This paper describes the fundamentals of phase-only liquid crystal on silicon (LCOS) technology, which have not been previously discussed in detail. This technology is widely utilized in high efficiency applications for real-time holography and diffractive optics. The paper begins with a brief introduction on the developmental trajectory of phase-only LCOS technology, followed by the correct selection of liquid crystal (LC) materials and corresponding electro-optic effects in such devices. Attention is focused on the essential requirements of the physical aspects of the LC layer as well as the indispensable parameters for the response time of the device. Furthermore, the basic functionalities embedded in the complementary metal oxide semiconductor (CMOS) silicon backplane for phase-only LCOS devices are illustrated, including two typical addressing schemes. Finally, the application of phase-only LCOS devices in real-time holography will be introduced in association with the use of cutting-edge computer-generated holograms. The capabilities and applications of phase-only liquid crystal on silicon (LCOS) technology are reviewed by scientists in China and the United Kingdom. Zichen Zhang and co-workers from Tsinghua University in Beijing and the University of Cambridge describe how an electronically controlled liquid-crystal pixel array on a silicon backplane can be useful for manipulating the phase of coherent light. Such LCOS phase modulators have many potential applications, including real-time holography, head-up displays, wavelength-selective switches and reconfigurable optical add-drop multiplexers. Commercial devices currently offer array sizes of up to about 1-inch diagonal with pixel pitches in the range 6–20 μm. However, the technology is still immature; the liquid-crystal materials and silicon control backplane need to be optimized in order to realize the potential of such devices.

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Fundamentals of phase-only liquid crystal on silicon (LCOS) devices

We have studied the important n-cyano biphenyl series of mesogens, n=4-8 using modelling and molecular dynamics simulations. We have been able to obtain spontaneously ordered nematics upon cooling isotropic samples of 250 molecules. We show that, using the united atom force field developed here, the experimental isotropic–nematic transition temperatures are reproduced within 4 K, allowing a molecular level interpretation of the odd–even effect along the series. Other properties, like densities, orientational order parameters and NMR residual dipolar couplings are also well reproduced, demonstrating the feasibility of predictive in silico modelling of nematics from the molecular structure.

Towards in silico liquid crystals. Realistic transition temperatures and physical properties for n-cyanobiphenyls via molecular dynamics simulations.

The present invention provides a liquid-crystal display panel with which it is possible to alleviate an occurrence of display misalignment and a degradation of contrast when using a color filter of four or more colors. This liquid-crystal display panel comprises a color filter substrate further comprising four or more color layers and a shutter layer, wherein a repeating unit of the four or more color layers is treated as one pixel. The four or more color layers respectively overrun a portion of the shutter layer. The liquid-crystal display panel includes regions wherein color layers of the same color which are included in different pixels, respectively, are arranged in either the same rows or the same columns. Of the four or more color layers which configure the one pixel, the overrun width with respect to the shutter layer whereon a color layer with a color with greater brightness is positioned between the color layers of the same color is narrower than the overrun width with respect to the shutter layer whereon a color layer of a color with lesser brightness is positioned between the color layers of the same color.

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Liquid crystal display panel

High tilted antiferroelectric liquid crystalline materials

The synthesis and properties of a few dozen highly evolved analogues of (S)-MHPOBC are reported The liquid crystal phases, and phase transition temperatures and enthalpies, as evidenced by polarized optical microscopy and differential scanning calorimetry, respectively, are given The helical pitch in pure compounds and some mixtures is estimated using the selective reflection method All of the compounds show antiferroelectric phases, and some key structure–property relationships for the new materials are reported Specifically, it is found that the length of the oligomethylene segment of a novel partially fluorinated alkoxy ether tail incorporated into the structures strongly influences the stability of the antiferroelectric phase and the observed phase sequences, as well as the values of the helical pitch and its temperature dependence The formulation of a family of broad temperature range eutectic mixtures possessing the highly desirable orthoconic antiferroelectric phases with long helical pitch is described

Influence of alkoxy chain length and fluorosubstitution on mesogenic and spectral properties of high tilted antiferroelectric esters

The birefringence and refractive indices of several liquid crystalline structures were measured throughout the visible wavelength region (400–900 nm) at different temperatures. Mixtures composed of members of the same homologous series were used in order to achieve the nematic phase at room temperature. Data on 28 mixtures, mainly with cyclohexane - phenyl and biphenyl cores, are presented. The set includes widely used structures as well as newly synthesized. Some details of experimental methods, formulas for interpolation of the results and observed regularities are briefly discussed.

Birefringence and Refractive Indices Dispersion of Different Liquid Crystalline Structures

The invention relates to an essentially pressure-insensitive liquid crystal cell. Electrode-equipped (5, 6) plates (1, 2) are arranged at a predetermined distance from each other and define a liquid crystal layer of a thickness d. At least a first (1) of the plates is transparent and has a thickness b not exceeding 1 mm, and a modulus of elasticity E. Spacers (11) fixed in the cavity and having a height h are distributed with a spacing L and have substantially the same modulus of elasticity E as said first plate. The spacers (11) have a width not exceeding 50 νm, at least in one direction. The degree of surface coverage s by the supporting areas of the spacers (11) on said first plate (1) exceeds or is equal to a minimum value which is dependent on the type of liquid crystal. L is so selected in dependence on current values of d and b that, when applying a pressure P on the first plate (1), a maximum relative deflection Δd/d, caused by the pressure P, of said first plate between the spacers satisfies condition (A): Δd/d=PL4/4Eb3d≤G, where G is equal to the value of expression (B), representing a relative compression of the spacers caused by the same pressure P, for a case where the degree of surface coverage s assumes the above-mentioned minimum value (B): Δh/h=P/sE.

Pressure-insensitive liquid crystal cell

We present the results of molecular dynamics simulation studies of 4-(trans-4'-pentylcyclohexyl)- benzonitrile (PCH5) at different temperatures in the isotropic and nematic phases within the united atom approach. Special attention is paid to the electrostatic interactions. Different methods of determining point charges are compared and the effect of the electrostatic interactions on the molecular distribution is considered. Their decisive influence on local molecular packing and phase transition temperature is shown. We analyse various static and dynamic properties, being specially interested in the reliability of the simulation results, to check to which extent they are distorted by the confinements adopted during the simulations (and especially the size of the system). Using realistic molecular interaction models in contrast to simple model ellipsoids, we find that the number of molecules and the lengths of the simulation runs have to be increased considerably when studying macroscopic properties like t...

Temperature dependence of the properties of simulated PCH5

Chiral (S) 4-(1-methylheptyloxycarbonyl)phenyl 4′-(ω-trifluoroethoxyalcoxy)biphenyl-4-carboxylates and 4′-(ω-trifluoro-butanoyloxyalcoxybiphenyl)carboxylates were prepared and their phase transitions and the temperature dependence of the smectic layer spacings, tilt angle, spontaneous polarization, threshold and switching times for the antiferroelecrtic—ferroelectric transition were measured.

Antiferroelectric Compounds with trifluoromethyl group in ω-Position of Terminal Chain

We demonstrate a quarter wave phase retarder consisting of two layers of different liquid crystals (LCs). The phase retardation does not differ by more than ±5% from the target value π/2 within a spectral interval of 200 nm in the visible range. These values are comparable to the data for commercial two layer crystalline retarders which are much more expensive, especially if large apertures are required. In order to design the LC retarder we measured the birefringence of the LC within the entire visible spectrum using a published technique which does not consider interference effects due to reflections within indium-tin oxide coated LC cells. We show that these effects do not affect the results adversely provided that the birefringence data are taken over a broad spectral range.

Sergei Ye. Yakovenko

Papers

Birefringence and Refractive Indices Dispersion of Different Liquid Crystalline Structures

Pressure-insensitive liquid crystal cell

Temperature dependence of the properties of simulated PCH5

Antiferroelectric Compounds with trifluoromethyl group in ω-Position of Terminal Chain

Birefringence measurements of liquid crystals and an application: An achromatic waveplate