Accession Number : ADD008432

Title :   Large Aperture Phased Element Modulator/Antenna.

Descriptive Note : Patent,


Personal Author(s) : Richards,William E ; Taylor,Henry F

Report Date : 06 Jan 1981

Pagination or Media Count : 11

Abstract : An electro-optical modulator/antenna operates in the tunable diffraction grating mode to vary the magnitude of the zero diffraction order and consequently transmits optical information. A relatively thin slap of lithium niobate or equivalent electro-optic material has its lateral surfaces optically polished and its C-axis, or optical axis, running parallel to the polished lateral surfaces. At least one set of interdigital metallic electrodes are deposited on the face or just within the lateral surfaces to form, among other things, a diffraction grating that is orthogonally disposed with respect to the C-axis. When a potential source is coupled to the interdigital electrodes, the electric fields between adjacent electrodes change the crystal's index of refraction in accordance with the linear transverse Pockel's effect. The thin crystal having the electrodes substantially covering at least one of its lateral surfaces, thusly presents a large aperture modulator/antenna capable of modulating incident optical energy over a wide angle of incidence, for example, up to plus and minus 45 degrees. Because of the thinness of the crystal, transmissivity is good and losses are reduced. The cooperation between the diffraction grating phenomenon and the Pockel's effect greatly reduces if not totally eliminates the possibility of arcing between adjacent electrodes as the zero diffraction order is modulated since the potentials creating the modulating electric fields between adjacent interdigital electrodes are greatly reduced in this mode of operation. (Author)

Descriptors :   *Patents, *Antenna arrays, *Antenna apertures, *Electrooptics, *Phase modulation, Electrodes, Electric fields, Lithium niobates, Pockels cells, Axes, Optical properties, Optical data, Diffraction, Schematic diagrams, Crystals, Orthogonality, Cost effectiveness

Subject Categories : Electrooptical and Optoelectronic Devices

Distribution Statement : APPROVED FOR PUBLIC RELEASE