Three-dimensional patterned media for ultrahigh-density optical memory

We report a recording medium in which a three-dimensional nanoscale structure can be photofabricated for multilayered optical memory using a two-photon process. By fabricating the structures in the medium, we can control the shape of recorded bits and, in effect, their spatial frequency distribution. We succeeded in recording bits with a 0.5μm interval in any particular plane and 2.0μm interval between successive layers. Thus, storage density of 2.0Tbits∕cm3 is achieved.