Active toroid nano antenna excited by an electric Hertzian dipole

A novel toroid-structured coated nano particle (T-CNP) antenna with an active core (doped with rare earth ion Er³⁺) is studied in this paper. It is demonstrated that the active toroid-structured nano particle, when illuminated by an electric Hertzian dipole (EHD) (small current) element, acts as a strong radiator at its resonant frequency (around 600 THz). It is shown that the maximum peak of the power radiated by an EHD element could be increased more than 115 dB in the presence of an active nano-particle over its value when radiating into free space, i.e., its Purcell factor is more than 10¹¹.