Electrodes on a photoconductive substrate for generation and detection of terahertz radiation

An antenna comprising a layer of a single photoconductive material and a plurality of spaced apart electrodes provided on said photoconductive material layer, each electrode having at least one facing edge which faces a facing edge of an adjacent electrode, a physical barrier being provided abutting a facing edge of at least one electrode, said barrier extending to at least the full height of said facing edge, wherein the facing edge of the at least one electrode is provided within a recess of the surface of said layer of photoconductive material such that said barrier is formed from said single photoconductive material, said recess including side-walls formed from said photoconductive material, and one of said side-walls of said recess providing said barrier.