Patent ID: 8243574
Filing Date: 2012-08-14
Classification: G11B

Abstract:
1. An optical method of reading information written in a high-density storage medium, wherein the information written in the storage medium is covered by an active layer having a first possible electronic energy state and a second possible electronic energy state, the active layer being capable only in the second electronic energy state of bearing surface plasmons generated by an illumination by a reading laser beam, this active layer being covered by a transparent dielectric layer, said active layer being a doped semiconductor layer having a first complex optical index in the first electronic energy state which differs from a second complex optical index in the second electronic energy state, the method comprising: a. producing a laser beam; b. focusing the laser beam on the active layer; c. polarizing the focused beam; d. wherein the power density in a small zone at the center of the focused laser beam is sufficient to cause the active layer to change from the first electronic energy state into the second electronic energy state in such a way as to make it capable of bearing surface plasmons; e. wherein a real part n and an imaginary part k of the complex optical index n+ik in the second electronic energy state being such that k f. wherein the polarization provides the laser beam with a TM predominant polarization mode.