Single-crystal lithium niobate has been used as a holographic storage medium. The material undergoes a change in refractive indices upon exposure to suitably intense light thus allowing it to act as a pure-phase, volume-holographic medium requiring no processing. The holograms formed have high diffraction efficiencies and are thermally erasable. The high resolution obtained suggests that such material may be useful in high-capacity, changeable optical information storage, processing and display devices.

The theory of Rayleigh scattering from density fluctuations is applied to data taken in glycerol and n-butanol over wide temperature ranges. It is shown that Brillouin scattering is useful in evaluating the viscoelastic parameters of a liquid when all corrections are properly applied. The position, half-width, and intensity of the Brillouin lines as well as the total intensity are the main features of the spectrum used. The definition of the Landau-Placzek ratio was generalized to be applicable to relaxing liquids and glasses and its behavior was studied over a 200°C temperature range in glycerol. The hypersonic data indicate that at high temperatures (∼70°C) in glycerol the distribution of relaxation times is narrower than that ultrasonically found at lower temperatures (∼−10°C). This result is in agreement with the concept that the origin of the distribution is related to cooperative behavior which is less pronounced at higher temperatures.

No abstract

Experiments have been performed in which 1000 holograms have been superimposed one upon the other in the same area of photographic emulsion. Each hologram was formed with a uniquely coded reference beam allowing reconstruction of only one of the superimposed holograms while the unaddressed holograms contribute incoherent noise. Signal-to-noise ratios are calculated and measured as a function of the number of superimposed exposures. For the 1000-exposure hologram, the observed signal-to-noise ratio for any one of the individual holograms was 10 dB.