Subwavelength Silicon Nanoblocks for Directional Emission Manipulation

Abstract

Manipulating the light emission direction and boosting its directivity have essential importance in integrated nanophotonic devices. Here, we theoretically propose a single dielectric silicon nanoblock as an efficient, multifunctional and ultracompact all-dielectric nanoantenna to direct light into a preferential direction. Unidirectional scattering of a plane wave as well as switchable directive emission fed by a localized emitter are demonstrated within the nanoantenna. The high directionalities are revealed to originate from a variety of mechanisms that can coexist within a single nanoblock, which contribute to the far-field radiation patterns of the outcoming light, thanks to the wealth of multipolar electric and magnetic resonances. The efficient beam redirections are also observed, which are sensitive to the local configurations of the emitter antenna coupled system. The designed antenna, with extreme geometry simplicity, ultracompact and low-loss features, could be favorable for highly sensitive sensing as well as applications in optical nanocircuits.

Toroidal‐Assisted Generalized Huygens’ Sources for Highly Transmissive Plasmonic Metasurfaces

“…[25] This kind of directional radiation is utterly desired in the design of many nanostructures particularly for controlling the light transmission in dielectric metasurfaces. [26,27] In other words, once the Kerker condition is satisfied, a meta-atom (also called a Huygens' source) can have either minimal backward scattering with maximal transmission level (first Kerker condition) or minimal forward scattering with maximal reflection efficiency (second Kerker condition). [28] Talking about boosting the transmission and radiation directivity with GKC, a workable strategy is to engage extra multipoles besides electric dipole (ED), magnetic dipole (MD), electric quadrupole (EQ), and magnetic quadrupole (MQ), and excite as many multipoles as possible.…”