Magnetic Holography and Its Application to Data Storage

The principle of magnetic holograms and its application to holographic memory are reviewed. A magnetic hologram was recorded through a thermomagnetic recording as a difference in magnetization direction and reconstructed with the magneto-optical effect. To achieve a bright reconstruction image, it is important to record deep magnetic fringes on the materials with large Faraday rotation coefficients. This technique was applied to the holographic memory using transparent magnetic garnets as a recording material. The first reconstruction image was dark and noisy, but improvements in the recording conditions resulted in error-free recording and reconstruction of the magnetic hologram. To form deep magnetic fringes, insertion of heat dissipation (HD) layers into recording layer was proposed. It was found that this HD multilayer medium showed diffraction efficiency higher than that of a single layer medium, and error-free recording and reconstruction were also achieved, using magnetic assisted recording. These results suggest that HD multilayer media have potential applications in recording media of magnetic holographic data storage. In future, a high recording density technique, such as multiple recording, should be developed.

Holographic memory and information

Holographic memory and information

Holographic memory updated by contradictory information: influence of low frequency attenuation on response stability

A 6f-scheme of Fourier holography with resonant architecture is considered, which implements memory replenishment with new information that contradicts the previously recorded. It is shown that the low-frequency attenuation due to the nonlinearity of the exposure characteristics of holographic recording media in the initial reference holographic image recorded in a narrow filtering range corresponding to the degradation in the correlation plane of the global maximum of the autocorrelation function below the lateral maxima leads to the response instability — an intermittent mode. It is shown that the intermittent mode corresponds to the restructuring of the autocorrelation function of a composite standard recorded in holograms from one range of values of the approximation model parameters to another. It is shown that the correlation length of the composite image recorded in holograms is an order parameter of the system; its rapid change precedes the loss of response stability and the transition to an unstable regime with intermittency. The results of numerical simulation are presented.