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The excitation of rhythmic current oscillations in a diode cell containing a nematic liquid crystal is studied. The external
electric field in the interelectrode gap is directed parallel to the surfaces which orient the liquid crystal molecules. The
current oscillations are accompanied by the formation of an autosoliton at the cathode, which propagates and disappears at
the anode. A hypothetical model is proposed to explain this current instability.
Zh. Tekh. Fiz. 68, 125–127 (January 1998) 相似文献
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We show how to simulate the equatorial section of the Schwarzschild metric through a flowing liquid crystal in its nematic
phase. Inside a liquid crystal in the nematic phase, a traveling light ray feels an effective metric, whose properties are
linked to perpendicular and parallel refractive indexes, n
o
and n
e
respectively, of the rod-like molecule of the liquid crystal. As these indexes depend on the scalar order parameter of the
liquid crystal, the Beris-Edwards hydrodynamic theory is used to connect the order parameter with the velocity of a liquid
crystal flow at each point. This way we calculate a radial velocity profile that simulates the equatorial section of the Schwarzschild
metric, in the region outside of Schwarzschild’s radius, in the nematic phase of the liquid crystal. In our model, the higher
flow velocity can be on the order of some meters per second. 相似文献
5.
A. M. Parshin V. A. Gunyakov V. Ya. Zyryanov V. F. Shabanov 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(8):1045-1048
The change in the domain texture of the 5CB nematic liquid crystal on the surface of a polyvinyl butyral gelatinous polymer
solution cured in a magnetic field is studied optically. The alignment of the nematic is described by the effective order
parameter S* of the polydomain cells. The anchoring energy of a liquid crystal with gelatinous polymer W
ϕ = 1 × 10−3 erg/cm2 is determined. 相似文献
6.
I. Gvozdovskyy K. Shcherbin D. R. Evans G. Cook 《Applied physics. B, Lasers and optics》2011,104(4):883-886
Refractive index grating recording is achieved in the infrared in a nematic liquid crystal placed between semiconductor CdTe
substrates. Light-induced space-charge field created in photorefractive semiconductor substrates varies an alignment of liquid
crystal molecules inhomogeneously in space forming a spatial modulation of the refractive index in liquid crystal. Two-beam
coupling is studied in the hybrid cell, in which a gain factor Γ=16 cm−1 is achieved in the layer of liquid crystal of the sandwich. 相似文献
7.
R. S. Akopyan R. B. Alaverdyan S. Ts. Nersisyan É. A. Santrosyan Yu. S. Chilingaryan 《Technical Physics》1999,44(4):462-463
A thermomechanical flow of uniformly oriented nematic liquid crystal induced by a quasistatic electric field is observed.
This flow occurs when the electric field strength exceeds the static Fréedericksz transition threshold. The effect is attributed
to an electric-field-induced nonuniformity of the director orientation which is required for the onset of the thermomechanical
effect. The experimental results show good agreement with the theoretical estimates.
Zh. Tekh. Fiz. 69, 122–124 (April 1999) 相似文献
8.
Summary The structures of the interface between an isotropic liquid and a nematic liquid crystal and also between different uniaxial
nematic phases are studied. It is shown that, at a planar orientation in the case of the nematic-isotropic liquid interface
and also at a mutually orthogonal orientation of the director in the case of two nematic phases, the interface has the structure
of a biaxial nematic liquid crystal.
Work presented at the second USSR-Italy Bilateral Meeting on Liquid Crystals held in Moscow, September 15–21, 1988. 相似文献
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M. I. Barnik A. S. Zolot’ko V. F. Kitaeva 《Journal of Experimental and Theoretical Physics》1997,84(6):1122-1130
The interaction of linearly and circularly polarized beams with a nematic liquid crystal doped with light-absorbing dyes has
been studied by light-diffraction and microprojection methods. It has been found that there is a threshold for the emergence
of light-induced anisotropic structures, which, depending on the type of dye, can be axisymmetric or extended in a direction
determined by the light field. Possible mechanisms leading to the formation of the anisotropic structures are discussed.
Zh. éksp. Teor. Fiz. 111, 2059–2073 (June 1997) 相似文献
11.
V. A. Loiko U. Maschke V. Ya. Zyryanov A. V. Konkolovich A. A. Miskevich 《Optics and Spectroscopy》2011,110(1):110-118
We considered light scattering by a polydisperse ensemble of droplets of a nematic liquid crystal. To model light scattering
by a monolayer of polymer-dispersed spherical droplets of a nematic liquid crystal with cylindrical symmetry of its internal
structure, we proposed a semianalytical modeling method. The method is based on interference approximation of the theory of
multiple wave scattering, anomalous diffraction approximation, and effective-medium approximation. The method takes into account
cooperative optical effects in concentrated, partially ordered layers and can be used to analyze the small-angle structure
of the intensity of scattered radiation in relation to the concentration, size, polydispersity of liquid crystal droplets,
orientation of their optical axes, and refractive indices of the liquid crystal and polymer. The obtained relations can be
applied to solving direct and inverse problems of light scattering in composite liquid crystal materials using data of polarization
measurements. We present graphical results of solving the direct problem for components of the polarization vector of scattered
wave. These results illustrate the formation of an angular structure for monolayers with a high concentration of polydisperse
droplets of the liquid crystal in the range of small scattering angles (0 < θ
s
≤ 8°). 相似文献
12.
The electric field-induced orientational transition in a homeotropically oriented nematic liquid crystal cell is investigated.
The interaction with the field as a result of anisotropy of the permittivity and flexoelectric polarization is taken into
account. For an arbitrary energy of interaction of the nematic with the substrate simple relations are derived for determining
the threshold characteristics of the phase transition. It is shown that, in contrast with planar orientation, in fields above
a critical value a periodic structure can occur only by virtue of the flexoelectric effect. The resulting dependences for
the threshold parameters in the given geometry are exceptionally useful for determining experimentally the surface energy
and the difference in the flexoelectric coefficients.
Zh. éksp. Teor. Fiz. 116, 543–550 (August 1999) 相似文献
13.
The formation of regular colloid patterns in free-standing smectic films at the transition from the smectic-C to the isotropic
or nematic phase is well known experimentally. The self-organization of isotropic or nematic droplets is caused by their mutual
interaction, mediated by elastic distortions of the local director in the surrounding liquid crystal. These distortions are
related to the anchoring conditions of the director at the droplet border. We describe analytically the energetics of the
liquid crystal environment of a single droplet in one-constant approximation. A method of complex analysis, Conformal Mapping,
is employed. Following a suggestion of Dolganov et al. (Phys. Rev. E. 73, 041706 (2006)), energetics of chain and grid patterns built from the colloids are investigated numerically in order to explain
experimentally observed formations and their director fields. 相似文献
14.
D. Andrienko Yu. Kurioz Yu. Reznikov V. Reshetnyak 《Journal of Experimental and Theoretical Physics》1997,85(6):1119-1124
Surface driven reorientation effects in a nematic liquid crystal cell caused by light-induced changes of the anchoring parameters
were studied. Theoretical consideration of one-dimensional flat distributions of the director has shown that the director
can undergo threshold reorientation between hybrid, homeotropic, and planar alignments as the anchoring energy varies continuously.
The threshold reorientation takes place when the reference and light-induced easy axes are perpendicular. In the one-elastic-constant
approximation the light-induced transition was found to be of second order as shown by a critical increase of the director
thermal fluctuations in the vicinity of the transition point. These effects were experimentally studied in the cells containing
5CB liquid crystal aligned by the photosensitive azo-containing polymer layer.
Zh. éksp. Teor. Fiz. 112, 2045–2055 (December 1997)
Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor. 相似文献
15.
ABSTRACTThis study investigates the optical resonance spectra of free-standing monolithic single crystal silicon microspheres immersed in various amorphous fluids, such as air, water, ethylene glycol, and 4-Cyano-4’-pentylbiphenyl nematic liquid crystal. For the various amorphous fluids, morphology-dependent resonances with quality factors on the order of 105 are observed at 1428 nm. The mode spacing is always on the order of 0.23 nm. The immersion in various amorphous fluids affects the spectral response of the silicon microsphere and heralds this technique for use in novel optofluidics applications. Even though the nematic liquid crystal is a highly birefringent, scattering, and high-index optical medium, morphology-dependent resonances with quality factors on the order of 105 are observed at 1300 nm in the elastic scattering spectra of the silicon microsphere, realizing a liquid-crystal-on-silicon geometry. The relative refractive index and the size parameter of the silicon microsphere are the parameters that affect the resonance structure. The more 4-Cyano-4’-pentylbiphenyl interacting with the silicon microsphere, the lower the quality factor of the resonances is. The more 4-Cyano-4’-pentylbiphenyl is interacting with the silicon microsphere, the lower the mode spacing Δλ of the resonances is. The silicon microspheres wetted with nematic liquid crystal can be used for optically addressed liquid-crystal-on-silicon displays, light valve applications, or reconfigurable optical networks. 相似文献
16.
The dispersion and anisotropy of the permittivity of the liquid crystal 5CB in the solid, nematic, and isotropic phases are
investigated at frequencies ranging from 50 to 1000 MHz using discretely tunable hybrid microstrip cavities. Resonance features
which grow with increasing temperature are observed in the dielectric spectra. It is found that the section of the dispersion
which is due to oriented vibrations of the mesophase molecules covers the frequency range almost up to 300 MHz, and the resonances
found could be due to conformational vibrations of the molecules.
Pis’ma Zh. éksp. Teor. Fiz. 66, No. 4, 251–253 (25 August 1997) 相似文献
17.
Molecular orientations and photorefractive effects of C60-doped nematic liquid crystals were investigated with layer-structured liquid crystal cells where a nematic phase was injected.
Regardless of the surface treatments of the layers, liquid crystals injected with nematic phase showed a higher degree of
director orientation and photorefractivity than those injected with an isotropic phase. The nematic alignment of liquid crystals
in an untreated cell is generated by a capillary flow of liquid crystal during the nematic injection. However, it was observed
that the grating formation was delayed a little longer with injection of nematic phase than with injection of isotropic phase.
Received: 11 March 2002 / Revised version: 22 April 2002 / Published online: 12 July 2002 相似文献
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K. Kowiorski J. Kędzierski Z. Raszewski O. Chojnowska K. Garbat 《Phase Transitions》2016,89(4):403-410
ABSTRACTWedge cells of small apex angle, filled with liquid crystals, were used to determining optical characteristics as functions of temperature for three liquid crystalline mixtures recently produced and a reference nematic. The interference fringes appearing in polarised monochromatic light (of sodium yellow line) normally incident on the cell were exploited to measure the ordinary and extraordinary refractive indices in the reflection mode and birefringence in the transmission mode. The measurements were repeated using Abbe's refractometer for 6CHBT as the reference to verifying the precision. Additionally the order parameter was computed from birefringence as a function of temperature. The results confirm the usefulness of the method and provide the properties of two nematic liquid crystals of small and large birefringence and one smectic liquid crystal of medium birefringence, recently produced. The experimental systems served also to investigating phase transition between the liquid crystals and the isotropic liquid at near-clearing temperature. 相似文献
20.
ABSTRACTThe method of widening of the blue phase (BP) temperature range is presented. By means of polarising optical microscopy, we demonstrate that the temperature regime in which BP is stable is greatly enhanced by the cell thickness changes in mixtures of nematic liquid crystal (LC) and chiral dopant. 相似文献