Mode Conversion in High-Definition Plasmonic Optical Nanocircuits

Symmetric and antisymmetric guided modes on a plasmonic two-wire transmission line have distinct properties and are suitable for different circuit functions. Being able to locally convert the guided modes is important for realizing multifunctional optical nanocircuits. Here, we experimentally demonstrate successful local conversion between the symmetric and the antisymmetric modes in a single-crystalline gold plasmonic nanocircuit with an optimally designed mode converter for optical signals at 194.2 THz. Mode conversion may find applications in controlling nanoscale light-matter interaction.