Investigation of a Photodichroic Material for Holographic Storage and Recovery.

摘要

Sodium fluoride (NaF), a face-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 storing and recovering information holographically. The material is capable of write, erase, and read cycling with good reproducibility. The authors have identified a refractive-index shift at the base of the absorption zones, which 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 satisfactorily demonstrated that it is a prime candidate for holographic storage where real-time write, read, and erase are specified requirements. (Author)