Twisted Nematic Liquid Crystal Device Research Articles

Quantum optical control experiment using Mach–Zehnder interferometer and twisted nematic liquid crystals

A Mach–Zehnder interferometer with an optical phase control by a twisted nematic (TN) liquid crystal (LC) device was studied. In a typical TN LC device, a change in the optical rotation state of π/2 can be obtained by applying a voltage of about 5 V with a cell thickness of several-micron. The TN cell is inserted into one optical path in the Mach–Zehnder interferometer. We obtained a pattern change when voltage was applied to the LC cell due to the change of the optical interference state. As a result, a change in the number of photons under weak light conditions is observed.

Nano P(VDF-TrFE) doped polyimide alignment layers for twisted nematic liquid crystal devices

ABSTRACTThe rapid development of consumer electronics and portable devices imposes a great demand for energy efficient information display systems. Among the information display devices, liquid crystal display (LCD) devices stands in the front. The fabrication of energy-efficient LCD systems demands new material and techniques. In this work, the conventional polyimide alignment layer of twisted nematic liquid crystal device (TNLCD) was replaced with ferroelectric polymer nanoparticle doped alignment layer. Morphology of the alignment layer was analysed using field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The ferroelectric nature of the polymer alignment layer was studied using dynamic contact electrostatic force microscopy (DC-EFM). TNLCD cells are fabricated with this modified alignment layer and the switching characteristics are compared with the conventional TNLCD devices. The TNLCD with modified alignment layer has shown a reduction of 50% in threshold (Vthr) and 47% reduction in saturation voltage (Vsat).

Broadband mid-infrared polarization rotator based on optically addressable LCs

This work proposes a mid-infrared polarization rotator that incorporates a twisted nematic liquid crystal (TNLC) cell with a photo-controllable alignment layer. The TNLC device with a sufficient phase retardation can act as an achromic polarization rotation device over a wide wavelengths range and thus can rotate the polarization of a mid-IR laser beam. The photo-alignment technique enables TNLCs with arbitrary twisting angles to be generated by the use of visible polarized addressing light to control the directors of the photo-alignment layer. Therefore, arbitrary rotation angles of the polarization axis of a linearly polarized mid-IR laser beam can be realized. Moreover, the rewritable property and reliability of this polarization rotator are experimentally verified. The flexibility of polarization control for broadband mid-IR opens up a large range of potential mid-IR applications.

Effect of ferroelectric nanoparticles in the alignment layer of twisted nematic liquid crystal display

The alignment layer of a conventional twisted nematic liquid crystal device (TNLCD) has been modified by doping it with ferroelectric barium titanate (BaTiO3) nanoparticles. The presence of uniformly dispersed ferroelectric nanoparticles in the alignment layer has enhanced the electro optical property of twisted nematic cell. The transmission-voltage characteristics show that the addition of BaTiO3 nanoparticle has reduced the Frederik's threshold voltage and saturation voltage. The dispersion of nanoparticles in the alignment layer was studied using scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). Nonlinear optical behaviour of the twisted nematic cell under different applied voltage is also investigated.

Analytical approach for unique determination of cell parameters and equivalent birefringent parameters of a generally twisted nematic liquid crystal device

In the measurement of a twisted nematic liquid crystal device (TNLCD) by an optical apparatus, the cell parameters of the TNLCD may result in multiple solutions in the measurement that all agree with the measured data; hence manufacturers cannot find a set of correct solutions from among the ambiguous ones. With the help of the optical equivalence theorem of a unitary optical system, the ambiguity of the measured parameters of a TNLCD, including cell parameters and equivalent birefringent parameters, can be simultaneously removed by an analytical approach using a single-wavelength polarimeter. The procedure for unique determination of the cell parameters is performed using a self-consistent condition to select a set of the correct solutions from all the possible solutions. The proposed method can be applied to characterize a generally TNLCD for which the twisted angle is close to 270° and the liquid crystal phase retardation is over 2π.

Preparation and Electrooptic Properties of Liquid Crystal Devices Doped with Cucurbituril-protected Gold Nanowires

Abstract Cucurbituril-protected gold (CB–Au) nanowires were prepared by ultraviolet irradiation of an aqueous sodium hydroxide solution of tetrachloroauric(III) acid in the presences of CB. The average width and length of CB[5]–Au nanowires were 256 and 6600 nm, respectively. The nanowires were dispersed in a liquid crystal, 4-cyano-4′-pentylbiphenyl, to construct a novel twisted nematic liquid crystal device (TN-LCD). The power consumption of this TN-LCD in the presence of CB–Au nanowires was lower than that in their absence.

Two-Dimensional Distributions of Five Cell Parameters of Twisted Nematic Liquid Crystal Device by Numerical Photometric Ellipsometer

A novel numerical photometric ellipsometer (NPE) under the condition of normal incidence and using a single wavelength laser beam is proposed wherein a continuously rotated quarter wave plate (QWP) at constant speed is required. To precisely measure the cell parameters of a twisted nematic liquid crystal device (TNLCD), the calibration of the QWP is necessary before measurement in this method. All five cell parameters of the TNLCD, namely, twisted angle, cell gap, rubbing angle, pretilt angle, and phase retardation, are obtained by least-square fitting of the measurement data versus the rotation angle of the QWP with the calculated intensity ratio of p- and s-polarization components according to our previously developed theory. The NPE can be extended to the two-dimensional distributions of all five cell parameters by using charge-coupled device (CCD) cameras. Experimentally, the results demonstrate the ability of the NPE to characterize the five cell parameters of the TNLCD in two dimensions with high accuracy and good repeatability.

Fast Electro‐Optic Switching of Twisted Nematic LCD Doped with Cyclodextrin Capped Silica Nanoparticles

AbstractWe prepared cyclodextrin (CyD)‐capped silica (CyD‐SiO2) nanoparticles and poly(cyclodextrin) (PCyD)‐capped silica (PCyD‐SiO2) nanoparticles. The average diameter of SiO2 nanoparticles capped by αCyD, βCyD, γCyD and PγCyD are 9.4, 8.4, 10.6, and 6.4 nm, respectively. The nanoparticles were dispersed in liquid crystal; 4′‐pentyl‐4‐cyanobiphenyl to construct novel twisted nematic liquid crystal device (TN‐LCD). The response time of this TN‐LCD in the presence of PγCyD‐SiO2 nanoparticles was faster than that in the absence.

Two-Dimensional Distributions of Five Cell Parameters of Twisted Nematic Liquid Crystal Device by Numerical Photometric Ellipsometer

A novel numerical photometric ellipsometer (NPE) under the condition of normal incidence and using a single wavelength laser beam is proposed wherein a continuously rotated quarter wave plate (QWP) at constant speed is required. To precisely measure the cell parameters of a twisted nematic liquid crystal device (TNLCD), the calibration of the QWP is necessary before measurement in this method. All five cell parameters of the TNLCD, namely, twisted angle, cell gap, rubbing angle, pretilt angle, and phase retardation, are obtained by least-square fitting of the measurement data versus the rotation angle of the QWP with the calculated intensity ratio of p- and s-polarization components according to our previously developed theory. The NPE can be extended to the two-dimensional distributions of all five cell parameters by using charge-coupled device (CCD) cameras. Experimentally, the results demonstrate the ability of the NPE to characterize the five cell parameters of the TNLCD in two dimensions with high accuracy and good repeatability.

Full-field characterization of a twisted nematic liquid-crystal device using equivalence theorem of a unitary optical system

Based on the equivalence theorem of a unitary optical system, we proposed an analytical approach to characterize the cell parameters of a twisted nematic liquid-crystal device (TNLCD) with full-field resolution. The spatial distribution of three characteristic parameters of a TNLCD was measured by using a polarizer-sample-analyzer imaging polarimeter so that the untwisted phase retardation, cell thickness, and twisted angle of a TNLCD can be directly calculated through the explicit expressions as a function of the characteristic parameters. The measured results agree well with the given values. This method can be implemented for characterization of a TNLCD in the manufacturing process.

Construction and Electro-Optic Properties of Liquid-Crystal Display Doped by Rhodium Nanoparticles

We prepared 4'-pentylbiphenyl-4-carbonitrile (5CB)-stabilized rhodium (5CB-Rh) nanoparticles and poly(cyclodextrin) (PCyD)-stabilized rhodium (PCyD-Rh) nanoparticles. The average diameter of Rh nanoparticles stabilized by 5CB, PalphaCyD, PbetaCyD, and PgammaCyD are 1.2, 5.4, 6.8, and 5.2 nm, respectively. The nanoparticles were dispersed in liquid crystal 5CB to construct novel twisted nematic liquid crystal device (TN-LCD). Voltage holding ratio was measured for TN-LCD fabricated by doping PbetaCyD-Rh nanoparticles. The decrement of the voltage was very much reduced for that doped with PbetaCyD-Rh. The response time of this TN-LCD in the presence of PbetaCyD-Rh nanoparticles was faster than that in the absence.

Optimized Stokes polarimeters based on a single twisted nematic liquid-crystal device for the minimization of noise propagation

This work evidences the suitability of applying a single twisted nematic liquid-crystal (TN-LC) device to obtain dynamic polarimeters with high accuracy and repeatability. Different Stokes polarimeter setups based on a TN-LC device are optimized, leading to the minimization of the noise propagated from intensity measurements to the Stokes vector calculations. To this aim, we revise the influence of working out of normal incidence and of performing a double pass of the light beam through the LC device. In addition, because transmissive TN-LC devices act as elliptical retarders, an extra study is performed. It analyzes the influence of projecting the light exiting from the TN-LC device over elliptical states of polarization. Finally, diverse optimized polarimeters are experimentally implemented and validated by measuring different states of partially and fully polarized light. The analysis is conducted both for monochromatic (He-Ne laser) and LED light sources, proving the potential of polarimeters based on a single TN-LC device.

Cell parameter measurement of a twisted nematic liquid crystal device using interferometric polarimeter under normal incidence

Five cell parameters of a twisted nematic liquid crystal device (TNLCD), namely, cell gap, pretilt angle, twisted angle, rubbing angle, and phase retardation are precisely measured by the developed amplitude-sensitive heterodyne polarimeter (ASHP) simultaneously integrated with Yeh and Gu's transfer matrix and Lien's transfer matrix. This proposed method can characterize the five cell parameters under the arrangement of a single wavelength at normal incidence. In contrast to the conventional methods on cell parameter detection either by adopting a multiple wavelength laser beam at normal incidence or by using a single wavelength laser beam under oblique incident to TNLCD, this method presents the advantage of not only having a simple setup but also the possibility to measure simultaneously five cell parameters on the characterization of TNLCD at high speed.

Methods to Obtain High-Contrast-Ratio Twisted Nematic Liquid Crystal Device at Wavelength of 1.55 µm

A very high contrast ratio 90° twisted nematic (TN) liquid crystal device at a wavelength of 1.55 µm is a very useful optical component in fiber optical interconnections, but it is not easy to obtain. In this paper the reasons for some difficulties in achieving a high contrast ratio are explained and a practical way to fabricate a high contrast ratio TN cell is provided. Using this method we fabricated many TN cells at a wavelength of 1.55 µm and achieved a contrast ratio higher than 40 dB.

PC04 横電界駆動TNモードの電気光学特性(ディスプレイ)

PC04 横電界駆動TNモードの電気光学特性(ディスプレイ)

Color modulation properties of a liquid-crystal device

The color modulation properties of a twisted-nematic liquid-crystal device are studied based on the Jones calculus. The usefulness of Jones calculus is demonstrated for the blue mode of a supertwisted birefringent liquid-crystal device, after which some experimental results of the color modulation effect for a twisted-nematic liquid-crystal television are presented. We investigated the color dependence of the transmitted light on the applied voltage by using a chromaticity diagram. Most of the experimental results are well explained by the theory derived from the Jones calculus.