Negative-index metamaterial with polymer-embedded wire-pair structures at terahertz frequencies.

Experimental demonstrations of metamaterials with negative index of refraction have been limited to microwave and IR frequencies. In this work, a freestanding multilayer thin-film metamaterial showing a strong negative index of refraction at terahertz frequencies is fabricated and characterized. The metamaterial consists of periodically arranged H-shaped wire-pair resonant structures separated by a 14.5-microm-thick and enclosed between two 26-microm-thick layers of benzocyclobutene polymer. Complex reflection and transmission parameters of the metamaterial are measured via terahertz time-domain spectroscopy and are used for the extraction of refractive material properties. Our results show good agreement with finite element field simulations.