摘要:

Surface stabilized smectic liquid crystal devices can be used in a wide variety of optical filters for providing very rapid discrete, and continuous tunability. One such example, analyzed here, is the discrete switching Ferroelectric Liquid Crystal Polarization Interference Filter (FLCPIF). This filter is implemented using binary swiching surface stabilized FLC's and linear polarizers. A single-stage FLCPIF is analyzed, and the number of output spectra is determined which optimizes performance and makes the most efficient use of the devices. The extension of principles to multiple-stage FLCPIF's, and FLCPIF's which include passive retarders is discussed.

ISSN:1058-725X    

DOI:10.1080/15421409208048245

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The orientation of the smectic-A and -C* layers, inside 25 μm pores of glass capillary arrays, has been studied by high-resolution x-ray diffraction. The pores were coated with lecithin in order to ensure perpendicular anchoring of molecules at the surface. A chevron-like layer structure was seen in the smectic-A phase of 8CB, while a uniform structure was found in the smectic-C* phase of, both, ZLI-3041 and CBC.

ISSN:1058-725X    

DOI:10.1080/15421409208048246

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Different susceptibility expansions for the polarization densityPare compared to identify cascading contributions to the nonlinear response of a medium. In certain liquids pair-correlation dependence of the nonlinear optical susceptibilities has been observed. To isolate the cascading effects that depend most sensitively on pair correlation and near-field effects, a simple statistical model forPis applied to the case of a liquid whose oriented molecules have only first hyperpolarizabilities; then all third-order effects inPare a consequence of cascading.

ISSN:1058-725X    

DOI:10.1080/15421409208048247

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Generally when anisotropic material such as liquid crystals are confined in a Fabry-Perot cavity, the transmission through the device becomes sensitive to the input polarization. While continuous tunability of the refractive index is possible by applying a small electric field across the liquid crystal, It is found that under certain circumstances a forbidden gap in transmission wavelength is observed. It is shown that this occurs because of mode mixing brought by slightly twisted uniaxial structure disposed between the Fabry-Perot structure. A theoretical model is presented to explain the experimentally observed data with excellent agreement.

ISSN:1058-725X    

DOI:10.1080/15421409208048248

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

We succeeded in storing optical information with low-molecular-weight cholesteric liquid crystals. Nematic mixtures of glassy compounds which are chiralized by the addition of small amounts CB15 (BDH) have been used. Reversible optically induced holographic gratings were stored both below the glass transition temperature and above the glass transition in the temperature region of high viscosity. Erasure can be achieved by local heating of the sample making possible to use the material for multiple storage processes. A mechanism to explain the formation of the grating is discussed.

ISSN:1058-725X    

DOI:10.1080/15421409208048249

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

We report the time behavior of nonlinear light diffraction driven by a square wave voltage in samples of polymer dispersed liquid crystals. The short peak (2–3 ms) in the leading edge of the signal is shown to be due to the occurrence of a transient amplitude grating in the sample. This effect is explained by the measured dependence of the transmittivity on the light intensity, reported here for the first time. A simple theoretical model gives a satisfactory account of the experiental observations.

ISSN:1058-725X    

DOI:10.1080/15421409208048250

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The first non-calamitic/disc-shaped metal organyl series3and6containing two or even four palladium atoms and eight or twelve flexible side chains presented here have been synthesized via the novel roof-shaped/bent dimers2or (the thermomesomorphic)5, respectively. In addition, from the chemical point of view the dodecaethers5and6a-care the first derivatives of four novel, uniquely structured tetrapallado-macroheterocycles. Whereas the type of mesophase of5is still not distinctly clear yet those ones of6a-care enantiotropicdiscotic hexagonal columnar(Dh) over a wide range of temperature. On the other hand, the dinuclear palladocompounds3a-drepresent the first (monotropic) cases of metallomesogens exhibiting thenematic-discotic(ND) phase. This thermotropic nematic type of phase clearly gets stabilized by doping3c, dwith a strong electron acceptor; under such circumstances mesophase conversions/inductions (ND→Dh) are observed in the cases of3a-c.Finally, it is important to emphasize that the very large, thermotropically Dhphase displaying macroheterocycles6a-care alsolyotropicin various organic solvents exhibiting now anematicphase.

ISSN:1058-725X    

DOI:10.1080/15421409208048251

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Recently, a surface induced transition from homeotropic to planar alignment in a nematic layer and the corresponding optical response has been reported/K. Flatischler, L. Komitov, S. T. Lagerwall, B. Stebler, and A. Strigazzi, Mol. Cryst. Liq. Cryst.,198, 119 (1991)/. In the case of surface conditions with reverse pretilt a similar transition from quasi-homeotropic bent alignment to quasi-planar splayed state can be obtained. As known, these two states are topologically incompatible, and therefore the transition is accompanied by nucleation of π-disclination lines, and even is reversible, it exhibits a big hysteresis. Moreover, it can be driven not only by temperature but also by an applied electric field, using a nematic with negative dielectric anisotropy. A simple theoretical description of such an alignment transition is presented.

ISSN:1058-725X    

DOI:10.1080/15421409208048252

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

In this paper, we present a new kind of bistable liquid crystal display (Filled Nematic) using static light scattering, and its application as a high resolution laser-addressed display. The new material consists of small inorganic particles dispersed in a nematic liquid crystal. In dispersion the particles form internal interfaces with a large specific surface making it possible to stabilize different director configurations. We report the key parameters for reversible optical data storage in this medium and give a first explanation of the physical mechanism of the laser-writing process.

ISSN:1058-725X    

DOI:10.1080/15421409208048253

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Optical power limiting has been observed in glass capillary arrays filled with liquid crystals. This behavior is attributed to optical field induced director reorientation and thermal effects. Dielectric measurements have been carried out to understand the director configurations and director reorientations of the liquid crystals in these near cylindrical glass microcapillaries. Different laser pulse durations from a CW Ar+laser and glass capillary arrays with different pore sizes have also been used in the optical power limiting measurements. Possible mechanisms are discussed and the relative contributions of different mechanisms are assessed.

ISSN:1058-725X    

DOI:10.1080/15421409208048254

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor