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Layered Structure for Decreasing Laser Energy for Beam Addressable Memory

IP.com Disclosure Number: IPCOM000079486D
Original Publication Date: 1973-Jul-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 3 page(s) / 37K

Publishing Venue

IBM

Related People

von Gutfeld, RJ: AUTHOR

Abstract

A number of parameters can be optimized in order to increase the efficiency with which information can be written and erased in beam-addressable memories (BAM). It is proposed to (1) decrease the thickness of the active storage medium, so that less total energy is required to raise the temperature of a bit to the glass transition or melt temperatures, and (2) allow the net transmitted beam to make multiple passes through the active medium, thereby utilizing the available optical energy almost twice as efficiently.

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Layered Structure for Decreasing Laser Energy for Beam Addressable Memory

A number of parameters can be optimized in order to increase the efficiency with which information can be written and erased in beam-addressable memories (BAM). It is proposed to (1) decrease the thickness of the active storage medium, so that less total energy is required to raise the temperature of a bit to the glass transition or melt temperatures, and (2) allow the net transmitted beam to make multiple passes through the active medium, thereby utilizing the available optical energy almost twice as efficiently.

A layered structure 1 shown in Fig. 1, is designed so that part of the incident light passes through the storage film 2 and is reflected from the surface of a highly reflecting layer 3, allowing it to pass through film 2 a second time. Here, a thermally insulating transparent film 4 which is evaporated or sputtered, separates storage film 2 from the reflecting layer 3 which is also sputtered or evaporated. Without film 4, rapid thermal conduction to the optically reflecting layer 3 would defeat the advantage afforded by the multiple passage of the light through storage film 2. Although exact dimensions of the structure depend on the wavelength of light used, typically, insulating film 4 should be an odd integral number of quarter-wave lengths of the laser light divided by the index of refraction of the insulating layer 4. Film 4 can be a material such a MYLAR* or KAPTON*.

An alternate scheme for coupling the light more efficiently into the storage medium is possible, based on the following additional considerations:

The highest theoretical temperature attained by the memory material is that for the adiabatic case, that is, one in which there is no substrate material and no thermal spreading of the heat in the material. A further restriction for the adiabatic case is that the thinnest possible film will reach the highest temperature. However, because a substrate is generally requ...