Using Huygens Multipole Arrays to Realize Unidirectional Needle-Like Radiation

Abstract

For nearly a century, the concept of needle radiation has captured the attention of the electromagnetics communities in both physics and engineering, with various types of contributions reoccurring every decade. With the near-term needs for highly directive, electrically small radiators and scatterers for a variety of communications and sensor applications, superdirectivity has again become a topic of interest. While it is well known that superdirective solutions exist and suffer ill-posedness issues in principle, a detailed needle solution has not been reported previously. We demonstrate explicitly, for the first time, how needle radiation can be obtained theoretically from currents driven on an arbitrary spherical surface, and we explain why such a result can only be attained in practice with electrically large spheres. On the other hand, we also demonstrate, more practically, how broadside radiating Huygens source multipoles can be combined into an end-fire array configuration to achieve needle-like radiation performance without suffering the traditional problems that have previously plagued superdirectivity.

Highly Subwavelength, Superdirective Cylindrical Nanoantenna

“…This goal was achieved by combining the metamaterialinspired paradigm [24] that employs near-field resonant parasitic (NFRP) elements to enhance and control the emissions from a driven source with the concept of having those elements generate higher-order modes (HOMs) [25]. However, in contrast to the array of elemental Huygens multipole radiators investigated in Ref.…”

Tunable Unidirectivity of Metal-Dielectric-Metal Plasmonic Nanoantennas With PT-Symmetric Potentials

“…The operating wavelength of λ = 870 nm can offer the best directionality with the narrowest α of 5.6 • for κ = 0.21 and 5.8 • for κ = 0.3 when N = 6 [63]. As a result, arranging the antennas into an array can achieve needle-like radiation [65].…”

Active coated nano rod antennas for enhanced and directive scattering phenomena

“…On the other hand, introducing asymmetry, by either off-setting the material layers [31,32] or by introducing appropriate perforations of the particles [33,34], was also found to stimulate the excitation of higher order modes, and thus to lead to a more interesting as well as directional performance characteristics. In addition hereto, super-directive behavior with needle-like radiation characteristics was recently demonstrated theoretically in spherical [35] and cylindrical [36] multi-layered structures.…”