Patent ID: 7742208

Claim:
A rewriteable diffraction grating, comprising: a first layer; a second layer adjacent to the first layer, the first and second layers defining a boundary between the first and second layers; a plurality of first nanoparticles, wherein each first nanoparticle is configured and arranged to selectively generate one or more charge carriers in response to a write beam; and a plurality of second nanoparticles, wherein the second nanoparticles are different in composition from the first nanoparticles and each second nanoparticle is configured and arranged to substantially alter its opacity to light from a read beam upon receiving one or more charge carriers from the first nanoparticles and thereby form a light diffraction pattern, with regions that are substantially transparent to the read beam and regions that are substantially opaque to the read beam, in response to a diffraction pattern written on the plurality of first nanoparticles by the write beam; wherein the plurality of second nanoparticles are disposed in proximity to the plurality of first nanoparticles to permit charge carriers generated by the first nanoparticles to be transferred to the second nanoparticles and to selectively interact with the second nanoparticles; and wherein the second nanoparticles are configured and arranged for erasing the light diffraction pattern by releasing one or more charge carriers in response to illumination of the second nanoparticles with an erase beam; wherein the first nanoparticles are primarily disposed in the first layer and the second nanoparticles are primarily disposed in the second layer, wherein a portion of the first nanoparticles are diffused into the second layer across the boundary between the first and second layers and a portion of the second nanoparticles are diffused into the first layer across the boundary between the first and second layers.