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Optical Memory

IP.com Disclosure Number: IPCOM000079521D
Original Publication Date: 1973-Jul-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 3 page(s) / 32K

Publishing Venue

IBM

Related People

Chaudhari, P: AUTHOR [+2]

Abstract

A three-dimensional optical memory using materials switchable from an amorphous state to a crystalline state and back again to its amorphous state, is operated by focusing a laser beam into different depths of the material. The material, when in its crystalline state, is capable of generating the harmonic of the frequency of the incident light used to interrogate its state, whereas in its amorphous state it is not a generator of harmonics. The detection of this harmonic allows for increased discrimination in the data-reading process.

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Optical Memory

A three-dimensional optical memory using materials switchable from an amorphous state to a crystalline state and back again to its amorphous state, is operated by focusing a laser beam into different depths of the material. The material, when in its crystalline state, is capable of generating the harmonic of the frequency of the incident light used to interrogate its state, whereas in its amorphous state it is not a generator of harmonics. The detection of this harmonic allows for increased discrimination in the data-reading process.

The diagram shows such a memory in which a laser beam is used for writing information into a storage medium. A suitable source comprises a laser 2 capable of being tuned to generate different frequencies, or could consist of two adjacently located lasers wherein each is capable of generating a laser beam at a desired frequency. The laser 2 is held by a support 4, which can be positioned to direct focal points of energy to different positions within the three-dimensional volume of storage medium 6. Interposed between laser 2 and medium 6 is a light deflector 8 and a focusing lens L. Writing takes place in different planes P of the medium 6, by converting a spot of material from an amorphous to a crystalline state. Each spot of material has a diameter of the order of wavelength of the laser beam and the spacing between the planes P is the order of several wavelengths. Terminals T1 and T2 receive electrical pulses for actuating light deflector 8.

Materials preferred for medium 6 are amorphous chalcogenide semiconductor materials, e.g., Te(85)Ge(11)As(4).

The laser should be tuned to have an output frequency near the absor...