We conduct an investigation into optical nanoantennas in the form of a strip dipole made from aluminum. With the finite-difference time domain simulation both optical input impedance and radiation efficiency of nanostrip antennas are addressed. An equivalent circuit is presented as well for the nanostrip antennas at optical resonances. The optical input resistance can be adjusted by varying the geometric parameters of antenna strips. By changing both strip area and strip length simultaneously, optical input resistance can be adjusted for matching impedance with an external feeding or loading circuit. It is found that the optical radiation efficiency does not change significantly when the size of a nanostrip antenna varies moderately.
Broadband optical antennas are of interest as they can transmit more information like
traditional microwave UWB antennas. This paper presents a design of broadband optical antennas
with a concentric disk structure. An equivalent circuit for the optical antenna with a disk structure
is introduced. The broadband radiation at optical frequencies was demonstrated via the computer