Optical antennas consisting of metallic parts are analyzed using the Multiple Multipole Program (MMP), a semi-analytic
boundary discretization method. It is demonstrated that difficult numerical problems are caused because optical antennas
exhibit strong material dispersion, loss, and plasmon-polariton effects that require a very fine discretization. In addition
to standard dipole-type antennas, consisting of two pieces of metal, a new structure consisting of a single metal piece
with a tiny groove in the center is analyzed. This structure takes advantage of the Channel Plasmon-Polariton (CPP)
effect and exhibits a strong enhancement of the electric field in the groove. Furthermore, the groove type antenna
exhibits two resonance peaks when its dimension is much smaller than the wavelength. It is demonstrated that the
strengths and locations of the resonance peaks may be tuned within some range by tuning the length of the antenna.
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