Roger R. Dube

Theory of complementary holograms arising from electron–hole transport in photorefractive media

The time evolution of space-charge field gratings in photorefractive media is derived for a simple two-level electron–hole-transport model. At one level, charge transfer occurs by electron transport, and at the other, by hole transport, thus leading to the formation of complementary gratings. If the characteristic lifetimes of the gratings differ significantly, extended-lifetime gratings are possible. The role of the applied electric field in the evolution of such gratings is examined, and limiting cases are considered. The results of the derivation are compared with examples of complementary gratings in the literature.

Hardware-based Computer Security Techniques to Defeat Hackers: From Biometrics to Quantum Cryptography

The protection of critical information and systems is a major component of todays electronic business community. This valuable reference presents the primary hardware-based computer security approaches in an easy-to-read toolbox format. The techniques discussed show readers how to perform their own evaluation of new and emerging security technologies. It is an invaluable source for computer engineers, computer security specialists, electrical engineers, software engineers, IT professionals, and advanced undergraduate and graduate students in computer engineering and computer science.

The Photorefractive Effect In Doped Bismuth Silicon Oxide Crystals

Bismuth silicon oxide is one of the most sensitive photorefractive materials available today. It is therefore important to develop an understanding of how its photorefractive properties can be altered by adding impurities during growth. In this paper results from analyses of doped bismuth silicon oxide crystals grown by the addition of impurities to the melt during Czochralski growth are presented, and the influence of these impurities and their concentrations on the photorefractive effect are determined. Doped crystals are used in a holographic arrangement, and the effects of dopants and temperature on grating formation (erasure time and diffraction efficiency) are reported. Data on the effect of dopants on long-term retention time are also presented. The apparent effects of certain impurities on traps are reviewed. The results are discussed and compared with current models.