| dc.description.abstract | In this thesis we have shown the virtues and the drawbacks of phase objects and amplitude objects in holographic storage in LiNbO3 crystal with angular
multiplexing . We think that there are two virtues in the use of phase objects: one is the increase of diffraction efficiency, the other is the decrease of bit error rate.
In Chapter 4, we have demonstrated experimentally that the recording of a phase object yields higher diffraction efficiency compared with that yields by
the recording of an amplitude object. It is thought that this result is due to more
gratings are built in the crystal when a phase object is recorded because the
object light from a phase object covers the whole crystal.
For a practical holographic storage system, usually many pages of
information are stored in the crystal. These pages of information are stored in
the crystal in series using multiplexing technique. As a result, the information
stored in the later portion of the recording sequence will erase the preceding
stored information. Accordingly, when the stored information are amplitude
objects, the erasing effect will not be uniform over the whole page because the
intensity of the stored object is not uniform. Therefore, when the stored data are
binary, error bits of information may suffer large change in intensity and become
an error bit after thresholding. In Chapter 3, we aim to discuss this problem and
supply some experimental results to support this point of view. However, the
experimental results are not conclusive and further investigation are needed. | en_US |