The maximum storage density of a volume-type hologram memory obtainable with a prescribed signal-to-noise ratio is discussed. In the theoretical analysis, a microscopic particle model of a phase hologram is considered; the refractive index variation is assumed to be caused by the density variation of bleached silver particles distributed spatially at random. The signal and noise intensities are derived from the analysis based upon this model. The theoretical limit of the storage density and the optimum hologram thickness are then derived in terms of the signal-to-noise ratio. The maximum storage density is finally given as a function of the average scattering cross section of the particles, the light wavelength, and the prescribed signal-to-noise ratio. Some practical cases are also discussed on the basis of measured material parameters.
A single electron transistor (SET) with floating gate, which has a non-volatile memory effect, is successfully integrated with MOS circuits. By applying high voltage generated by the charge pump circuit to the floating gate SET, the characteristics control of Coulomb blockade oscillation is demonstrated for the first time at room temperature. This attempt will open a new path of adding new functionality to conventional MOS circuits by integration with so-called Beyond CMOS devices.
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