Metamaterial-based optical components for THz radiation
We present different metamaterial-based optical components that open exciting new ways to deliberately manipulate the spatial or spectral properties of terahertz (THz) radiation. The central scope of the paper is the design, fabrication and optical characterization of a 3-layer gradient index (GRIN) lens that allows one to strongly focus THz radiation to a spot diameter in the order of one wavelength. The GRIN lens is based on a specific metamaterial structure that is fully embedded in a polymer background matrix and thus provides a free-standing optics with high transmission and minimal Fresnel reflection. THz lenses with such strong focusing capabilities are especially intriguing with respect to the resolution enhancement of THz imaging systems.