This book addresses Nano-antennas that have a relatively wide bandwidth and is suitable for fast data communications. The properties of metals in the THz range have been investigated using the Drude model. The radiation characteristics of nanodielectric resonator antenna (NDRA) reflectarray at 633 nm have been examined. NDRAs with silver, copper, and aluminum supporting plane have been designed and analyzed for reflectarray and transmitarray antennas. A nanoreflectarray/transmitarray unit-cells with supporting plane that have been made from different metals have been explored.Design of 411 unit-cells in a circular configuration transmitarray using dielectric resonator antenna (DRA) has been carried out. The proposed transmitarray is used as a terahertz (THz) antenna at 4.5 THz, enabling wireless network on-chip interconnections for multi-core processor technology. Linearly polarized single beam and multi-beam transmitarrays fed by linearly polarized horn have been designed and investigated. A linearly-polarized receiving mode nanoantenna is designed for solar energy harvesting. The infrared nanoantenna is used to collect the solar radiation and converting it to electric energy.