scholarly journals MOLECULAR BIAXIALITY AND THE LOWEST SUPERCOO-LING TEMPERATURE FOR NEMATIC LIQUID CRYSTALS IN ISOTROPIC PHASE

1999 ◽  
Vol 48 (1) ◽  
pp. 31
Author(s):  
ZHANG ZHI-DONG ◽  
LIU XIN-DIAN ◽  
HUANG XI-MIN
Keyword(s):  
Liquid Crystals ◽  
Nematic Liquid Crystals ◽  
Isotropic Phase

Laser Beam Induces Reorientation in Nematic Liquid Crystals

2010 ◽  
Vol 428-429 ◽  
pp. 224-227
Author(s):  
I Min Jiang ◽  
Yu Jen Chen ◽  
Wen Chi Hung ◽  
C.T. Kuo ◽  
D.J. Jang ◽  
...  
Keyword(s):  
Phase Transition ◽  
Liquid Crystals ◽  
Laser Beam ◽  
Nematic Liquid Crystals ◽  
Beam Propagation ◽  
Isotropic Phase ◽  
Optical Alignment ◽  
Optically Induced

Nematic liquid crystals (NLCs) can be easily reoriented by the laser beam at the temperature closed to the nematic–isotropic phase transition (TNI). At the temperature closed to TNI, the propagating mode of laser beam and the optically induced phase transition were explored by using a microscopic conoscope technique. This investigation demonstrates the formation of soliton at particular beam propagation modes. The interaction between nematic liquid crystals and the laser beam with different polarizations showed the nonlinearity in optical alignment.

scholarly journals Competition between local disordering and global ordering fields in nematic liquid crystals

2010 ◽  
Vol 6 ◽  
Author(s):  
Matej Cvetko ◽  
Milan Ambrožič ◽  
Samo Kralj
Keyword(s):  
Liquid Crystals ◽  
Nematic Liquid Crystals ◽  
Anisotropy Field ◽  
Memory Effects ◽  
Isotropic Phase ◽  
Zero Temperature ◽  
Microscopic Approach ◽  
Random Anisotropy ◽  
Orientational Ordering ◽  
2D And 3D

We study the influence of external electric or magnetic field B on orientational ordering of nematic liquid crystals or of other rod-like objects (e.g. nanotubes immersed in a liquid) in the presence of random anisotropy field type of disorder. The Lebwohl–Lasher lattice type of semi-microscopic approach is used at zero temperature. Therefore, results are valid well below the transition into the isotropic phase. We calculate the correlation function of systems as a function of B, concentration p of impurities imposing random anisotropy field disorder, the disorder strength W and system dimensionality (2D and 3D systems). In order to probe memory effects we calculate correlation length ξ for random and homogeneous initial configurations. We determine the crossover fields B c(p) separating roughly the ordered and disordered regime. Memory effects are apparent only in the latter case, i.e. for B < B c. PACS numbers: 47.51.+a, 47.54.-r, 07.05.Tp, 61.30.-v

Collective and Individual Molecular Nonlinear Photonics of Liquid Crystals

2003 ◽  
Vol 12 (02) ◽  
pp. 277-289 ◽  
Author(s):  
I. C. Khoo ◽  
Andres Diaz ◽  
J. Ding ◽  
K. Chen ◽  
Y. Zhang
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Nematic Liquid Crystals ◽  
Isotropic Phase ◽  
Optical Elements ◽  
Fiber Arrays ◽  
Nonlinear Responses ◽  
Upper Limit ◽  
Phase Liquid ◽  
Nonlinear Light Scattering

This review will examine the origins of nonlinear light scattering processes in nematic liquid crystals, and explore various nonlinear photonic processes associated with optically induced director axis reorientation effects. Our theoretical prediction shows that the upper limit of nematic liquid crystal reorientation nonlinearity can be as high as 1000 cm2/W. The supra-nonlinear responses of nematic liquid crystals enable various self-action or electro-optical guiding, mixing, switching and modulation of light with unprecedented low power thresholds. Owing to the broadband birefringence of NLC, we expect to realize optical elements/devices capable of similar multi-functional operations throughout the visible — infrared regime. We also discuss the optical limiting action of isotropic-phase liquid crystal filled nonlinear fiber arrays.

Dielectric Constants and Molecular Structure of Nematic Liquid Crystals

1974 ◽  
Vol 29 (6) ◽  
pp. 905-911 ◽  
Author(s):  
W. H. de Jeu ◽  
Th. W. Lathouwers
Keyword(s):  
Molecular Structure ◽  
Liquid Crystals ◽  
Dielectric Properties ◽  
Nematic Liquid Crystals ◽  
Dielectric Constants ◽  
Isotropic Phase

Measurements are presented of the dielectric constants of some p,p′-n-alyl and n-alkoxy substituted azobenzenes and azoxybenzenes in the nematic and in the isotropic phase. Starting from the dipole-less, p,p′,di-n-alkyl-azobenzenes, a systematic interpretation is given of the influence of the molecular structure on the dielectric properties.

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