We demonstrate a polarization-invariant liquid-crystal (LC) grating in an oppositely twisted and mutually orthogonal configuration. The polarization-invariant LC grating with high diffraction efficiency is fabricated using a single-masking process with two-step exposure of a linearly polarized ultraviolet light. It is found that the zeroth- and the first-order diffracted beams are linearly polarized and perpendicular to each other irrespective of the incident polarization for the phase retardation of m pi (m=integer).
We report on a new tranflective liquid crystal display (LCD) mode having a single cell gap and a single LC mode. For this display mode, a low twisted nematic liquid crystal cell, having the twist angle of 60 , is used for both transmissive and reflective applications. The measured electro-optic characteristics of our transflective cell agree well with numerical simulation results. It is found that the transmittance and the reflectance become identical to each other in the high voltage regime. The new transflective configuration is useful for mobile LCD applications.
Eigh impedance electric probes and symmetric and unsymmeiric floating double probes have been used to measure electric field, potential, density and temperature in a plasma stream. The plasma is fully ionized, supersonic and collisionfree. It moves in a magnetic field, where the electron gyro radii are of the same order as the probe radii, and where the ion gyro radii are large (n, N 1018 m-3, tr N 3 . 105 m/s, To 31 10 eV, B N 0.02 Vs/m2).Some aspects of basic theory are briefly discussed and it is shown that reliable measurements can be obtained under certain conditions.
We report on a linearly graded phase model for the design of binary diffraction gratings of liquid crystals (LCs) associated with the periodic interfacial effect. The binary nature of the LC grating is produced by use of periodic striped domains in an alternating homeotropic and hybrid geometry. In our graded phase model the diffraction patterns and the diffracted intensities of the LC binary grating is primarily governed by three length scales: the cell thickness and two distortion parameters scaled by the grating period at two domain boundaries. The experimental data agree well with theoretical predictions made in our linearly graded phase model as well as the elastic continuum theory.
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