Isotropic Huygens dipoles and multipoles with colloidal particles

Abstract

Huygens sources are elements that scatter light in the forward direction as used in the Huygens-Fresnel principle. They have remained fictitious until recently where experimental systems have been fabricated. In this letter, we propose isotropic meta-atoms that act as Huygens sources. Using clusters of plasmonic or dielectric colloidal particles, Huygens dipoles that resonate at visible frequencies can be achieved with scattering cross-sections as high as 5 times the geometric cross-section of the particle surpassing anything achievable with a hypothetical simple spherical particle. Examples are given that predict extremely broadband scattering in the forward direction over a 1000 nm wavelength range at optical frequencies. These systems are important to the fields of nanoantennas, metamaterials and wave physics in general as well as any application that requires local control over the radiation properties of a system as in solar cells or bio-sensing

Broadband Antireflection with Halide Perovskite Metasurfaces

“…However, it was shown recently that low contrast between materials of particle and its environment can cause a broadband Kerker effect. [ 29,30 ] Interestingly, while in the references above contrast between materials was reduced artificially, halide perovskite has naturally low refractive index which can cause a broadband Kerker effect. It means that metasurface based on perovskite meta‐atoms can be non‐reflected and almost transparent, besides energy absorbed in the nanoparticle volume.…”

Helicity maximization in a planar array of achiral high-density dielectric nanoparticles

“…The magnitudes of electric and magnetic dipole polarizabilities of a NA with radius a = 85 nm, and their phase difference ∆ are calculated using the expressions from Mie theory and are plotted in Figure 2. This figure shows that at = 730 nm the electric and magnetic polarizabilities are approximately balanced, i.e., when | ee |/ 0 = | mm | and their phase difference is very close to zero, which means that the Kerker condition [63][64][65][66][67] is almost satisfied at that wavelength and hence the NA directs the scattered field in the forward direction (a source with zero back radiation is often referred to as Huygens source [68][69][70][71] ). The peak of mm at wavelength = 675 nm is often referred to as "magnetic resonance" of the NA.…”

Minimalist Mie coefficient model

“…Their properties are expressed with the Mie model in Eq. (10). By sweeping through the detuning and the absorption Mie angle, the maximum absorption of the trimer normalized to 3 × 3λ 2 /(8π) for a fixed side length can be identified.…”

“…(19)). The expressions become even more cumbersome when considering core-multishell or colloidal particles [9,10]. Moreover, electric and magnetic Mie coefficients of different multipolar orders can not be chosen independently.…”