Fano-resonances in High Index Dielectric Nanowires for Directional Scattering

Abstract

High refractive index dielectric nanostructures provide original optical properties thanks to the occurrence of size-and shape-dependent optical resonance modes. These modes commonly present a spectral overlap of broad, low-order modes (e.g. dipolar modes) and much narrower, higher-order modes. The latter are usually characterized by a rapidly varying frequency-dependent phase, which -in superposition with the lower order mode of approximately constant phase -leads to typical spectral features known as Fano resonances. Interestingly, such Fano resonances occur in dielectric nanostructures of the simplest shapes. In spheroidal nanoparticles, interference between broad magnetic dipole and narrower electric dipole modes can be observed. In high aspect-ratio structures like nanowires, either the electric or the magnetic dipolar mode (depending on the illumination conditions) interferes with higher order multipole contributions of the same nature (electric or magnetic). Using the analytical Mie theory, we analyze the occurrence of Fano resonances in high-index dielectric nanowires and discuss their consequences like unidirectional scattering. By means of numerical simulations, we furthermore study the impact on those Fano resonances of the shape of the nanowire cross-sections as well as the coupling of two parallel nanowires. The presented results show that all-dielectric nanostructures, even of simple shapes, provide a reliable low-loss alternative to plasmonic nanoantennas. arXiv:1801.05601v1 [physics.app-ph]

Broadband and Highly Directional Visible Light Scattering by Laser-Splashed Lossless TiO2 Nanoparticles

“…Following this, Yuan Hsing Fu et al observed the directional scattering behavior of silicon nanoparticles in the visible light range [19]. Later on, a series of work has been carried out to improve the directional scattering efficiency and its operation wavelengths by other mechanisms, such as the Fano resonance [18,20] and the multibody enhanced electric field [21].…”

Computational study of film morphology impact on light absorption in particulate Ta3N5/Si photoanodes for water splitting

“…The impact of shape on resonant-optical absorption in semiconductor has been studied in great detail in literature [86]. This higher optical absorption of deformed particles can be associated with better coupling of light to resonance mode of deformed (rectangular) particles [86,87]. This observation suggests that the guidelines established in this work are applicable to particulate semiconductor photoanodes composed of non-spherical particles.…”

“…The deformed particle shows slightly higher optical absorption. The impact of shape on resonant-optical absorption in semiconductor has been studied in great detail in literature [86]. This higher optical absorption of deformed particles can be associated with better coupling of light to resonance mode of deformed (rectangular) particles [86,87].…”