Abstract

We examine optical phase conjugation and harmonic phase conjugation at microwave and millimeter wavelengths using an isotropic opto-mechanical array as the active medium. Such a medium, which can be regarded as a specialized class of artificial dielectrics, consists of a three-dimensional array of di-electric, metal, or metal coated spheres that are mechanically supported but free to roll or slide on either flat, transparent planes or strings. Theory asserts that these media form very deep translational index gratings, due to electrostrictive forces, that are suitable for nonlinear optical processes, such as phase conjugation. In particular, it is found that such a medium can easily achieve gain by using very low write beam powers, typically on the order of milliwatts per square centimeter. We examine medium dynamics from the perspective of the Langevin equations and find that typical optical index grating formation times are on the order of a few seconds at atmospheric pressures. However, these response times can be reduced to several milliseconds if the medium is maintained at an air pressure of a few torr.

© 1992 Optical Society of America