Large Aperture Phased Element Modulator/Antenna.
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 slab 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.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 19, 1978
- Accession Number
- ADD006106
Entities
People
- Henry F. Taylor
- William E. Richards
Organizations
- United States Department of the Navy