Hughes Aircraft Company

Sanat K Sashital

Anthony L Gentile

Robert L Joyce

Disclosed is a multilayer electro-optical material having a plurality of adjacent, single crystals wherein each crystal layer has different electrical and optical properties from its adjacent layer or layers. This material is made by a method wherein the successive layers are epitaxially grown from a molten solution of said electro-optical material optionally containing at least one dopant. In one embodiment, such electro-optic material comprises silver thiogallate, wherein successive epitaxial layers are grown from a molten solution of silver thiogallate and potassium chloride, and which optionally includes at least one dopant. This molten solution exhibits the characteristic that, for any specific solution composition, layers having different electrical and optical properties can be obtained by cooling over the temperature range which will yield crystal growth of the composition corresponding to the desired electrical and optical properties. By taking advantage of this temperature/composition phase precipitation, multi-layers are formed by cooling first within one temperature range to form on the seed crystal substrate a layer of silver thiogallate including the dopant and then subsequently forming on this first layer a second layer of different composition varying from substantially pure silver thiogallate to silver thiogallate including at least one dopant, by cooling within a different temperature range. By successively alternating between cooling over these different temperature ranges, multiple layers are formed with adjacent layers having different electrical and optical properties. The multi-layerd structures produced by the above method can be utilized in electro-optical devices, and particularly as the tunable birefringent medium in tunable electro-optic filters.

Doped and undoped single crystal multilayered structures

A method of making a thin, high purity single crystal layer of silver thiogallate. According to the preferred embodiment of this method, a seed crystal substrate of silver thiogallate is dipped into a molten solution of silver thiogallate dissolved in potassium chloride. Upon slowly cooling the solution, the thin layer of single crystal silver thiogallate forms on the substrate. Upon removal, very little of the potassium chloride adheres to the surface, and what does adhere to the surface can be easily removed by washing the surface with hot water.

Silver thiogallate single crystal layers epitaxially grown from

A method of growing a single crystal layer of silver thiogallate having a maximum thickness of 50 micrometers. This crystal is of a high purity having a higher degree of crystalline perfection than the substrate on which it is grown. The crystal is grown epitaxially from a solution of silver thiogallate in a solvent of either antimony sulfide or lead sulfide. The solution is prepared by heating a mixture of the materials (solid silver thiogallate in molten solvent) slowly at a rate of, for example, 3.degree. to 5.degree. C. per minute until the mixture reaches a temperature about 10.degree. C. above the liquidus, and maintaining this temperature for 16 hours or more. The above referenced solution is then gradually cooled at a rate of, for example, 1.degree. C. per minute to the temperature at which crystal growth is to be initiated. At this temperature a polished single crystal substrate of a material which has an appropriate lattice relationship with silver thiogallate is dipped into the molten solution. The solution and substrate are then cooled at a slow rate of, for example, 0.05.degree. C. per minute over the temperature range within which crystal growth is to occur. During this cooling, the substrate is rotated in the melt. On obtaining the desired thickness of the epitaxially-grown single crystal layer, the substrate is withdrawn from the solution.

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Thousand Oaks, CA, United States of America

Sanat K Sashital