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A multistable spatial optical device has been developed on the basis of a spatial light modulator which contains photosensitive and electrooptical liquid crystal layers where an internal feedback loop is established.

A bistable spatial optical device has been developed on the basis of a spatial light modulator which contains photosensitive and electrooptical liquid crystal layers, where an internal feedback loop is established.

An experimental study was made of photosensitive metal-insulator-semiconductor structures in contact with a nematic liquid crystal. Utilization of the orientational electrooptic effect in the liquid crystal ensured a high energy sensitivity of a structure with gallium arsenide as the semiconductor. Modulation of the phase of light by π or attainment of the highest optical contrast (of the order of 100:1) was achieved when the minimum intensity of the exciting helium-neon laser radiation (λ=633 nm) was 5×10–7 W/cm2 and the switching energy was 10–8–10–9J/cm2. Spatial resolution was at least 10–12 lines/mm. A structure of this kind could be used for coupling in and conversion of optical data, including visualization of infrared radiation.

An increase in the efficiency of light emission (by over an order of magnitude) was achieved for plasma oscillations in a thin silver film of a gold–aluminum oxide–silver (Au–Al2O3–Ag) structure by altering the permittivity of a nematic liquid crystal adjoining the silver film.

A system for holographic page-organized recording of data with the aid of a time-dependent phase-modulated object beam was proposed and tested. Transformation of the initial amplitude image into one modulated in phase was performed in a liquid-crystal spatial light modulator. This system made it possible to relax requirements in respect of the homogeneity of a number of properties of the modulator and in respect of the precision of its fabrication.

The analysis of current-voltage characteristics for channel models of MHD devices gives reason to believe that, in specific cases, the uniformly distributed discharge at the cathode is "stripped" and that an eIectric arc appears [1]. It has also been surmised [2] that a "unidirectional" are exists, which penetrates the boundary layer and extends on one side into the cathode glow and on the other side into the uniform current in the body of the plasma stream. These phenomena have been observed both on "cold" [2], and hot electrodes made of silicized graphite [1]. In order to verify these assumptions, a series of experiments was performed on a channel model to detect arc discharges. The work was carried out in a stream of air (T G ~ 3000 ~ K) with an applied electric field (UEF F = 80 V, f = 50 Hz); the temperature range of the operating surface of the electrode T w was from 1200 to 2000 ~ C, and the additive content varied from 0 to 1.2% by weight of the flow rate. The channel mode1 and the measurement circuit are described in [1]. Together withthe usual oscillograms for the current-voltage characteristics (electrode-electrode and electrode-probe types), the experiments also gave the corresponding values of current and voltage displayed on a time scale. Fig. 1 gives a typical current-voltage electrode-probe characteristic for an electrode made of silicized graphite; Fig. 2 gives an oscillogram of the current and voltage displayed on a time scale. The section OD of the electrode-probe oscillogram (Fig. 1) (the potential drop in a gas layer of thickness ~5 mm as a function of the current flowing in the electrode circuit) corresponds to an operating regime in which the electrode under investigation acts as an anode, and the segment OABC corresponds to an operating regime where this electrode acts as a cathode. We see from Figs. 1 and 2, that the arcs are struck at a specific breakdown voltage U~', corresponding to the point B, after which the voltage decreases and the current increases. While the arc is burning, the voltage remains practically constant during one-half period or decreases a little (point C). After the voltage reaches a value corresponding to the point A, the conditions necessary for maintaining an arc regime disappear and the electrode again begins to operate in a distributed discharge regime. Here, as in the initial sector OB, a sinusoidal variation of current and voltage in the electrode circuit is observed. The oscillograms obtained for the variation of voltage and current in the electrode circuit of a channel model for a MHD device correspond in shape to the voltage and current oscillograms of the stabilized arc between the electrodes of a variable current plasmatron. 9 Fig. I