Investigation of a Photodichroic Material for Holographic Storage and Recovery.
Annual technical rept. Jul 72-Aug 73,
STANFORD RESEARCH INST MENLO PARK CALIF
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Sodium fluoride NaF, a space-centered cubic alkali halide crystal, when irradiated by high-energy electrons, X-rays, or ions forms F and M center absorption bands that can be modified by illumination with spatially modulated, polarized UV light at room temperature. The dipole moment formed by the M center provides a very-high-resolution polarizable absorption that can be read with polarized light and is therefore capable of information storage and recovery by holographic methods. The material is capable of write, erase, and read cycling with good reproducibility. Determination that there is a refractive-index shift at the base of the absoprtion zones suggests that phase holography is possible in this material, with attendant improved diffraction efficiencies. Modification of color-center formation by selected ion implantation indicates that higher sensitivity and diffraction efficiencies are possible without sacrificing the desirable properties of the basic material. Fourier-transform holograms as well as multiple gratings have been recorded and recovered. This material has satsifactorily demonstrated that it is a prime candidate for holographic storage where real-time write, read, and erase are specified requirements. Author