Sierpinski fractal plasmonic nanoantennas

We propose plasmonic Sierpiński gasket, a self-replicating fractal, with structural elements spanning from ∼100 nm to ∼5 µm made by standard electron beam lithography (EBL), metal deposition, and lift-off sequence. Such structures demonstrate light field enhancement from visible to far-IR spectral range and can be scaled up towards THz band. Numerical simulations show that as the fractal order is increased, the optical extinction band broadens from the visible light towards far-IR, achieving a light field enhancement of more than four orders of magnitude in the nano-gap proximity. Such antennas are prospective for IR–THz filter, detection, and emission applications. Fundamental mode simulation of Sierpiński fourth-order fractal gold nanoantenna with 10 nm nano-gap, made by EBL and lift-off.