Resonant Properties of Circular Optical Nanoantennas of Homogeneous Disks.

We have studied the resonant properties of circular optical nanoantennas as well as other shapes of optical antennas without requiring any fitting parameters. This allows for a deeper insight into scaling behavior and do faster further research since a desired simple tool is now available to design such nanoantennas. The theory has been applied to design antennas supporting various resonances at predefined frequencies to respond to the desire to have multi resonant antennas for applications. Raman sensors are extremely broad band resonators. Such circular patch nanoantennas consist in tailoring the dispersion relation and the complex reflection coefficient at will by carefully selecting a particular stack of layers. We have made to characterize the resonance behavior of the potentially simplest optical nanoantennas which is also called nanowire antennas. The nanowire as a plasmonic cavity, a resonance occurs when the phase accumulated on a single round trip amounts to multiple of 2π. This phase is determined by the propagation constant of the plasmonic mode supported by the nanowire and an additional phase on reflection at the wire termination. By fitting many resonance positions with different nanowire lengths, the phase change on reflection is determined. Such results are obtained only for a few simplified geometries. Nanoantennas are made from an arbitrary stack of homogeneous disks. Increasing the radius of a single disk toward infinitely and increasing its thickness yielded the reflection coefficient of surface Plasmon polariton propagating along a single metallic interface at a planar termination. The obtained results were in good agreement with previous results. [ABSTRACT FROM AUTHOR]