Northrop Grumman Systems Corporation

Accuwave Corporation

Arthur Bruce O'Connor

Amnon Yariv

George A Rakuljic

James T Hall

Seymour Levine

Victor Leyva

Koichi Sayano

Charles E Tyler

Susan M Raffensperger

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 holographic optical element (HOE) includes a substrate structure having rotational symmetry with respect to a rotational axis for rotatively supporting at least two holograms. A first hologram on the substrate structure in the path of a normally incident beam diffracts the beam by a first acute angle and in a first radial direction from the rotational axis to a first redirected path. A second hologram on the substrate structure in the first redirected path diffracts the beam by a different second acute angle and in an opposite second radial direction from the rotational axis to a second redirected path. As a result, the two holograms may be used to achieve a second redirected path at an angle to the rotational axis that has a size which is the difference between the size of the first angle and the size of the second angle. The substrate structure may include first, second, and third disc-shaped substrates bonded together so that the third substrate is in between the first and second substrates, and a thin-film interference filter may be included on the third substrate to suppress zero-order leakage through the first hologram. The filter element may include one of a dielectric stack, a transmission hologram, or a reflectance hologram. The first hologram may be imprinted to achieve total internal reflection of zero-order leakage through the second hologram. An additional interference filter may be included on either the output face of the HOE or on a separate window element in order to reflects any zero-order leakage from the second hologram. The HOE may also have Schmidt-type aberration correction superimposed on at least one of the holograms to compensate for spherical aberrations from an all spherical Cassegrain type of telescope.

Holographic laser scanner and rangefinder

Growing community of inventors

Redondo Beach, CA, United States of America

Arthur Bruce O'Connor