue.
5 kinds of dichroic dyes with different absorption spectra were mixed to prepare black dichroic dyes PC B1 (Y1 : AZO1 : AR1 : AB4 = 1.0 : 0.85 : 1.8 : 2.5) and PC B2 (Y1 : AZO1 : AO1 : AB4 = 1.0 : 0.7 : 4.7 : 3.9). Between these two black dichroic dyes, PC B1 having uniform absorption spectrum covering the entire visible range is doped in TN LC devices to study the electro-optical properties and then applied to polarizer-free LC devices. Polymer-stabilized cholesteric texture (PSCT) is applied as the polarizer-free LC device in this reseach. The PC B1 doped in PSCT device increases the contrast ratio from 6:1 to 19:1 comparing with pure PSCT devices and has continuous gray scales with 5.44 ms fast LC response.
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Tai, Tu-Chun, and 戴土鈞. "The improvement of manufacturing process in a polarizer of the liquid crystal display." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/27006207545784144132.
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碩士<br>義守大學<br>資訊管理學系碩士在職專班<br>99<br>Polarizer is the key component of Liquid Crystal Display. In these years, because of the financial turmoil, companies have realized that there will be a business crisis for the management in the future. Now, for the industry of the polarizer of Liquid Crystal Display,the biggest problem is how to innovate and persevere the capacity of the company when the added value and margin are being reduced due to the competition from the same business. The research also finds out the value and improvement in the company of Liquid Crystal Display of the polarizer can be excepted within the complete combination of manufacturing and manpower allocation, the analysis of the motion process, the elimination of unnecessary manufacturing motion and cost, and the adjustment of production system. The research is to confer the spirit and the production system of Toyota Production System improves the production process of the polarizer of Liquid Crystal Display by reviewing the literature about Toyota Production System. When the company has its own core technology, the cost of manufacture could be reduced .Then the innovation can continue under the vision and guiding policy of the company. At last, the company could continue forever to manage.
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Komanduri, Ravi K. "Ultra-efficient liquid crystal projection displays polarizer-free displays using continuous polarization gratings /." 2009. http://www.lib.ncsu.edu/theses/available/etd-05042009-201633/unrestricted/etd.pdf.
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Chen, Zhi-Bin, and 陳志斌. "High Contrast Ratio and Low Driving Voltage of Polarizer-free Liquid Crystal Mode." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/34911812506901868801.
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碩士<br>國立交通大學<br>顯示科技研究所<br>102<br>The recemizable chiral dopant was applied in the reversed-mode polymer-stabilized cholesteric texture (PSCT). The chiral dopant was racemized by thermal process, the elastic energy from the chiral dopant would be reduced, this will cause lower threshold voltage and fast response time. Due to the anchoring effect of the polymer network on the LC molecules, the LC would tend to become the CLC structure even if the chiral dopant has been fully racemized. The contrast ratio is maintained as the initial value. Additionally, the CLC structure presented gradient pitch during the racemization process and resulted in higher contrast ratio, in this time, the operating voltage was operated between the one fully racemized and without racemized.
In this thesis, the influence of LC host, UV intensity, cell condition, chiral dopant and polymer concentration on electro-optical properties are discussed. Under appropriate conditions, the PSCT devices decrease the 30~40 percent threshold voltage when chiral dopant fully racemized. The contrast ratio can be achieved 12.3:1 when chiral dopant is partially racemized.
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Shih, Bing-Hong, and 施秉鋐. "High-efficiency Polarized Light Illumination System for Liquid-Crystal-Display Projectors." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/89021141389001382112.
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碩士<br>逢甲大學<br>電機工程所<br>98<br>This research use the polarization optics and ZEMAX optical design software to design the light polarization conversion components which fully convert the polarization state of light for the illumination light of the projection system. This research use ZEMAX optical design software to design the polarization conversion components, and analyze the illumination and parallelism of light by TRACEPRO analysis software for finishing the design of high-efficiency polarized light illumination system in the LCD projector. The system specification are: 46 mm × 40 mm × 5 mm、the material of all the lens are BK7 and light source wavelength is 546.1 nm. The light doesn’t pass through PBS and wave retarder, its irradiance is 13.395 watts (44.65%); and the light pass through PBS and wave retarder with power(focal length is equal to 5 mm ), its irradiance is 19.007 watts (63.35%). This study not only demonstrated that through the reflector and the polarization conversion element can effectively improve the efficiency from 44.65% to 63.35%, but also constructed a compact light illumination system in the LCD projectors.
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Ching-YiHuang and 黃靜宜. "Study of patterned electrodes to realize liquid crystal lenses with linearly polarized independent characteristics." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/01301225774467528971.
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碩士<br>國立成功大學<br>光電科學與工程研究所<br>98<br>In this thesis, we mainly study using patterned electrodes to realize liquid crystal lenses with linearly polarized independent characteristics. The patterned electrodes provide a symmetric non-uniform electrical field, which drives the director orientation of spatial liquid crystals in order that suitable distribution of gradient refractive indices can be achieved in the cells. When an incident light beam passes through the cell, light beam can be converged or divergent according to the conditions of optical path difference generated by refractive index distribution. In this experiment, we use three patterned electrodes to manufacture liquid crystal lenses, including circular hole-pattern liquid crystal lens, point-pattern liquid crystal lens and blu-ray-pattern liquid crystal lens. Observe optical performances of these lenses with distinct liquid crystal and alignment in different voltages, such as interference stripes figure and focal length measurement.
Experimental results demonstrate that patterned electrodes to realize liquid crystal lenses with linearly polarized independent characteristics can be achieved by using distinct liquid crystal and alignment.
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Chen, Jun-Lin, and 陳俊霖. "A polarizer-free reflective display based on droplet manipulation on a liquid crystal and polymer composite film." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/15991468731775552952.
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碩士<br>國立交通大學<br>顯示科技研究所<br>98<br>A novel reflective polarizer-free display realized by controlling the wettability of a liquid crystal and polymer composite film (LCPCF).The wettability of the LCPCF changes because of the electrically tunable orientation of the liquid crystal directors anchored among the polymer grains. We can manipulate a movable color droplet on the LCPCF by a wettability gradient owning to the distribution of electric field. To realize a reflective polarizer-free display, we put a hole -patterned black matrix above the LCPCF. The color of the light passing through the hole changes as the color droplet moves. In this paper, we analyze the mechanism of the droplet movement on the LCPCF by form the surface morphology and the surface tension properties. We also discuss the effects of the applied pulse voltage and the thickness of the LCPCF on the performance of the display. The characteristics of this display are color-filter-free, polarizer-free, wide viewing angle, bistable and reflective operation, thus it is suitable for the application of e-paper. Other potential applications of the LCPCF are liquid lenses, bio-sensors, and microfluidic devices.
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Lin, Taiy-In, and 林泰印. "Effects of hygrothermal deformation of polarizer components on light leakage in thin-film transistor liquid-crystal displays." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/92289089306390918978.
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博士<br>國立交通大學<br>材料科學與工程學系所<br>103<br>In this study, we combine the stress measurement using bending beam technique with static thermal-dependent and transient time-dependent three-dimensional (3D) finite element analysis (FEA) analysis to examine the light leakage variation of the thin-film transistor liquid-crystal display (TFT-LCD) panel. The objective is to understand the effects of material properties of key components, temperature, and humidity under hygrothermal reliability test on the light leakage phenomena. The shrinkage stress in stretched poly(vinyl alcohol) (PVA) film and stress relaxation ability of pressure-sensitive adhesives (PSA) layers are found to be the key factors determining the stress distribution and out-of-plane displacement of a polarizer stack. For hard-type PSA, its polarizer stack generates the highest bending curvature with maximum out-of-plane displacement but minimum in-plane displacement, leading to anisotropic stress distribution with high stress around the edges. On the other hand, polarizer stack with soft-type PSA yields the maximum in-plane displacement but the minimum out-of-plane displacement, resulting in isotropic stress distribution.
3D FEA shows that a strong correlation exists between light leakage and retardation difference induced by stress on triacetyl cellulose (TAC) films. For hard-type PSA, the area of higher principal stress difference is relatively small and localized on the edges of the panel, thus indicating low dimensional variations. In contrast, funnel-type light leakage and greater polarizer shrinkage are found for soft-type PSA. Moreover, the magnitude of hygroscopic stress in the simulated analysis is found to be significantly higher than that of thermal stress. This can be attributed to moisture’s plasticizing effect on the hydrophilic polymers such as PVA and PSA layers, leading to enhanced stress relaxation and degradation of the display image quality. An increase in Young’s modulus of PSA brings in lower relaxation ability and better resistance to shrinkage in polarizer stack, making it an effective solution to minimize the light leakage. The other effective solution is to develop a TAC film with lower Young’s modulus and/or lower coefficient of thermal expansion (CTE).
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Chang, Hsuan-Ting, and 張瑄庭. "Fabrication and Characterization of Photonic Crystal for Self-assembled Block copolymers using Polarized Light Illumination." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/qs4aj3.
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碩士<br>國立中山大學<br>材料與光電科學學系研究所<br>107<br>Abstract
This paper invents a new process technology to fabricate 1D photonic crystals, which uses polarized light to induce high-molecular block copolymers to exhibit periodic structure. The photonic crystal prepared by this method has higher regularity than the traditional process technology. By using the polarization inducing technique of the present invention, it is only necessary to add a linear polarization exposure process during the film formation process to induce the polar functional groups to be aligned in a specific direction, thereby forcing the hydrophobic groups along the polar groups. In the film formation, the 1D periodic arrangement is achieved, and the processing such as solvent
annealing and substrate modification is not required, thereby simplifying the manufacturing cost.
The method used in this study is to use PS-P2VP as the core material, and then use the solvent casting method and the linearly polarized laser light to form a periodic structure. In order to evaluate the influence of molecular weight and the wavelength and intensity of polarized light on the periodic alignment, this paper uses linearly polarized light with different molecular weights and different wavelengths and intensities to detect the structure and period of the film through a TEM and a SAXS instrument.
In addition, in this paper, the ionic liquid is added into the film, which selectively wets the P2VP segment, increases the P2VP spacing, and makes the period satisfy the Bragg diffraction condition of visible light, and the diffraction efficiency can reach 40%. The opportunity to expand the use of polymers in communications and filtering applications
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Li, Jia-Hau, and 李家豪. "Electro-opto controllable aperture for linearly polarized lights using double twisted nematic liquid crystal cells." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/89b49x.
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碩士<br>國立中央大學<br>光電科學與工程學系<br>106<br>In this study, the poly(9-vinylcarbazole) (PVK) was adopted to be the planar alignment layer for a twisted nematic liquid crystal (TNLC) cell. Combing the photoconductive property of PVK and the polarization rotation property of TNLC, the fabricated TNLC cell can be applied as an electro-opto controllable LC aperture for linear polarized lights. The electrical control by an applied DC voltage and the optical control by a UV light illumination make the controllable aperture size of the ring-like aperture (normally white state) and the spot-like aperture (normally black state). The controllable range of aperture diameter is based on the spot size of UV light.
In addition to the demonstration of LC aperture by a single layer 90˚-TNLC, this study also proposes that the combined two 45˚-TNLC cells, also known as a tandem 90˚-TNLC, can improve the performances of the electro-opto controllable LC aperture. The basic concept of the tandem 90˚-TNLC is the self-compensation of the undesirable phase retardation. Hence, the degree of linear polarization (DoLP) value of the output beam and the transmittance after passing through an analyzer can be significantly improved. In other word, a LC aperture based on such a tandem 90˚-TNLC cell is independent of wavelength and the direction of the polarization of the incident light so that the LC devices have high potential for practical applications.
The relationships between the polarization directions of the incident linearly polarized light and the DoLP values of output beams through a single layer 90˚-TNLC and a tandem 90˚-TNLC have been examined experimentally. Moreover, the transmittance spectra in the visible range of the output beam through the analyzer for these two cases of TNLC devices have also been discussed. According to the experimental results, the tandem 90˚-TNLC is more widely applicable than the single 90˚-TNLC due to its properties of independences of wavelength and the direction of input polarization. Finally, the LC aperture can be applied to combine with the properties of light shutters according to the electrical switching. By controlling the conditions of UV illumination and the applied DC voltage, the dose of light can be controlled by such a LC shutter.
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Chen, Chien-Chuan, and 陳建銓. "Optical Design and Analysis of Nanostructure Polarized Light Guide Illumination Module for Liquid Crystal Display." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/89960522229008832986.
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Chiang, Tsung-Han, and 江宗翰. "A Polarizer-free Electro-optical Switch Using Dye-doped Polymer-Stabilized Blue Phase Liquid Crystals." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/21603297735127424608.
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碩士<br>國立交通大學<br>光電工程學系<br>99<br>We successfully demonstrated a polarizer-free electro-optical switch using dye-doped polymer stabilized blue phase liquid crystal, or DDPSBP-LC. The operating principle is: at voltage-off state, the dye molecules and liquid crystal form the structure of the double twist cylinders. As a result, the DDPSBP-LC is in dark state due to the combination of Bragg reflection, scattering and light absorption. At the voltage-on state, the blue phase structure is unwound locally. The DDPSBP-LC is then in bright state because of the small light absorption only. The bright state and dark state of DDPSBP-LC is polarizer-free. We measured the electro-optics properties, the polarization dependency, the temperature effect of DDPSBP-LC. DDPSBP-LC electro-optical switch have the advantage of polarizer-free, alignment-layer free, high reflection, simple electrode design and fast response time. The other electro-optical applications of DDPSBP-LC are dimming mirror, 3D shutter glasses, etc.
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Huang, Jyh-Bang, and 黃志邦. "The Study of Liquid-Crystal Molecular Alignment by Linearly-Polarized Ultraviolet(LPUV) Light Exposed Polyimide Films." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/28308823675239304006.
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碩士<br>國立交通大學<br>光電工程研究所<br>85<br>The liquid-crystal ( LC ) molecular alignment phonomenon using buffed polyimides was discovered by Maugin in 1911. However, the detailed mechanism and related parameters of rubbing are not yet understood perfectly. Moreover, this method can cause some problems, such as the generation of electrostatic charges and dust or the destruction of Thin-Film-Transistor (TFT) in active matrix Liquid-Crystal Displays ( AM-LCDs ).
Recently, it is very popular in non-contact alignment method using Linearly-Polarized Ultraviolet ( LPUV ) light exposure. In this thesis, we utilize three kinds of commercial polyimides which are JSR AL-1254, JSR AL-3046 and NISSAN SE-3140 for experiment. The surface optical anisotropy and the LC molecular alignment by using Fourier Transform Infrared ( FT-IR ) spectrometer, optical retardation measurement, LC pretilt angle measurement and crossed-polarizer transmittance measurement were studied.
The experimental results showed that the chemical structures of polyimides changed because of absorbing energy after LPUV light exposure. From optical retardation measurement, the surface optical anisotropy grew more and more obviously during LPUV light exposure. Finally, we used a model and a theory to explain this phenomenon.
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Chiang, Yi-Lun, and 江宜倫. "Biosensing for Protein and Immunocomplex Detection Using Dye-Doped Liquid Crystals and Polarized Light." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/7kjpm7.
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碩士<br>國立交通大學<br>光電系統研究所<br>106<br>Liquid-crystal (LC)-based biosensors have been intensively exploited in recent years. The basic principle of them originates from the high susceptibility of LC orientation to external stimuli that produces a rapid and easily-visualized response of its birefringence as well as optical anisotropy to the change of surface alignment. However, from point of view of quantitation in the amount of biomolecules, it is difficulty in estimating the correlation of biomolecular concentrations to the brightness of corresponding optical textures. In considering with the absorptivity of dichroic dye, a quantitative protein assay using dye-doped liquid crystal (DDLC) as the sensing platform was developed. In this study, a black dye with high dichroic ratio and wide absorption band was used as the dopant in the DDLC mixture to promote the sensitivity of the biosensing system.
Results based on transmission spectra indicate that the concentrations of the commonly used protein standard bovine serum albumin (BSA), ranging from 106 to 102 g/ml are detectable through the changes in the transmittance. When the concentration of BSA is lower than 106 g/ml, the amount of biomolecules isn’t enough to disturb the alignment of DDLC, the dye and LC molecules stay vertical to the substrate plane due to the use of DMOAP as the alignment layer. The absorbance of the non-BSA DDLC cell is minimum and it yields the highest transmittance. In contrast, the alignment of dye and LC molecules would be disturbed when BSA is immobilized on the DMOAP-coated substrate. In considering the dichroic properties of dye molecules, the benefit of adding a linear polarizer specific for the spectral measurements of the DDLC is that the sensitivity of detection of optical signal can be essentially enhanced when adjusting the transmission axis of the polarizer to become parallel to the rubbing direction for initial LC alignment. In comparison with transmission spectra as measured by natural (i.e., unpolarized) light, the black dye can absorb the linearly polarized incident light more effectively when the electric field vibrates along the principle axis of the dye. To examine quantitatively the concentration of BSA molecules based on optical features of the DDLC, we developed a parameter Treduced, which is the relative reduction in transmittance between its maximum and minimum values. In other words, this equation is defined as differences between the highest and the lowest absorption (i.e., T and T||) divided by the highest absorption at various concentration of BSA.
With the inspection utilizing BSA as the tested biomolecules of this system, we extend our investigate target to CA125 antibody antigen immunocomplex, we examined the performance of CA125 antibody complexed with BSA solutions as the tested antigen under polarized optical microscope and white light spectrometer. The results suggest that the nonspecific BSA in antigen was unable to complex with the CA125 antibody and thus we can prove that the system exists specificity. On the other hand, we complexed various concentrations of CA125 antigen with fixed CA125 antibody. We can find that the transmittance gets decreased with increasing CA125 antigen concentration. According to these results, the transmittance of the DDLC samples can be correlated with CA125 concentration and this system can be established for cancer screening assay.
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Lin, Chun-Min, and 林俊民. "The Polarized Beam Splitter from an Ideal Liquid Crystal Generated by a Uniform Electric Field through Patterned Electrodes." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/33119788106042545124.
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碩士<br>國立清華大學<br>光電工程研究所<br>95<br>A PBS from an idea LC was demonstrated by the structure with double-sided patterned electrodes biased by a uniform electric field. The binary phase grating was formed by two periodically arranged indium-tin-oxide (ITO) stripes. Adjusting the applied voltage, the orientation of LC molecules was controlled by the patterned ITO electrodes and resulting with a phase difference occurring between two domains embodying in achieving applications for diffractive devices.
In this work, E7 and MJ041937 (VA) liquid-crystal materials were prepared. For MJ041937 (VA), diffraction efficiencies of the zero and the first order were performed with results of 1~2% and 40% respectively. Whereas, for E7, diffraction efficiencies of the zero and the first order are 0.1%~0.5% and 40% respectively. However, these devices demonstrate advantages of no scattering, and no diffraction during no applying voltage, a spread selection in input wavelengths, low voltages and retaining the original polarization without applying field for MJ041937 (VA)
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You, Jan-Wen, and 游展汶. "Measurements of the Ordinary and the Extraordinary Refractive Indices of a Birefringent Crystal by Circularly Polarized Heterodyne Interferometry." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/09128744206908137419.
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碩士<br>國立交通大學<br>光電工程所<br>88<br>Birefringent crystals are often used to fabricate many optical devices, such as birefringent prisms and wave plates. In this thesis, a method for measuring the ordinary and the extraordinary refractive indices of a birefringent crystal by using circularly polarized heterodyne interferometry is presented. Firstly, a linearly polarized laser with an electro-optic modulator and a quarter-wave plate is used to act as a circularly polarized heterodyne light source. Next, according to Jones calculus and the reflective characteristics of the birefringent crystal, the test signal intensity with a cosine wave form can be obtained after the light reflected from the crystal passes through an analyzer. The phase differences between the reference beam and the test beam are the function of the azimuth angle of the crystal and the incident angle, and the ordinary and the extraordinary refractive indices can be estimated simultaneously by substituting the measured values of phase differences into the above function. Because only the reflective characteristics of a light beam are used, the thickness and the surface flatness of the test material are not required. In addition, it is very stable and has high resolutions owing to its common-path heterodyne interferometric structure.
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Lin, Chun-Hao, and 林俊豪. "The Analysis and Calculation for the Polarized X-ray Absorption Spectra near the Curie Point in BaTiO3 Single Crystal." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/18433086774623039428.
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碩士<br>國立新竹教育大學<br>應用科學系碩士班<br>96<br>It is to calculate the XANES with the difference crystal lattice structure by changing the electronic structure which are paraelectric cubic and ferroelectric tetragonal with the FDMNES program. The major is to discuss the difference lattice with the electronic structure in XANES and compare the polarize XANES to explain the change of electronic structure in transition of BaTiO3.
The FDMNES program is in using the Density Functional Theory to calculate the energy steady state in sample. By the density of state to get the cross section of XANES. At the first, it’s to use the lattice constant of cubic and tetragonal in experiment which approach the phase transition temperature and the almost equivalent unit cell volume that will be had directly effect to match the calculate XANES and the experimential XANES. The experimential polarize XANES can clearly show the difference electronic structure in the different lattice by change the parameter in the FDMNES to expect and explain the characteristic in near-edge structure. The thesis describe how to start calculating and how to use parameter in FDMNES. Including how to adjust electronic structure in atoms which can be the ionic and Fermi level, radius.Finally, we can judge the polarize by the diffraction plane and the azimuth angle.
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Chen, Yuan-Di, and 陳園迪. "Studies of azo dye adsorption effect induced by elliptically polarized light in azo dye-doped liquid crystals." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/50562811800075455393.
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碩士<br>國立成功大學<br>光電科學與工程研究所<br>97<br>This thesis studies the alignment properties of liquid crystals by the adsorbed azo dyes (methyl red; MR) excited by elliptically polarized green laser beams with various ellipticities in azo dye-doped liquid crystals (ADDLCs). Firstly, an elliptically polarized green laser beam with its major axis being parallel to the liquid crystal director was used as the pump beam. Experimental results showed that MR molecules were adsorbed along multiple directions due to the symmetry light-absorbance by MR molecules. In other words, multi-domain adsorption was generated. Secondly, by overcoming the shortage of multi-domain adsorption, the major axis of the pump beam was changed to make an angle of +45o with the liquid crystal director. In this part, the alignment properties of the adsorbed MRs generated by illuminating elliptically polarized green laser beams with various ellipticities having a fixed light intensity or a fixed light component along the direction of major axis were studied. The experimental results indicated that the light-induced MR molecular reorientation effect, the so-called twisted angle, caused by the adsorbed MR, decreased with increasing ellipticity of the elliptically polarized green light. Notably, zero pre-tilt angle of LC alignment was achieved in this experiment. Thirdly, the MR adsorption effect recorded by circularly polarized green laser beams with various intensities was studied. Experimentally, neither the twisted angle nor the tilt angle was produced using circularly polarized green light. Additionally, the nucleation phenomenon, which caused a nonuniform adsorption layer was observed. Finally, the direction of the MR adsorption was found to be independent of the sign of the light ellipticity, but dependent on the direction of the major or minor axis of the elliptically polarized green pump beam. Moreover, the ripple structures of the adsorbed dyes, which were observed using a linearly polarized green pump beam were not observed in the cases pumped by elliptically or circularly polarized beam.
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Mack, Patrick [Verfasser]. "2D H-polarized auxiliary basis functions for the extension of the photonic Wannier function expansion for photonic crystal circuitry / von Patrick Mack." 2011. http://d-nb.info/1012674371/34.
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Ménard-Tremblay, Pierre. "Synthèse et caractérisation de complexes métalliques de ruthénium, fer et cobalt à base des ligands terpyridine et bipyridine pour l'obtention de cristaux liquides." Thèse, 2008. http://hdl.handle.net/1866/7808.
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Taubitz, Christian. "Investigation of the magnetic and electronic structure of Fe in molecules and chalcogenide systems." Doctoral thesis, 2010. https://repositorium.ub.uni-osnabrueck.de/handle/urn:nbn:de:gbv:700-201006096312.
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In this work the electronic and magnetic structure of the crystals Sr2FeMoO6,
Fe0.5Cu0.5Cr2S4, LuFe2O4 and the molecules FeStar, Mo72Fe30, W72Fe30 are investigated
by means of X-ray spectroscopic techniques. These advanced materials exhibit very interesting properties like magnetoresistance or multiferroic behaviour. In case of the molecules they also could be used as spin model systems. A long standing issue concerning the investigation of these materials are contradicting results found for the magnetic and electronic state of the iron (Fe) ions present in these compounds. Therefore this work focuses on the Fe state of these materials in order to elucidate reasons for these problems. Thereby the experimental results are compared to multiplet simulations.