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Erasable optical memory and method
| Details |
Inventors: Efron, Uzi; Wu, Chiung-Sheng; Dalton, Larry Raymond; Wiener-Avnear, Eli;
Assignee: Hughes Electronics Corporation (El Segundo, CA)
Primary Examiner: Tucker; Philip
Assistant Examiner:
Attorney, Agent or Firm: Duraiswamy; V. D., Denson-Low; W. K.
An erasable optical memory is provided by an erasable bistable photoactive chromophore that is covalently bonded to a polymer microsphere. An azobenzene chromophore that is bonded to the microsphere by an oxygen or NH replacement of chlorine, or a CH double bond to N, is preferred. An array of such microspheres is encoded by applying radiation at a resonant wavelength to induce a conformational change in the chromophores for selected microspheres, and the encoded pattern is read out by detecting changes in either absorption or fluorescence. |
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DETAILED DESCRIPTION The present invention seeks to provide a novel optical memory system, and associated fabrication and operating methods, that has a high memory density and data coding speed, low levels of noise and cross-talk and an ambient temperature operation, and yet is erasable so that its coding pattern can be changed.
These goals are achieved by covalently bonding erasable bistable photoactive chromophores to respective polymer microspheres.
Rather than chemically decomposing when illuminated at its microsphere's resonant wavelength, the chromophore undergoes a change of state that changes its fluorescence and/or absorption characteristics, but can be restored to its original response state by illumination at an erase wavelength.
An array of such microspheres with slightly different diameters can be provided as in prior MDR systems to form a spatial array with a rapid writing and readout capability.
However, the use of an erasable chromophore with a covalent bond to the underlying microsphere avoids a chemical decomposition of the chromophore during resonance, and allows it to be restored to its original state by illumination at an erase wavelength.
For even higher memory density the microspheres can be provided in a 3-D array of microsphere layers, with the microspheres at each depth in the array sized different from the microspheres at other depths.
In a preferred embodiment the chromophore comprises an azobenzene, preferably azobenzene amphiphile.
The surface of the polymer microsphere, which is preferably polystyrene, is functionalized with a hydroxyl group that provides an oxygen replacement for chlorine in the azobenzene, or with an amine group that provides an NH replacement for chlorine in the azobenzene.
Activated chromophores are detected either by detecting changes in their fluorescence, or in their absorption characteristics.
These and other features and advantages of the invention will be apparent to those skilled in the art from the following detailed description, taken together with the accompanying drawings
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Semiconductor manufacture 
