Fluorescence images approaching sub-micron resolution are formed in thin nanocrystalline phosphor films. The images are created with UV exposure of the films under chrome-coated quartz masks. The UV light locally changes the valence state of the samarium ions in the nanocrystalline phosphors to activate fluorescence properties. The red fluorescence images are then read-out with blue-violet light. With an imaging resolution approaching the diffraction limit, this technology has potential for anti-counterfeiting labelling or optical data storage applications.
In this paper, a novel and efficient approach to digital optical data storage using rare-earth ion doped inorganic insulators is demonstrated. More specifically, the nanocrystalline alkaline earth halide BaFCl:Sm is shown to hold great potential for multilevel optical data storage. Proof-of-concept demonstrations show that these phosphors could be used for rewritable, multilevel optical data storage down to the physical dimensions of a single nanocrystal. Multilevel information storage is based on the highly-efficient and reversible conversion of Sm3+ to Sm2+ ions upon exposure to UV-C light. The stored information is efficiently read-out by employing the photoluminescence of the Sm 2+ ions in the nanocrystals, with the signal strength being dependent on the UV-C intensity used during the write step. This serves as the mechanism for multilevel data storage in the individual nanocrystals. This data storage platform has the potential to be extended to 2D and 3D memory for storage densities that could approach tera- or even petabyte/cm3 levels.