V. V. Presnyakov

Interference quenching of light transmitted through a monolayer film of polymer-dispersed nematic liquid crystal

A theoretical study of light transmission through a polymer with a monolayer ensemble of bipolar nematic droplets under applied electric film is performed. The possibility of interference quenching of monochromatic coherent light directly transmitted through the film is predicted theoretically and realized in the experiment.

Bipolar Nematic Droplets with Rigidly Fixed Poles in the Electric Field

Abstract We have studied theoretically the reorientation process induced by the electric field inside a bipolar nematic droplet with rigidly fixed poles. Computer simulation has revealed the threshold director reorientation only in that part of a droplet, where the LC director is orthogonal to the applied field, and the nonthreshold reorientation in the rest of the droplet volume. A formula has been proposed to estimate the threshold field. The data obtained have allowed us to calculate a PDLC film transmittance in the framework of the anomalous diffraction approach and to interpret the oscillating behavior of the volt-contrast curve observed experimentally.

Characteristics of the process of reorientation of bipolar drops of a nematic with rigidly fixed poles

The director configuration in a bipolar drop of a nematic with rigidly fixed poles is calculated as a function of the electric field directed perpendicular to the symmetry axis of the drop. It is shown that the reorientation of the drop is a dual process: a threshold process in the region where the initial director orientation is orthogonal to the electric field, and a nonthreshold process elsewhere in the drop. A relation for determining the critical field is obtained. Experimental investigations of the characteristics of scattered light for a film of polymer-encapsulated liquid crystals confirm the computational results.

Friedericksz Threshold in Bipolar Nematic Droplets with Rigidly Fixed Poles

Abstract We have studied experimentally a problem of the threshold behavior of Friedericksz transition in bipolar nematic droplets with rigidly fixed poles. The dependence of the light transmission of the PDLC film on the applied voltage has obviously revealed a threshold for the straightforward passing beam, confirming the threshold behavior of reorientation process in a central part of the droplet, which was theoretically predicted in [5]. In agreement with a simulation [5] the dependencies of scattering light intensity versus voltage have showed the nonthreshold behavior. We have checked-up also the interference origin of the oscillations of volt-contrast curves for these PDLC films. A number of oscillations and their amplitude depend on wavelength and films thickness.

High Contrast Light Modulator Based on PDNLC Monolayer

Abstract Interference effects in polymer dispersed nematic liquid crystals (PDNLC) films with monolayer arrangement of the LC droplets are investigated. Transmittance characteristics were measured both in dependence on the collection angle and incidence angle. The method of increasing of contrast of light modulators based on such films is discussed.

Volt-contrast curve anisotropy in planar-oriented PDChLC films

Abstract The structural and electrooptical properties of planar-oriented films of polymer dispersed cholesteric liquid crystals with tangential orientation of molecules at the interface were investigated. It is shown, that in this medium, a great difference is observed between the threshold parameters and the form of both polarized components of the volt-contrast characteristic. This effect is due to the specific features of structural transformations of the elongated cholesteric droplets in the electric field.

Uniaxially Oriented Films of Polymer Dispersed Liquid Crystals: Textures, Optical Properties and Applications

ABSTRACT Overview of authors works on uniaxially oriented films (UOF) of polymer dispersed liquid crystals (PDLC) including nematics, cholesterics and ferroelectric smectics are presented. The interference effects such as the oscillations of volt-contrast curves and the quenching of a light transmitted through the nematic PDLC are described. Exceptional behaviour of polarization efficiency revealed in sheared cholesteric PDLC films alive is discussed. We have found the electro-thermooptical hysteresis in cholesteric PDLC and proposed laser-addressed reverse information recording based on it. Structure, optical, dynamic and temperature properties of UOF PDLC based on ferroelectric smectics are presented. Using this material, a single-polarizer and three different types of polarizer-free light modulators were designed.

Polyfunctional optoelectronic elements based on oriented PDCLC films

It has been found that an intermediate orientational structures were formed in elongated droplets of polymer dispersed cholesteric liquid crystals (PDCLC) under electric field effect. Due to this phenomenon a great anisotropy of the polarized components of volt-contrast curve is observed. Optoelectronic element based on oriented PDCLC film may be used as a modulator of the whole of the light, as a modulator of only one polarized component of the light and as a polarizer.

Chiral Additive Effects on Electrooptical Response and Droplet Structure in Uniaxially Oriented Films of Polymer Dispersed Nematic

Abstract Light transmission and director configurations of the uniaxially oriented ensemble of ellipsoidal chiral nematic droplets dispersed in polymer film have been investigated under applied voltage. Depending on a concentration of the chiral additive three different types of the behaviour of such droplets in an electric field are revealed.

Interference effects in electro-optical cells based on PDNLC monolayer

Electrooptical response of a cell based on monolayer film of polymer dispersed nematic liquid crystal is studied experimentally and theoretically both in light scattering mode and in geometry with crossed polarizers. Interference effects revealing in the light passed straightforward through the cells can be used to develop color filters with the spectral characteristics varied due to an applied voltage.