Enhanced THz radiation emission from plasmonic complementary Sierpinski fractal emitters.

We present a new class of plasmonic photoconductive THz emitters based on a complementary Sierpinski gasket fractal geometry. Due to the presence of sub-wavelength perforations on the surface of the antenna, these antennae operate in the plasmonic regime. By utilizing the unique self-similar and space filling of the tailored fractal surface and the plasmonic surface current spatial distribution, photoconductive THz emitters exhibiting superior performance (~80% increase in the emitted THz radiation power) to conventional bow-tie and Sierpinski gasket THz emitters are demonstrated. It is shown that the self-similarity of the surface plasmon current present on the antenna surface is responsible for this emission enhancement.