Static information storage and retrieval – Radiant energy – Color centers
Patent
1987-01-30
1989-03-07
Hecker, Stuart N.
Static information storage and retrieval
Radiant energy
Color centers
372 42, G11C 1142
Patent
active
048112895
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an optical recording device, and, more particularly, to an optical recording device which includes a doped crystal structure for optically storing bits of information through the use of light.
BACKGROUND OF THE INVENTION
The need for the storage and retrieval of information in modern society is increasing at a rapid rate. In most computer-based information systems, bits of information are conventionally stored in magnetic memories. For example, magnetic tape and disc storage systems are in prevalent use with many types of computer systems ranging from main frame computers to home computers. In a magnetic memory, bits of information are magnetically stored or recorded on a magnetic recording medium.
Recently, optical storage and retrieval systems have been considered and proposed as alternatives or, at least, as supplements to the conventional magnetic storage systems. In conventional optical storage systems, bits of information are stored in various types of recording mediums and the bits of information are readable by light through different mechanisms, such as changes in rreflectivity or polarization.
In accordance with the present invention, an optical storage device is provided which optically stores bits of information. The optical storage device in accordance with the present invention is extremely effective and has a wide range of applicability in optical storage and retrieval systems. Optical storage devices in accordance with the present invention may be designed to provide an erasable memory having a relatively fast switching time for recording and erasing bits of information.
SUMMARY OF THE INVENTION
In accordance with the present invention, an optical recording device is provided for the optical storage and retrieval of bits of information. The optical recording device includes a crystal selected from the group of alkali metal halides and alkali-earth halides. The crystal is doped with an alkali metal dopant and negative hydride ions to form a doped crystal having a hydride light absorption band centered about a particular frequency and a color center light absorption band centered about another particular frequency.
The crystal is sufficiently doped with the alkali metal dopant and the negative hydride ions to exhibit two switching states. The first state has a predetermined light absorption level in the hydride band a low light absorption level in the color center band and the second state has a predetermined light absortion level in the hydride band and a high light absorption level in the color center band. The doped crystal is repeatably switchable between the first and second states by the irradiation of switching light onto the doped crystal. The irradiation of switching light of a selected intensity for a predetermined time period in the hydride band switches the state of the doped crystal from the first state to the second state. Similarly, the irradiation of switching light of a selected intensity for a predetermined time period in the color center band switches the state of the doped crystal from the second state back to the first state.
The doped crystal provides a non-volatile optical memory for bits of information by exhibiting one or the other state until such state is switched by the irradiation of the appropriate switching light. Since the doped crystal switchably exhibits two states, the doped crystal erasably stores bits of information. The state of the doped crystal is readable, for example, by measuring the transmission of a read light through the crystal in the respective first and second states, the read light having an intensity insufficient to switch the state of the doped crystal.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing summary, as well as the following detailed description of the preferred embodiments of the present invention, will be better understood when read in conjunction with the accompanying drawings, in which:
FIG. 1 is a diagrammatic view of an optical recording system employing an opti
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patent: 4091375 (1978-05-01), Robillard
patent: 4490016 (1984-12-01), Schneider et al.
patent: 4649518 (1987-03-01), Sadjian
IBM Tech. Discl. Bull., vol. 11, No. 10, Mar. 1969, p. 1259, "Optical Memory Using Self-Trapped Holes in a Solid" by Dreyfus Radio & Electronic Engineer, vol. 40, No. 1, Jul. 1970, pp. 17-25, Colour Centres by Taylor, et al.
Applied Physics, vol. 25, No. 2, Jun. 1981, pp. 87-90, "Thin Film Aggregate Color Centers", by Ortiz et al.
"Color Centers in Solids" by Schulman et al., U.S. Naval Research Laboratory, pp. 112-138, published 1962.
pp. 28-30 of Proceedings of a Physical Society by R. W. Pohl, (London), vol. 40 E3 (1937).
pp. 89-91 from Review of Modern Physics, vol. 26, No. 1, Jan., 1954.
pp. 109-110 of book, "Physics of Color Centers", edited by W. Beall Fowler, Academic Press, New York and London (1968).
Garcia Alfonso
Hecker Stuart N.
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