Dissertations / Theses on the topic 'Nematic layer'
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Pardaev, Shokir A. "LIGHT SCATTERING STUDIES OF DEFECTS IN NEMATIC/TWIST-BEND LIQUID CRYSTALS AND LAYER FLUCTUATIONS IN FREE-STANDING SMECTIC MEMBRANES." Kent State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=kent1497022792130101.
Full textВоробйов, Владислав Євгенійович. "Оптичні рідкокристалічні сенсори." Bachelor's thesis, КПІ ім. Ігоря Сікорського, 2020. https://ela.kpi.ua/handle/123456789/35117.
Full textThesis is devoted to improving the efficiency of one of the main executive elements of electronics. Introduction to the main characteristics of sessors. Analysis of ways to optimize the technical parameters of liquid crystal pressure gradient sensors. Analysis of liquid crystal sensors of acceleration, vibration and inclusion. The paper considers many types of sensors and prefers the optical liquid crystal sensor due to the easy unification of its construction and widespread use in the home. Using the properties of liquid crystal materials, it was possible to achieve extremely sensitive sensing sensors.
Lindsay, R. I. "Shear in nematic liquid crystal layers." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296747.
Full textMottram, N. J. "Boundary effects in nematic liquid crystal layers." Thesis, University of Bristol, 1996. http://hdl.handle.net/1983/3f718f68-e280-4994-afa2-29a7845c73f7.
Full textMcLaren-Jones, Jennifer Sian Elizabeth. "Band edge lasing in chiral nematic liquid crystals." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/288382.
Full textHällstig, Emil. "Nematic Liquid Crystal Spatial Light Modulators for Laser Beam Steering." Doctoral thesis, Uppsala University, Quantum Chemistry, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4693.
Full textLaser beam control is important in many applications. Phase modulating spatial light modulators (SLMs) can be used to electronically alter the phase distribution of an optical wave-front and thus change the direction and shape of a laser beam. Physical constraints set limitations to the SLM and an ideal phase distribution can usually not be realised. In order to understand how such components can be used for non-mechanical beam control three nematic liquid crystal (NLC) SLMs have been thoroughly characterised and modelled.
The pixel structure and phase quantisation give a discrepancy between ideal and realised phase distributions. The impact on beam steering capability was examined by measurements and simulations of the intensity distribution in the far-field.
In two of the studied SLMs the pixel period was shorter than the thickness of the LC layer giving the optical phase shift. This results in a so-called “fringing field”, which was shown to degrade the phase modulation and couple light between polarisation modes. The deformation of the LC was simulated and a finite-difference time-domain (FDTD) algorithm was used to calculate how polarised light propagates through the optically anisotropic SLM.
Non-mechanical beam steering and tracking in an optical free-space communication link were demonstrated. Continual optimisation of the steering angle was achieved by feedback from a video camera.
The optical properties of the SLM in the time period right after a voltage update were studied. It was shown how light is redistributed between orders during the switching from one blazed grating to another. By appropriate choice of the blazed gratings the effects on the diffraction efficiency can be minimised.
The detailed knowledge of the SLM structure and its response to electronic control makes it possible to predict and optimise the device performance in future systems.
Hällstig, Emil. "Nematic liquid crystal spatial light modulators for laser beam steering /." Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4693.
Full textShasti, Mansoureh. "NEMATIC LIQUID CRYSTAL GUEST-HOST SYSTEM FOR EYEWEAR ANDRANDOM LASER APPLICATIONS." Kent State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=kent1556626607581832.
Full textTope, Bryan Keith. "Controlling optical beams in nematic liquid crystals." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/29634.
Full textRumbaugh, Scott Hamilton. "Endless state-of-polarization control for coherent optical communication systems using nematic liquid crystals." PDXScholar, 1989. https://pdxscholar.library.pdx.edu/open_access_etds/4145.
Full textSenyuk, Bohdan. "Dielectric Response of Liquid Crystals Formed by Bent-Core and Chiral Molecules." Kent State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=kent1290017391.
Full textLin, Yu-Ting, and 林育霆. "Optical properties of one-dimensional photonic crystal with a twisted-nematic defect layer." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/58d3us.
Full text中原大學
奈米科技碩士學位學程
99
This thesis reveals the optical properties of a one-dimensional photonic crystal with a twisted-nematic liquid crystal defect layer. The one-dimensional photonic crystal is formed from two dielectric materials with different refractive indices by means of periodically alternate evaporation deposition. As the defect layer, the alignment and orientation of the twisted-nematic liquid crystal is mediated by the alignment technique as well as an externally applied voltage. To comprehend the optical and electro-optical properties, a spectrometer is adopted in order to observe the transmittance in the visible spectrum from 400 to 800 nm. The results show that both sets of defect modes attributed to the extraordinary and ordinary components coexisting when a polarizer controlling the polarization of the incident beam is used. These two distinct sets of peaks switch between each other when the polarization angle is altered. All defect-mode peaks blueshift with increasing applied voltage. Besides, the crossed-polarizer examination reveals the polarization-selection effect and multiple interferences. Owing to the birefringent retardation and the polarization waveguiding in a mixed-mode twisted-nematic liquid crystal, a hump-like spectral undulation appears and affects the height of the defect-mode peaks. The superposition of the humps and peaks brings about the selection effect, which dramatically enhances the transmittance of the defect-mode peaks located at the middle of the humps while suppresses most peaks impartially to as low as 20% and diminishes the one sitting right in the hump valley has nearly no transmittance. The results of experiments and simulations, being in good consistence with each other, demonstrate that such a device may be used as an electrically controllable very-narrow-band monochromatic selector.
Archibald, Aaron, and 艾倫. "Modeling and simulation of a one-dimensional photonic crystal with a twisted nematic defect layer." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/58824998534522282735.
Full text中原大學
奈米科技碩士學位學程
100
Liquid crystals flow like liquids yet possess either or both positional and orientational order, such as a solid crystalline material would. They exhibit both dielectric anisotropy, allowing their orientation to be controlled by an applied external field, and optical anisotropy, allowing them to change the polarization of light transmitting through them. Many stable organizations of liquid-crystal (LC) molecules are realized with the assistance of polymer alignment layers, anchoring the orientation of LC molecules at the domain boundaries. These properties are utilized to create high quality LC displays widely available in the market today. However, the development and application of LC materials for display devices is a well-established and maturing field, leading researchers to investigate other possible applications of this versatile state of matter. This work is a result of the ongoing search for tomorrow’s LC technology, exploring the use of a LC material in a twisted-nematic (TN) configuration as a field-controllable defect layer within a onedimensional (1D) photonic crystal (PC). The 1D PC structure is a stack of alternating layers of two dielectric materials. Reflections at each interface of the PC structure create interference patterns based on the thickness and refractive index of each layer of the device. These parameters are designed accordingly to yield a desired overall transmission through the multilayer structure. The inclusion of a LC layer adds new functionality to this structure, providing a method for tuning the spectral properties of the device and contributing an ability to rotate the polarization ofpropagating light. These new features of the hybrid PC/LC device are attractive for application where control of the intensity or polarization of light is required, opening the door for a possible new application of LC materials. Many configurations of a twisted-nematic (TN) defect layer within a 1D PC are yet unexplored. In the same way the TN configuration developed over time for display application, the twisted-nematic layer within a PC must be investigated. This study develops models for calculating the transmission of light through layered isotropic materials, such as the PC structure, as well as through the TN layer. The transmission through the composite device may then be predicted though simulation. The transmission of each component of the device is modeled by calculating the thickness of each material layer, fitting the transmission curve of each component. It is shown that this technique can be used to estimate the thickness of the LC layer within the PC structure as well as provide accurate predictions for the transmission of light through a hybrid PC/TN device having arbitrary twist angle and input polarization. Further experimental data collected from test cells demonstrate the optical properties of several PC/TN schemes. It is found that simulation results closely match experimentally obtained data, and the devices may serve well as wavelength selectors, filters or intensity modulators.
LI, WEI, and 李偉. "Acousto-optic effect induced by ultrasound pulses in a free circular-edge nematic liquid-crystal layer." Thesis, 1987. http://ndltd.ncl.edu.tw/handle/12411000307246112182.
Full textChin-LungLin and 林進龍. "Evaluation of surface azimuthal anchoring energy between grating surface and nematic liquid crystal layer using geometric model." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/ej77k2.
Full textHuang, Da-Yan, and 黃達彥. "Bistability in a Nd:GdVO4 laser withintracavity twisted-nematic liquid crystal." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/85334422248812369905.
Full text逢甲大學
光電研究所
96
We study optical bistability in a Nd:GdVO4 laser with intracavity twisted-nematic liguid crystal. The bistable region can be controlled by the applying voltage and the rotating alignment angle of the twisted-nematic liguid crystal. The quasi-periodic, self-pulsing and chaotic dynamics were observed in this region. Moreover, the spatial distributions and the temporal dynamics strongly depended on the pumping profiles.
Shen, T. L., and 沈宗麟. "Laser heating and spatial self-phase modulation effect in nematic liquid crystal film with Nd:YAG laser light." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/18231851517899518999.
Full text國立交通大學
電子物理學系
83
We disscuss that the laser heating effect can add the maximun rotion angle of liquid crystal within 1.06 micron metter Nd:YAG laser. By the measurement of the diffraction patterns induced by the spatial sefl-phase modulation effect it can help us to realize the temperature icrement of the sample. We found that there was Freederiscksz transition and the threshold insity consistent with our calculation. The number of rings that we measured was fewer then we calculated.
CHEN, DIAN-RONG, and 陳殿榮. "Multiorder differaction of laser induced phase grating in a nematic liquid crystal film." Thesis, 1988. http://ndltd.ncl.edu.tw/handle/93870096486688629090.
Full textHUNG, LIN SHENG, and 林聲宏. "Manipulation of random laser from dye-doped twisted nematic liquid crystal within wedge cell." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/ws2r2d.
Full text國立臺北科技大學
光電工程系研究所
104
In this work, the orthogonal linear polarized random lasing beams was determined by the local director of LCs at two output plates from dye-doped twisted nematic liquid crystals (DD-TNLC) within the wedge cell. In addition, we also indicated that the resonant property of random laser can be successfully manipulated by means of a number of parameters, such as temperature, pump polarization and focused pump position. Through the thermal control, the lasing threshold of DD-TNLC laser decreased and slope efficiency increased with temperature while the operation temperature was below 25oC. At even higher temperature, the slope efficiency of random laser is declined because of thermal frustration. Besides, we controlled the output intensity of random laser through the orientation of the pump polarization relative to the rubbing direction at the incident plate. After spatially shift of the cell to vary the location of focused pump beam onto the cell with different thickness, we could also change the emission wavelength of DD-TNLC laser. In comparison with the FP laser, we demonstrated that the random laser reveal the lower speckle noise and higher discrimination after illuminating the Air Force test chart. All the measured results demonstrated that the controllable characteristics of DD-TNLC that will be practical used to the sensor, speckle noise suppression in some optical systems.
YANG, HONG-YU, and 楊弘宇. "Laser-pulse-induced molecular reorientation in nematic-liquid-crystal films with a free surface." Thesis, 1989. http://ndltd.ncl.edu.tw/handle/84479211601002927613.
Full textShen, Jen-Li, and 沈仁立. "Study on the Parameters Measurement of Nematic Liquid Crystal by Common-Path Dual-Frequency Laser Interferometer." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/85w9kt.
Full text國立臺北科技大學
光電工程系所
93
Common-path dual-frequency laser interferometer is employed to measure the parameters of nematic liquid crystal, including the phase variation of cell gap due to the applied voltage、the real phase change because of voltage、transmittance、response time、view angle、pretilt angle and cell gap. The result of experiment shows the data measured by common-path dual-frequency laser interferometer corresponds with the parameters given by manufacturer. Common-path heterodyne interferometer has many advantages, such as real-time measurement, hardly affected by the environment and vibration. The light source we utilized is Zeeman Laser which beat frequency is up to 2.6MHz and it provides the higher stability during the measurement. Additionally the optical structure of this experiment is much easier than the experiments which use other heterodyne light source structure.
"Nonlinear optical studies of laser induced reorientation and orientational photorefractive grating formation in nematic liquid crystals." 2006. http://library.cuhk.edu.hk/record=b5892810.
Full textThesis (M.Phil.)--Chinese University of Hong Kong, 2006.
Includes bibliographical references.
Text in English; abstracts in English and Chinese.
Song Liang = Xiang lie ye jing zhong ji guang shu gan ying de qu xiang zhong lian fei xian xing guang xue xiao ying he qu xiang xing guang zhe bian guang zha xing cheng / Song Liang.
Abstract --- p.i
论文摘要 --- p.iii
Acknowledgement --- p.iv
Contents --- p.v
Chapter Chapter 1 --- Introduction --- p.1
References --- p.5
Chapter Chapter 2 --- Brief review of liquid crystals and nonlinear optics of liquid crystals --- p.9
Chapter 2.1 --- Brief review of liquid crystals --- p.9
Chapter 2.1.1 --- General description --- p.9
Chapter 2.1.2 --- Types of liquid crystals --- p.11
Chapter 2.1.3 --- Order parameter --- p.14
Chapter 2.1.4 --- Liquid crystal alignment --- p.14
Chapter 2.1.5 --- Continuum theory of liquid crystals --- p.16
Chapter 2.2 --- Nonlinear optics of liquid crystals --- p.20
Chapter 2.2.1 --- Basic mechanism of nonlinear optics --- p.20
Chapter 2.2.2 --- Self-phase modulation --- p.23
Chapter 2.2.3 --- Orientational photorefractive effects --- p.29
Chapter 2.3 --- Sample preparation --- p.34
Chapter 2.4 --- Conclusion --- p.37
References --- p.39
Chapter Chapter 3 --- Domain formation in homeotropic nematic liquid crystal cell --- p.42
Chapter 3.1 --- Introduction --- p.42
Chapter 3.2 --- Domain formation under applied dc and ac electric fields --- p.44
Chapter 3.3 --- Light scattering of domains under applied dc and ac electric fields --- p.49
Chapter 3.4 --- Conclusion --- p.53
References --- p.54
Chapter Chapter 4 --- Laser induced self-phase modulation and effects of applied electric field --- p.56
Chapter 4.1 --- Introduction --- p.56
Chapter 4.2 --- Self-phase modulation without applied electric field --- p.58
Chapter 4.2.1 --- Experimental setup --- p.58
Chapter 4.2.2 --- Experimental results and discussions --- p.59
Chapter 4.3 --- Effects of applied electric field --- p.67
Chapter 4.3.1 --- Effects of applied dc electric field --- p.67
Chapter 4.3.2 --- Effects of applied ac electric field --- p.72
Chapter 4.4 --- Conclusion --- p.75
References --- p.77
Chapter Chapter 5 --- Orientational photorefractive grating in nematic liquid crystals --- p.80
Chapter 5.1 --- Introduction --- p.80
Chapter 5.2 --- Orientational photorefractive grating under dc electric field --- p.82
Chapter 5.2.1 --- Experimental setup --- p.82
Chapter 5.2.2 --- Experimental results and discussion --- p.84
Chapter 5.3 --- Orientational photorefractive grating under ac electric field --- p.90
Chapter 5.3.1 --- Raman-Nath grating --- p.90
Chapter 5.3.2 --- Quasi-Bragg grating --- p.96
Chapter 5.4 --- Conclusion --- p.98
References --- p.100
Chapter Chapter 6 --- Summary and future outlook --- p.103
List of Publications and Conference Presentations --- p.107
Huang, Jun-Wei, and 黃俊瑋. "Manipulation of random laser from dye-doped nematic liquid crystals inside capillary fiber through electric field." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/qt9e7a.
Full text國立臺北科技大學
光電工程系
106
In this dissertation, we demonstrated that the output characteristics of dye-doped liquid crystal random laser (RL) inside capillary fiber (CF) can be immediately controlled by the electric field. The heated DDLC mixtures were infilled inside two different kind of hollow core fibers, with core diameters of about 20 and 30 um, respectively, by the capillary effect. The prepared CF were sandwiched between two ITO glasses so that electric field can be applied to alternate the arrangement of the liquid crystal molecules inside the hollow cores. As applied AC voltage VAC increased, the enhancement of light scattering inside the LC mixtures were revealed by the light scattering spectrum and the image through the integration of polarization microscopy with the spectrometer and CCD. From the light scattering spectrum, the scattering intensity increased obviously as the VAC above 20 V and start to saturate as the VAC above 80 V. Through the pump of Q-switched laser, multiple emission spikes with narrow linewidth were immerged on top of pedestal with broad bandwidth that are attributed to the coherent and incoherent feedback. In addition, the variation of random lasing peak intensity as a function of VAC were consistent with the variation from light scattering spectrum. It demonstrated that the increase of output intensity from DDLC-RLs inside the CF was resulted from recurrent light scattering inside the LCs. Through the increase of applied voltage, the increase of slope efficiency and decrease of pedestal width of RL can also be efficiently and quickly controlled. In this work, we also use the Alpha-stable distribution to show the Lévy distribution of intensity fluctuation of DDLC-RL inside CF. The reduction of value from Alpha= 1.86 to Alpha = 1.59 was obtained without (VAC=0 V) and with applied voltage (VAC=60 V).
Lai, Chun-Hung, and 賴君紅. "Study on the phase retardation measurement of nematic liquid crystal by Zeeman dual-frequency laser interferometer." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/81579899444630154946.
Full text國立臺北科技大學
光電技術研究所
92
Since the LCD market is growing up rapidly, accurate measurements of the LCD parameters thus become more and more important. Since the molecular arrangement status of liquid crystal, as well as the status of optical propagation and polarization, is easily changed by external forces, in this thesis, we will proposed a zeeman dual-frequency laser interferometer system (model HP5529A) for the phase retardation measurement of nematic liquid crystal. Through the process of the phase measurements and the determinations of the LCD parameters using the measured phases, it is found that the proposed method is advanced over the conventional ones by high accuracy and stability and easy operation. By the way, the dual-frequency laser interferometer system’s merits of the wide range of frequency、the high resolution(nm)、the automatic system and the phase-time capture function also illustrated its optimum measured ability for measuring the structured parameters of LC cell.
Huang, Hsin-Yi, and 黃馨儀. "Investigation of Ionic Properties of Liquid Crystal and Polyimide-alignment Layers in Twisted Nematic Liquid Crystal Cells." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/mcn8a9.
Full text國立交通大學
影像與生醫光電研究所
103
In this thesis, we have studied ionic effects within rubbed-ITO-aligned and rubbed polyimide(PI)-aligned twisted nematic(TN)liquid crystal(LC)cells using a same nematic LC mixture. In our experiments, we have used heterodyne-phase-measurement method, and a LCR meter to measure the TN cells containing the same nematic LC mixture. The analytic equations were based on the ion generation and transport equations developed by T.-C. Chieu and K.-H. Yang for the investigation of ionic properties in ferroelectric LC cells. The ionic physical parameters of high-ionization-rate(HIR)and low-ionization-rate(LIR)impurities within the TN LC mixture and PI alignment layers were obtained by fitting experimental data to analytic equations. We have derived HIR and LIR ion concentrations, ionic mobility and activation energies of ions from ionic impurities in the TN LC mixture, and PI alignment layers. Good agreements between experimental results and theoretical analyses have been demonstrated. The results of our investigation have shown that both HIR and LIR ions existed in the rubbed-ITO-and rubbed-PI-aligned TN cells containing the same nematic LC mixture. The derived HIR and LIR ionic properties were different between the rubbed-ITO -aligned and the rubbed-PI-aligned TN cells implying that the PI alignment layers have contributed a substantial amount of ions for the latter. The methods reported in this thesis can explain the phenomenon of field-driven net mobile ions accumulated at the interfaces between the LC mixture and the PI alignment layers of the TN cell. With further investigations, we hope to apply our results to the identifications and reductions of ion generating chemical species within TN cells to improve the quality of TN LC displays.
Shiu, Siao-Ching, and 徐曉晴. "Investigation of Ionic Phenomena in the LC Mixtures and Rubbed Polyimide Aligned Layers of Twisted Nematic Liquid Crystal Cells." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/72441659321750987486.
Full text國立交通大學
影像與生醫光電研究所
101
Ion concentration, mobility and activation energy in liquid crystal cells are three most important parameters to affect the display qualities of LCDs in terms of threshold voltage, gray-level shift, charge holding ratio, flickers, image-sticking, and Mura. In this thesis, we, first, measured the phase relaxation of a TN cell under low-frequency voltage square wave at an amplitude equal to the middle gray level of the TN sample aligned by rubbed polyimide (PI) films at different temperatures to find out if the dominant ionic species are from the LC mixture (DMR, Depressed Molecular Reorientation) or from the PI layers (EMR, Enhanced Molecular Reorientation). Then, we used our newly developed methods to measure and analyze the data of voltage-holding-ratios (VHRs) of DMR and EMR TN cells at different temperatures to determine the ion concentration, the mobility and the activation energies of ion-dissociation rate of high-ionization-rate (HIR) and low-ionization-rate (LIR) impurities where the dominant ions were either from the LC mixture or PI layers of the TN cell. In the case that dominant ions were from the LC mixture of the TN cell, we have also determined the activation energies of ionic mobility of LIR impurities. Prior publications on the measurement of ion concentration and mobility did not distinguish ions either from HIR or LIR impurities. Our group have developed experimental and analytic methods to determine both mobility and ion concentration of HIR and LIR impurities in TN LCDs aligned by rubbed polyimide film, and found out recently that the dominant ionic species in LC mixture in a DMR sample came from impurities of low-ionization-rate(LIR). However, for the first time, we have also observed that both ions from HIR and LIR impurities existed in different DMR TN samples. We have also carried out the investigation for the case when an applied voltage of 5 V was applied to the DMR TN sample to orient the directors of LC molecules parallel to the applied electric field. However, the derived physical parameters on ions were quite different from those when 1 V was applied to the TN cell. In this thesis, we have observed and confirmed that ions from HIR and LIR impurities also existed in the rubbed PI alignment layers of TN cells exhibiting EMR behavior. For the first time in the world, we have successfully extended our methods of measurements and analyses to solve the EMR cases where the dominant ions are from the polyimide alignment layers of the TN cell. We have no knowledge where theses HIR and LIR impurities in the rubbed PI films came from. But we believe that, by applying our experimental and analytical methods reported in this thesis to investigate the TN cells made of LC mixtures of different concentration of key components and/or different PI material and process, we may find out the origins and the chemical structures of ions from HIR and LIR impurities existing in these EMR and DMR TN samples. The results of further investigation will lead us to develop PI alignment layers and LC mixtures without HIR and LIR impurities, and ultimately, the realization of low-power-consumption, high-display-quality TFT-LCDs free of flickers and image-sticking.