Design and construction of an electro-optic RF metamaterial array

Abstract

Subwavelength metallic structures capable of creating strongly localized electromagnetic field with enormous enhancement under illumination/excitation are designed for direct radio frequency (RF) imaging. Three dimensional finite element method models are applied to investigate the electromagnetic field concentrations of two types of split ring resonators. Under appropriate linearly polarized illumination, a highly confined field located at the gap of the ring resonator is found due to strong scattering resonance. The numerical studies show that field enhancement as high as 6,800 is achieved for a planar D-shaped split ring resonator. The enhancement can be further increased through shrinking the gaps size or the ring width. Crescent shaped split ring resonator is designed for broadband application. It provides an enhanced bandwidth which is 1.15 times of the resonant frequency. The concentrated electromagnetic field facilitates nonlinear processes that find lots of applications. Optimized RF concentrators integrated with electro-optic modulators are demonstrated to directly modulate optical carrier. The combination of RF concentrator and EO modulator could enable a focal plane RF imager array that allows direct RF imaging, and significantly decrease RF aperture size and weight. Additional benefits include enhanced functionality such as inherent polarimetric imaging capability.