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3D Optical Storage

Three-dimensional (3D) optical data storage is any form of optical data storage in which information can be recorded and/or read with three-dimensional resolution. The current technology of optical data storage media is two-dimensional (2D). 2D optical discs store data as a series of reflective marks on an internal surface of a disc. In order to increase storage capacity, it is possible for discs to hold two or even more of these data layers, but their number is limited since the addressing laser interacts with every layer that it passes through on the way to and from the addressed layer. These interactions cause noise that limits the technology to approximately 10 layers. 3D optical data storage methods circumvent this issue by using addressing methods where only the specifically addressed voxel (volumetric pixel) interacts substantially with the addressing light. The volumetric nature of the data structure requires that the laser light must travel through other data points before it reaches the point where reading or recording is desired. Therefore, some kind of nonlinearity is involved to ensure that these other data points do not interfere with the addressing of the desired point.
3D optical data storage has the potential to provide terabyte and possibly even petabye-level mass storage on clear discs, in a card format, and theoretically even on a crystal, cube or sphere (Storex Technologies Inc). Data recording and readback are achieved by focusing lasers within the disk. Data recording in a 3D optical storage medium requires that a change take place in the medium upon excitation. This change is generally a photochemical reaction of some sort, although other possibilities exist. The most investigated have been photochromic compounds. If the photochemical change is reversible, then rewritable data storage, at least in principle, is possible.
Although there are many nonlinear optical devices, only multiphoton absorption is capable of injecting into the media...