Wideband dual Vivaldi nano-antenna with high radiation efficiency over the infrared frequency band

Down scaling the well-known concept of metallic antennas to the optical frequencies offers unique advantages for novel photonic applications. One of the promising new applications is energy harvesting, using a rectenna. A key building block in such a system is an efficient antenna. A dual-Vivaldi nano-antenna is proposed to demonstrate the possibility of wideband operation at Infra-Red (IR) frequencies. According to our numerical results this nano-antenna has both high radiation efficiency and good impedance matching properties over a wide frequency band (more than 122%) in the IR frequency band. The design is based on the well-known Vivaldi antenna placed on Quartz substrate, but operating as a pair instead of a single element. Such pair of Vivaldi antennas oriented in opposite directions produces the main lobe in the broadside direction (normal to the axes of the antennas), rather than the usual peak gain along the axis (end-fire) of a single Vivaldi antennas.