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Optical Memory Using Self Trapped Holes in a Solid

IP.com Disclosure Number: IPCOM000090234D
Original Publication Date: 1969-Mar-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 26K

Publishing Venue

IBM

Related People

Dreyfus, RW: AUTHOR

Abstract

Cubic crystals, as well as crystals of lower symmetry, can be made to display dichroism by having color centers which are aligned along a specific axis. The color centers must have an identifiable axis, i.e., observable dichroic properties, and be capable of reorienting. Reorientation is induced by the absorption of optical energy by the color center. Random orientations can be obtained by heating the crystal. Since the color centers have two or more identifiable orientations and a stable orientation in the dark at sufficiently low temperature, color centers can store information in alkali-halide crystals as well as other crystal systems.

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Optical Memory Using Self Trapped Holes in a Solid

Cubic crystals, as well as crystals of lower symmetry, can be made to display dichroism by having color centers which are aligned along a specific axis. The color centers must have an identifiable axis, i.e., observable dichroic properties, and be capable of reorienting. Reorientation is induced by the absorption of optical energy by the color center. Random orientations can be obtained by heating the crystal. Since the color centers have two or more identifiable orientations and a stable orientation in the dark at sufficiently low temperature, color centers can store information in alkali-halide crystals as well as other crystal systems.

Self-trapped holes have advantages for the storage of information. The self- trapped hole in KCl, potassium chloride, has an identifiable axis because the hole overlaps two C1/-/ ions on neighboring sites. In KCl, the neighboring sites lie on one of the six <110> axes. The self-trapped hole is oriented to lie along a particular >110| axis by radiation with polarized light of 3650 Angstroms or 7500 Angstroms wavelength. The production and reorientation of self-trapped holes usually take place near liquid nitrogen temperature, i.e., -196 degrees C. The specific orientations remain fixed in the dark as long as the temperature stays below -100 degrees C. An advantage of the self-trapped hole is that no thermal energy is required for efficient reorientation of the centers, i.e., th...