Broadband low-loss metamaterial-enabled devices

Artificially designed and structured electromagnetic materials, also known as metamaterials, allow the engineering of exotic electromagnetic properties, which in turn offers control over various wave-matter interactions, such as refraction, absorption, and radiation. Most reported metamaterials, both in the microwave and optical ranges, are limited either by a narrow bandwidth of operation and/or by significant absorption loss, both of which impede their integration into practical devices. Once these limitations have been overcome, broadband and low-loss metamaterials have the potential for providing great benefit to various engineering disciplines, including antennas, microwaves, terahertz, and photonics. Here, we present an overview of several recent advances in broadband and low-loss metamaterial-enabled devices for both microwave frequency and optical wavelength applications. We first consider a broadband negligible-loss metamaterial functioning as a soft-surface lining the interior of a horn antenna, resulting in reduced side lobe levels and cross-polarization. Next, we present a broadband transformation optics lens that produces multiple highly directive beams from a single isotropically radiating monopole antenna. Thirdly, we examine an ultra-thin anisotropic metamaterial coating that enhances the impedance bandwidth of a monopole to over an octave, while simultaneously preserving the radiation pattern quality. Next, we discuss a new broadband EBG design methodology which can be utilized in antenna isolation applications. Lastly, we will include an optical example that involves a dispersion-engineered broadband flat-top band-pass metamaterial filter with suppressed in-band variation of the group delay.