Self-organized ensembles of nematic domains in magnetic and electric fields.

The structural and magneto- and electro-optical properties of a self-organized ensemble of nematic domains formed on a polycarbonate film in the presence of a residual solvent are studied. The film covered one of the plane-parallel glass plates of a liquid crystal cell. The magnetic field stabilizing the planar alignment of the liquid crystal was applied parallel to the cell surfaces and the reorienting electric field, perpendicular to them.

Eigenmodes in a photonic structure with a torsion-deformed nematic liquid crystal exposed to a magnetic field.

The polarized components of transmission spectrum of a multilayered photonic structure containing a nematic liquid crystal under the magnetic-field-induced torsion deformation have been investigated. Since the planarly twisted director structure of the nematic is unrelated to a decrease in its optical anisotropy, the control of the polarization and spectral characteristics of the eigenmodes is based on the occurrence of a geometric phase, whose contribution gradually increases upon nematic deformation. Along with the previously observed blue shift of the cavity o modes, the anomalous shift of the cavity e modes to the long-wavelength region (red shift) of the transmission spectrum has been detected.

Alignment of liquid crystals by polymers with residual amounts of solvents.

The homogeneous nematic layers in liquid crystal cells with treated surfaces are affected by orientational transitions in the electric, magnetic, or temperature fields. The liquid crystal structures formed on solid or liquid surfaces find limited application in identifying the liquid-crystal states by the textures observed in polarized light. The use of surfaces prepared from polymer solutions makes it possible to significantly broaden the range of application of the liquid crystal structures.

Electric and magnetic field-assisted orientational transitions in the ensembles of domains in a nematic liquid crystal on the polymer surface.

Using electro- and magneto-optical techniques, we investigated orientational transitions in the ensembles of domains in a nematic liquid crystal on the polycarbonate film surface under the conditions of competing surface forces that favor radial and uniform planar alignment of nematic molecules. Having analyzed field dependences of the intensity of light passed through a sample, we established the threshold character of the orientational effects, plotted the calculated intensity versus magnetic coherence length, and compared the latter with the equilibrium length that characterizes the balance of forces on the polymer surface.

Domain structures in nematic liquid crystals on a polycarbonate surface.

Alignment of nematic liquid crystals on polycarbonate films obtained with the use of solvents with different solvations is studied. Domain structures occurring during the growth on the polymer surface against the background of the initial thread-like or schlieren texture are demonstrated. It is established by optical methods that the domains are stable formations visualizing the polymer surface structures.

Magnetic-field tunable defect modes in a photonic-crystal/liquid-crystal cell.

Light transmission spectrum of a multilayer photonic crystal with a central liquid-crystal defect layer placed between crossed polarizers has been studied. Transmittance was varied due to the magnetically induced reorientation of the nematic director from homeotropic to planar alignment. Two notable effects were observed for this scheme: the spectral shift of defect modes corresponding to the extraordinary light wave and its superposition with the ordinary one.