Plasmonic Cavity Formation by Circular and Spiral Corrugations

Abstract

Metal surfaces with sub-wavelength structures form a plasmon polariton-like surface mode, i.e., spoof-plasmon. The spoof-plasmon on a corrugated disk propagates radially and is reflected at the edge, resulting in formation of plasmonic cavity. With a concentric circular corrugation, the excited spoof-plasmons form an axisymmetric plasmonic cavity. With a spiral corrugation, the spoof-plasmons have non-zero orbital angular momenta and form a non-axisymmetric plasmonic cavity. Spoof-plasmons consisting of the plasmonic cavity transfer their angular momenta to radiation waves via the corrugated hollow waveguide by conserving their topological charges.