Propagation of designer surface plasmons in structured conductor surfaces with parabolic gradient index.

In this work, we investigate the propagation of designer surface plasmons in planar perfect electric conductor structures that are subject to a parabolic graded-index distribution. A three-dimensional, fully vectorial finite-difference time-domain method was used to engineer a structure with a parabolic effective group index by modulating the dielectric constant of the structure's square holes. Using this structure in our simulations, the lateral confinement of propagating designer surface plasmons is demonstrated. Focusing, collimation and waveguiding of designer plasmons in the lateral direction is realized by changing the width of the source beam. Our findings contribute to applications of designer surface plasmons that require energy concentration, diffusion, guiding, and beam aperture modification within planar perfect electric conductors. .