  Plasmonic double helical antennas are a means to funnel circularly polarized
states of light down to the nanoscale. Here, an existing design tool for single
helices is extended to the case of double helices and used to design antennas
that combine large chiroptical interaction strength with highly directional
light emission. Full-field numerical modeling underpins the design and provides
additional insight into surface charge distributions and resonance widths. The
experimentally realized double helical antennas were studied regarding their
polarization-dependent transmission behavior resulting in a large and broadband
dissymmetry factor in the visible range. Since the polarization of light is an
important tool for implementing logic functionality in photonic and quantum
photonic devices, these helices are potential building blocks for future
nanophotonic circuits, but also for chiral metamaterials or phase plates.
