摘要:

It is shown that it is possible to determine such NLC constants as viscosity, elasticity and thermoconductivity simultaneously by measuring the NLC eigenmode relaxation times using the probing beam diffraction on the refractive index grating excited by short laser pulses. The amplitudes of gratings have been calculated. Optimal conditions for excitation and detection of the gratings have been pointed out.

ISSN:1058-725X    

DOI:10.1080/15421409208048235

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The Optical Fréedericksz Transition is studied in homeotropically aligned nematic E7 doped with cholesteric C15. The transition is found to be first-order and with large hysterisis. A simple model is also proposed.

ISSN:1058-725X    

DOI:10.1080/15421409208048236

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Guided electromagnetic waves (GEW) of optical frequency range in cholesteric liquid crystals (CLC) of finite thickness in conditions of total internal reflection on both boundaries are theoretically examined. Two kinds of interface are discussed: CLC - metal, CLC - dielectric. It's shown that in such films two types of waves can propagate: damped and undamped modes. The main characteristics of GEW of the both types have been investigated in detail, the domains of the existence have been determined. The comparative analysis of GEW and surface waves of semi-infinite samples has been done.

ISSN:1058-725X    

DOI:10.1080/15421409208048237

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Rheo-optical studies on aligned and unaligned melts of a main chain thermotropic polyester with flexible spacers are discussed in terms of the predictions of the Ericksen-Leslie equations. Experiments show that the material exhibits two different shear-flow regimes depending on the temperature at which the experiments are performed. It is shown, using conoscopy, that the director is flow-aligning at temperatures close to TNIand nonflow-aligning close to a smectic to nematic (TSN) phase transition. The implications of these results are discussed in terms of the change in sign of one of the Leslie viscosity coefficients and interpreted in the framework of the Ericksen-Leslie Theory.

ISSN:1058-725X    

DOI:10.1080/15421409208048238

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The anisotropic third-order nonlinear optical susceptibility χ(3)of monodomain samples of nematic solutions of poly[1,4-phenylene-2,6-benzobisthiazole], PBT, a rodlike polymer, have been studied by third harmonic generation. The principal component of χ(3)(−3ω;ω,ω,ω) is not along the nematic director, as opposed to the linear dielectric, which has the maximum refractive index along the director.

ISSN:1058-725X    

DOI:10.1080/15421409208048239

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Optical surface guided electromagnetic waves (SGEW) of the second order diffraction in cholesterics are examined in the framework of dynamical diffraction theory. The dispersion equations are obtained and analyzed. Allowed SGEW frequency band and directions of propagation (relative to the orientation of director at the cholesteric surface) are found. The dependence of SGEW penetration in cholesteric on the frequency and propagation direction is investigated. It is shown that two of the four different SGEW modes of the second diffraction order have unusual polarization properties changing with the SGEW frequency.

ISSN:1058-725X    

DOI:10.1080/15421409208048240

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Refractive index measurements of uniaxial media (crystals and a polymer liquid crystal in the nematic phase) are described. The technique used, applicable for any anisotropic uniaxial medium, makes use of the birefringence to generate interference between the extraordinary and ordinary waves created after an incident plane polarized wave enters the crystal. The dispersion of the refractive indices for the uniaxial nematic polymer is discussed together with the implication it has on the third order nonlinear optic susceptibility measurements completed using the Third Harmonic Generation (THG) technique.

ISSN:1058-725X    

DOI:10.1080/15421409208048241

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The Landau-deGennes theory predicts interesting pretransitional surface behavior at the interface between a liquid crystal and a smooth or rough substrate. In the former case, we propose a simple form for the liquid crystal-substrate interaction which yields enhanced surface ordering in the nematic and a uniaxial-biaxial transition in the isotropic phase. For the experimentally accessible range of liquid crystal-substrate interaction strengths, the experimentally observed pretransitional behavior in the isotropic phase is in excellent agreement with the theory. For the case of a rough substrate, pretransitional surface disordering in the nematic is predicted and measured directly by evanescent-wave ellipsometry, while pretransitional random-planar surface ordering occurs in the isotropic phase.

ISSN:1058-725X    

DOI:10.1080/15421409208048242

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A new alignment technique of small tilted homeotropic alignment using rubbing method (THR method) has advantage in obtaining large area uniformity and productivity because of non-requirement of large vacuum equipment. In this paper, the applicability of this method for display device is discussed.

ISSN:1058-725X    

DOI:10.1080/15421409208048243

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The reorientation of an initially well aligned nematic rodlike solution of the rodlike poly(1,4-phenylene-2,6-benzobisthiazole), PBT, in an external magnetic field in the sample plane is studied. For angle β between the magnetic fieldHand the initial directornless than 45 degrees, the reorientation occurs by a homogeneous twist distortion of the director field, permitting assessment of the Frank elastic constant KTand the Leslie viscosity ηT.For larger β, the reorientation is nonhomogeneous, with a component of the distortion out of the sample plane, resulting in a phase-grating, made manifest by its focusing effects for transmitted light.

ISSN:1058-725X    

DOI:10.1080/15421409208048244

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor