IEEE Computer Volume 11 Number 9 -- New Applications
Original Publication Date: 1978-Sep-01
Included in the Prior Art Database: 2005-Nov-10
Software Patent Institute
D. A. Michalopoulos: AUTHOR [+3]
New Applications * New computer storage method based on laser photochemistry
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Prof. D. A. Michalopoulos
California State University, Fullerton edited by
Prof. D. A. Michalopoulos California State University, Fullerton
New computer storage method based on laser photochemistry
A new approach to storing data in computers, using a tunable dye laser, is described in US Patent 4,101,976 awarded to scientists at IBM's San Jose Research Laboratory.
Based on a photochemical process called "hole burning," the new system provides a unique method for increasing the amount of information that can be packed into a given space.
In the system, each bit of data is identified by its location in the frequency spectrum as well as by its location in two- or three-dimensional space. Potentially, many hundreds or even thousands of the frequency-coded bits could be stored at a single, microscopically small region in space. The size of these regions could be as small as the diffraction limit of a laser beam, a dimension of the order of one micrometer /1/25,000 of an inch).
The invention depends on the use of a laser that can be tuned so that it emits light of various colors, but whose light rays at a particular setting of the dial all oscillate within an extremely narrow frequency band.
The highly monochromatic light from such a laser is directed onto a photoreactive material. This produces a chemical change in a very small percentage of the material's molecules -- just those whose spatial orientation enables them to absorb energy at the frequency of the laser light.
As a result of the chemical reaction, the frequency-selected molecules are changed into a new compound, and none of the original molecules are left to absorb light at the frequency that produced the reaction. The phenomenon is observed as the forming of a gap, or "hole," in one of the material's optical absorption peaks -- hence, the name, "hole burning."
These absorption peaks can be thought of as features in a graphical "fingerprint" that distinguishes one material from another. They occur when the light waves
cause certain atoms to absorb part of the radiation and vibrate in concert with it. The effect is conceptually similar to the resonant vibrations of a tuning fork.
In testing the feasibility of the holeburning technique for data...