Fast Construction of Dual-Field Superfocusing Based on Discrete Spatial Fourier Transform

A three-port plasmonic array is proposed to achieve a dual-field superfocusing using the forward-propagation method based on spatial Fourier transform (SFT). The algorithm of fast Fourier transform (FFT) is used to facilitate the design process. Both the electric and magnetic fields can be superfocused on the focal plane of z = 0.1λ (λ is the free-space wavelength) based on an effect of radiationless electromagnetic interference (REI). The full-widths of half-maximum (FWHMs) of both two fields are 0.060λ and 0.072λ, respectively. Besides, the metrics of the dualfield superfocusing are 1.67 and 1.39. The proposed theory can simplify the design process of superfocusing, and the plasmonic array with brief three ports can sufficiently facilitate the construction of the desired source. This work can be beneficial for the development of beam steering, sophisticated holography, and other applications of near- or far-field devices, etc.