Polarization Traffic Control for Surface Plasmons

摘要

A stone thrown into water produces waves that evenly spread out in all directions along the surface, but the symmetry patterns of the propagating waves can be changed if, for example, two stones are thrown in at different places and times. Similarly, surface plasmon polari-tons—electromagnetic waves bounded to a metal-dielectric interface—that are excited by different sources can also interfere with each other (1). These "surface plasmons," as they are commonly called, inherit one important property from photons: They are polarized, which turns out to be important for controlling their interference. On page 331 of this issue, Lin et al. (2) demonstrate a somewhat unexpected property of surface plasmons. Carefully designed nanostruc-tures can excite plasmons propagating in the direction uniquely defined by the type of polarization of the incident light. On page 328, Rodriguez-Fortufio et al. (3) show that near-field effects in the interference phenomena also allow unidirectional propagation of surface plasmons in a symmetric structure excited by circularly polarized light.