Accuwave Corporation

California Institute of Technology

Victor Leyva

George A Rakuljic

Amnon Yariv

Koichi Sayano

Charles E Tyler

Sze-Keung Kwong

Arthur Bruce O'Connor

Harold Everett Miller, Jr

Xiaoping Mao

Substantial improvements in photorefractive device lifetimes are provided by control of electron migration which results in the decay of gratings in photorefractive materials due to diffusion and other effects. A new class of photorefractive devices using compensating electronic and ionic gratings having relatively low efficiency but nonetheless usable gratings is provided by arranging the gratings to be reflective in a wavelength band outside the photo-excitation band of the photorefractive material, as by using an infrared operating wavelength. Longer lifetimes in high efficiency gratings are achieved by constant or periodic illumination of photorefractive materials to assure uniform charged distribution of electrons and maintenance of the ionic backbone grating.

Fabrication and applications of long-lifetime, holographic gratings in

A laser utilizes feedback from a volume holographic grating used as a wavelength standard to lock the laser output wavelength to its desired value. This feedback can be non-optical, wherein the holographic filter output is used to actively control the wavelength through an external control mechanism. This feedback can also be optical, wherein a volume hologram reflection grating is used to generate optical feedback into the laser gain.

Wavelength stabilized laser sources using feedback from volume holograms

A method of writing plane holographic gratings Bragg-matched for reflection in the infrared in a photorefractive material using shorter wavelength light through a face perpendicular to the grating planes. The writing beam wavelength is selected to be within the photorefractive sensitivity range of the crystal and the angles are chosen relative to the wavelength to define a reflection grating with a period such that counter-propagating reflection occurs at the desired IR wavelength. For reflection gratings at different wavelengths, either the transmission or the reflection mode geometry may be used. In the transmission mode, the writing beams are incident on the same side face while in the reflection made the writing is on opposite faces in an off-axis (non-counter-propagating) configuration. Anti-reflection coatings of the appropriate wavelengths are used on the crystal surfaces to reduce reflection losses and improve the diffraction efficiency of the grating.

Methods and devices for using photorefractive materials at infrared

An improved method for storing permanent holographic gratings in photorefractive materials for use in narrow band filters such as the H.sub.60 filter, as well as the filters themselves. The invention also provides an improved method of controlling the electric field and the nature of the photorefraction to minimize wavelength shifts and band broadening at a minimal reduction of diffraction efficiency.

Fixing method for narrow bandwidth volume holograms in photorefractive

Real time 'exclusive or' operation, image subtraction, intensity inversion, and first- and second-order differentiation is achieved by an interferometer with a phase conjugate mirror for retroreflection of two or more beams derived from a single beam by a beam splitter and recombined interferometrically by the beam splitter.

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Los Angeles, CA, United States of America

Victor Leyva