Harnessing superdirectivity in dielectric spherical multilayer antennas

Magnetic Purcell Enhancement in a Nanoantenna‐Spherical Bragg Resonator Coupled System

“…[31] This has made the recursive transfer matrix algorithm a powerful tool for the theoretical approach to studying different plasmonic and dielectric nanostructures. [34][35][36] In particular, we have already successfully applied this recursive transfer matrix method to demonstrate the feasibility of SBRs for engineering optical amplification and threshold gain for lasing. [29]…”

Mixtures of Multipoles—Should They Be in Your EM Toolbox?

“…In fact, a highly subwavelength superdirective system was attained with a metamaterial-inspired multilayered cylindrical structure and facilitated by a multipolar design approach. A number of works have since duplicated the concept [171] and have suggested ways to improve upon the original approach [172]- [174] and others have extended the concept to spherical versions [175], [176]. In all of these cases, the driven source has been taken to be in the exterior of the multilayered structure.…”

“…It is immediately apparent that both ENG and DPS regions were required for the desired outcome for this case. However, other 2D superdirective configurations with positive-only dielectric constants have been demonstrated [169] and have been emphasized in 3D with HDC materials in related spherical multilayered geometries [176].…”

Excitation of a homogeneous dielectric sphere by a point electric dipole

“…They are often called "morphology-dependent resonances", which emphasizes their dependence on the parameters of the sphere, such as the refractive index and the ratio of the radius of the sphere to the wavelength. From a physical point of view, the resonances are directly related to an efficient interaction of an incident electromagnetic wave with the sphere through the excitation the sphere's eigenmodes [6,7]. In order to achieve a directional scattering, it is necessary that the emission frequency of an electric dipole is close to one of the resonant frequency.…”

“…Usually, to obtain a directional radiation in one direction, it is considered sufficient to suppress radiation in the opposite direction using the interference of electric and magnetic modes of the scatterer [8,9]. While this method allows to get directional designs, it does not allow to always achieve the highest possible directivity, especially for electrically small DRA's with a high refractive index [7].…”