Holography in Frequency Selective Media: Hologram Phase and Causality,
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.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 22, 1992
- Accession Number
- ADP008241
Entities
People
- Alexander Rebane
- Alois Renn
- Bern Kohler
- Stefan Bernet
- Urs P. Wild