Planar Nematic Liquid Crystal Cells Research Articles

Observation of self-starting phase-conjugate oscillation in a planar nematic liquid-crystal cell

We report the observation of self-starting optical phase-conjugate oscillation in a nematic liquid-crystal cell. A theoretical model based on the continuum theory of liquid crystals and optical theory of degenerate four-wave mixing is developed to explain the observed phenomena.

Influence of gamma radiation on the electrooptic behavior of planar nematic liquid crystal cells

We irradiated planar nematic liquid crystal cells with gamma-rays, to study the radiation hardness of their electrooptic characteristics. From the evolution of the electrooptic retardance curve with irradiation dose, we estimated the change of the characteristic liquid crystal material parameters with dose, using a nonlinear least square fitting algorithm. The overall gamma radiation hardness of the device is satisfactory up to doses of 456 kGy (H/sub 2/O). Two effects, however, influence the operation of liquid crystal cells as voltage tunable retarders. Radiation affects first the cohesion of the liquid crystal molecules at the boundaries and second, the conductivity of the liquid crystal cells.

Stationary Optical Noise in Planar Nematic Liquid Crystals Near the Fréedericksz Transition

Abstract We measure, under stationary conditions, the power spectrum of the transmitted and scattered light intensity in a planar nematic liquid crystal cell as a function of the applied voltage in the neighbourhood of the electrically-induced splay Freedericksz transition. The Freedericksz threshold is independently determined using a standard interferometric technique. The low-frequency noise spectral density of the transmitted light displays a well defined peak at the critical voltage; this feature is instead hidden in the scattering noise. We critically examine the performances of these different experimental techniques and show that noise measurements are an adequate tool to study orientation transitions in nematic liquid crystals.

Magnetic Freedericksz Transitions of Nematics with Nonideal Initial Orientations

It is well known, that planar nematic liquid crystal cells with tilted director on the boundaries have no threshold field for magnetic Freedericksz transition. However, it is found that if one arranges the two glass plates of the cell such that the tilt angle of the director on one plate is opposite to that on the other, the same threshold magnetic field as in a cell with ideal initial orientation will be observed. It is found also that for a wedge-shaped cell with ideal initial orientation the threshold field will be lower than that for a planar cell.