US Patent 7781042 - Optical storage using nanoparticles

http://ip.com/patent/US7781042

Optical disk memory conventionally involves etching pits into a media surface which are read by a laser. The deposition of metal nanoparticles has been proposed as a higher resolution alternative to etching pits and this patent from Thomson Licensing teaches a multilayer nanoparticle optical disk memory which may provide still higher density storage. Claim 1 reads:  

1. Optical storage medium having

at least a first storage layer with nanoparticles and a second storage layer with nanoparticles,

each storage layer being made of a dielectric material,

wherein the dielectric material of the first storage layer has a different dielectric permittivity than the dielectric material of the second storage layer.