Microholographic data storage at the optical resolution limit

In this paper, we report on recording and readout of submicron-sized volume gratings using diffraction limited laser beams. The transversal extent of a micrograting corresponds to the optical resolution limit. The track spacing and bit-to-bit separation are about 500 nm. Arrays of microgratings are recorded through the depth of a photopolymer sample located at different depth positions. The interlayer spacing is less than 8 micron. This way a 3D structure is realized that even refines the surface data structure of current DVDs.