Designing dielectric resonators on substrates: Combining magnetic and electric resonances

Abstract

High-performance integrated optics, solar cells, and sensors require nanoscale optical components at the surface of the device, in order to manipulate, redirect and concentrate light. High-index dielectric resonators provide the possibility to do this efficiently with low absorption losses. The resonances supported by dielectric resonators are both magnetic and electric in nature. Combined scattering from these two can be used for directional scattering. Most applications require strong coupling between the particles and the substrate in order to enhance the absorption in the substrate. However, the coupling with the substrate strongly influences the resonant behavior of the particles. Here, we systematically study the influence of particle geometry and dielectric environment on the resonant behavior of dielectric resonators in the visible to near-IR spectral range. We show the key role of retardation in the excitation of the magnetic dipole (MD) mode, as well as the limit where no MD mode is supported. Furthermore, we study the influence of particle diameter, shape and substrate index on the spectral position, width and overlap of the electric dipole (ED) and MD modes. Also, we show that the ED and MD mode can selectively be enhanced or suppressed using multi-layer substrates. And, by comparing dipole excitation and plane wave excitation, we study the influence of driving field on the scattering properties. Finally, we show that the directional radiation profiles of the ED and MD modes in resonators on a substrate are similar to those of point-dipoles close to a substrate. Altogether, this work is a guideline how to tune magnetic and electric resonances for specific applications.

Self-assembled antireflection coatings for light trapping based on SiGe random metasurfaces

“…The performances of our device can be adapted and improved employing an optimized ad hoc buried oxide 43,45,64 and targeting specific wavelengths ranges with an appropriate choice of particles size. These possibilities bring the additional advantage of relaxing the need for expensive commercial UT-SOI 43,45 opening up the use of this method on other substrates (e.g.…”

“…45 However, in the present study the very thin BOX favors a more efficient light coupling within the Si wafer. 15,64 The scattering intensity of large islands exhibit three main peaks in the investigated spectral range (β, γ and δ, Fig.3 a), c), d) and e)). As for the previous case of small islands, the field intensity maps at ∼750 nm, ∼960 nm and ∼1600 nm, show that |E| is rather confined within the BOX, whereas |H| is well coupled into the substrate.…”

“…A relatively large vertical aspect ratio (η = h/r, where h is the particle's height and r = d/2 is the half of its base size) is necessary for the formation of intense and sharp resonances in dielectric Mie resonators 64 . While η remains low in pure Si islands, it is higher in SiGe Si 45,61 .…”

Mechanically Tunable Dielectric Resonator Metasurfaces at Visible Frequencies

“…6 It is known that high-permittivity low-loss dielectric resonators can support localized electric and magnetic resonances. 35 36 By changing the operation temperature, the material phase of the liquid crystal and thus the near-field interactions of the resonators operating in magnetic and electric modes are altered, resulting in a demonstrated tunability of the all-dielectric metasurface.…”

Enhanced second-harmonic generation from magnetic resonance in AlGaAs nanoantennas

“…Different particle geometries can be considered, but mainly spherical and cylindrical antennas have been dealt with to date. Nanodisks have recently proven versatile in tailoring of electric and magnetic response, stemming from two degrees of freedom: radius and height [14,15]. Also, as opposed to nanospheres, the fabrication of nanodisks is easily accessed by modern electron beam lithography, which enables a precise control of the nanodisk size and lattice geometries.…”