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AssigneeCommissariat a l'Energie Atomique
InventorsSalim Mimouni, Fabien Laulagnet
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The invention relates to the writing and optical reading of high-density information. The higher energy density at the center of the reading laser beam is used for modifying the energy structure of an active layer in such a way as to make it capable of bearing surface plasmons. The coupling of the laser beam and the active layer thus modified can then excite surface plasmons in an interface between a dielectric layer and the active layer. These surface plasmons are disturbed by physical marks having very small dimensions and written in the optical storage medium; these disturbances generate a remote-field optical response which can be detected by a detector. The operation is carried out in super-resolution, the surface plasmons being generated only at the center of the laser beam and not at the periphery. It is therefore possible to write and to read again marks having dimensions of size smaller than the theoretical resolution of the optical reading system.
An optical method of reading information written in a high-density storage medium, wherein
An optical storage medium comprising a substrate in which physical marks are formed, the marks being covered by an active layer and by a dielectric layer, the active layer being made of a material having a first possible electronic energy state and a second possible electronic energy state, the layer being capable only in the second state of bearing surface plasmons generated by an illumination by a reading laser beam and the layer being a doped semiconductor layer having an optical index which differs depending from the energy state.
A system for the optical reading of information storage medium comprising a laser source, focusing optics and means of polarization of the focused beam, the power density in a small zone at the center of the focused laser beam being sufficient to cause an active layer of the storage medium to change from its first energy state into the second energy state in such a way as to make it capable of bearing surface plasmons, the polarization means being capable of polarizing the laser beam in TM predominant mode, said active layer being a doped semiconductor layer having an optical index which differs depending from the energy state.
Dependencies are inferred from the claim text.