Accession Number : ADP008241

Title :   Holography in Frequency Selective Media: Hologram Phase and Causality,

Corporate Author : EIDGENOESSISCHE TECHNISCHE HOCHSCHULE ZURICH (SWITZERLAND)

Personal Author(s) : Bernet, Stefan ; Kohler, Bern ; Rebane, Alexander ; Renn, Alois ; Wild, Urs P.

Report Date : 22 MAY 1992

Pagination or Media Count : 4

Abstract : Persistent spectral hole burning in conjunction with holography (PSHB) opens new prospects for high density optical information storage and processing. In the holographic approach, hole burning is carried out with two-crossed coherent laser beams which bleach out a narrow frequency domain hole in an inhomogeneously broadened absorption band recording, at the same time, a spatial holographic fringe pattern. During read out of the hologram diffraction from this spatial fringe pattern occurs, and a holographic image is reconstructed, reflecting the changes of the absorption coefficient and the refractive index introduced by the spectral hole. The variation of the refractive index as a function of the frequency extends further than the corresponding absorption coefficient change. If many holograms are recorded at adjacent frequencies, the refractive index gratings cause interference between the holographic signals recorded at different frequencies. A possible way to avoid interaction, and to suppress the buildup of a spectrally non-selective background signal, is to control the relative phase of the holograms. It has been shown, that relative phase changes of pi between adjacent holograms in the frequency domain as well as in the electric field dimension result in a considerable reduction of this background. In this case, however, the holograms stored at different frequencies should have similar spatial structure and contrast.

Descriptors :   *HOLOGRAPHY, *OPTICAL STORAGE, *MOLECULAR SPECTROSCOPY, ABSORPTION, ABSORPTION COEFFICIENTS, DENSITY, DIFFRACTION, ELECTRIC FIELDS, FREQUENCY, FREQUENCY DOMAIN, HIGH DENSITY, HOLOGRAMS, IMAGES, INTERACTIONS, INTERFERENCE, LASER BEAMS, LASERS, PATTERNS, PHASE, PROCESSING, REFRACTIVE INDEX, SIGNALS, TIME, OPTICAL IMAGES, REFRACTIVE INDEX, THIN FILMS, CRYOSTATS.

Subject Categories : Holography
      Atomic and Molecular Physics and Spectroscopy

Distribution Statement : APPROVED FOR PUBLIC RELEASE