ABSTRACT
Three-dimensional optical data storage is demonstrated in an initially homogenous volume by first recording a reflection grating in a holographic photopolymer. This causes the entire volume to be weakly reflecting to a confocal read/write head. Superposition of two or three such gratings with slightly different k-vectors creates a track and layer structure that specialized servo detection optics can use to lock the focus to these deeply-buried tracks. Writing is accomplished by locally modifying the reflectivity of the preexisting hologram. This modification can take the form of ablation, inelastic deformation via heating at the focus, or erasure via linear or two-photon continued polymerization in the previously unexposed fringes of the hologram. Storage by each method is demonstrated with up to eight data layers separated by as little as 12 microns.
Subject(s)
Optical Storage Devices , Optics and Photonics , Computer Storage Devices , Equipment Design , Holography , Lasers , Microscopy, Confocal , Models, Statistical , Photochemistry/methods , Photons , Polymers/chemistry , Reproducibility of ResultsABSTRACT
Polymer films doped with 2-(5, 5-dimethyl-3-styryl-cyclohex-2-enylidene)-malononitrile chromophore and various sensitizers have been prepared and characterized. The material exhibits high sensitivity in the red region (S=0.26 cm(2)/J at lambda=633 nm), a large dynamic range (Dn=-0.05) , and large transient two-beam coupling gain (G=110 cm(-1)) . Self-diffraction effects, such as energy and phase coupling, and photoinduced scattering are studied.
ABSTRACT
The optimization of a real-time holographic interferometer that uses photorefractive Bi(12)SiO(20) crystals as the recording media through anisotropic self-diffraction is considered with regard to the optical noise and sensitivity characteristics of two particular crystals. A simple theoretical treatment is given to describe the factors influencing the maximum area of an object that can be viewed interferometrically by using these crystals. Experimental values of the noise distribution and sensitivity of the crystals are presented and used to obtain a value for the maximum observable object area of the order of 1 m(2).
ABSTRACT
Experimental results are reported for four-wave mixing at 633 nm with a photorefractive Bi(12)TiO(20) crystal in a double phase-conjugate mirror geometry. Recording in the presence of an alternating electric field with optimum focusing of interacting Gaussian beams yields up to 40% diffraction efficiency for the hologram.
