A Terahertz Source and Detector device is provided that includes a nanostructured metasurface configured to transmit fully into a layer of absorbing material below the metasurface to achieve transparent conductivity in the visible spectrum region, wherein the metasurface is composed of crystalline material with very high mobility. The crystalline material can be composed of HgCdTe. The HgCdTe material can have a bandgap of about 700 meV. The intrinsic carrier concentration can be 1012 cm−3 at 300K.