Hughes Electronics Corporation

University of Southern California

Barry A Wechsler

Marvin B Klein

Jack L Feinberg

Stuart MacCormack

Gerald D Bacher

Robert N Schwartz

A new photorefractive material comprises BaTiO.sub.3 double-doped with two dopant species, both of which have at least two valence states, with one of the dopant species (e.g., cerium) having an ionization level that is near the middle of the barium titanate bandgap and the other dopant species (e.g., rhodium) having an ionization level that is closer to the valence band edge of barium titanate, such that both dopant species are sensitive to visible light, but only one dopant species (the one closer to the valence band edge) is sensitive to infrared radiation. The double-doped BaTiO.sub.3 provides a unique combination of photorefractive properties, thereby improving its performance as a holographic storage medium. The double-doped barium titanate crystal is employed as a holographic recording element. The double-doped barium titanate crystal has a dark storage time at room temperature of several years or more and may be nondestructively read out at an infrared wavelength. Recording information on the double-doped barium titanate crystal is done by first sensitizing the double-doped barium titanate crystal with a substantially uniform beam of radiation at one wavelength and then either simultaneously or subsequently storing information in the barium titanate crystal with an incident recording beam that has a wavelength that is longer than that of the sensitizing beam. Nondestructive read-out is accomplished using only the second (writing) beam.

Double-doped BaTiO.sub.3 crystal for holographic storage

An optical amplification system directs a diffraction-limited signal beam through a series of crossings, at substantially less than 90.degree. crossing angles, with a number of non-diffraction-limited pump beams in a photorefractive medium. The pump beams are e-polarized while the signal beam travels down the crystal medium's c-axis and is polarized in the same plane as the pump beam polarization, resulting in an energy transfer from the pumps to the signal beam while leaving the signal beam diffraction-limited. The photorefractive medium is preferably a series of BaTiO.sub.3 :Rh crystals that are aligned parallel to the angled edge of a wedged-shape prism through which the pump beams are transmitted, with the crystals cut so that their C-axes are parallel to the signal beam.

Optical amplification system with non-orthogonal signal and distributed

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Newbury Park, CA, United States of America

Barry A Wechsler