Controllable directive radiation of a circularly polarized dipole above planar metal surface

Abstract

We report unidirectional radiation of a circularly polarized dipole above planar metal surface, the radiation direction can be manipulated via changing the distance between the dipole and the surface. This phenomenon is unique for the combination of circularly polarized dipole and metal surface and does not happen for linearly polarized dipole on metal surface or circularly polarized dipole on dielectric surface. The underlying physics is analytically disclosed by the interference of two orthogonally-oriented dipole component with π/2 phase lag. A substantially different mechanism of introducing the vectorial nature of the dipole itself to control light emission distinguishes the present scheme from nanoantenna and provides a new degree of freedom in light emission engineering.

Optical forces from near-field directionalities in planar structures

“…2. The oscillation itself can be said to be the far-field directionality that the elliptical dipole gains when above a metallic surface [63]. The near-field directionality and therefore near-field forces can be directly controlled by the polarization of the dipole, which experimentally can be controlled via illuminating polarization.…”

Beam steering and impedance matching of plasmonic horn nanoantennas

“…Previously, plasmonic substrates (i.e. metallic ground-planes) were used to manipulate the nanoantennas' radiation pattern [18][19][20][21][22]. If a reflector ground plane is employed, directly emitted light from the nanoantenna and the reflected light from the ground plane can interfere with different phases based on the thickness and type of the substrate material, enabling one to control and engineer the far-field radiation pattern [18,22].…”

“…metallic ground-planes) were used to manipulate the nanoantennas' radiation pattern [18][19][20][21][22]. If a reflector ground plane is employed, directly emitted light from the nanoantenna and the reflected light from the ground plane can interfere with different phases based on the thickness and type of the substrate material, enabling one to control and engineer the far-field radiation pattern [18,22]. In [22], Ghadarghadr et al reported that the dipole nanoantenna far-field radiation can be engineered by changing the distance between the dipole and the reflecting surface, and showed beam steering can be achieved in any arbitrary direction, ranging from end-fire to broadside.…”

Control of fluorescence enhancement and directionality upon excitations in a thin-film system

“…In addition, the coupling strength between the excited fluorophores and SPPs is highly dependent on the distance between fluorophores and the reflecting surface, hereafter referred to the fluorophore-interface or dipole-interface distance [27,31]. Furthermore, together with the intrinsic absorption of the reflecting surface [27,31,32], the interference [33][34][35][36] between the fluorescence radiation and the reflected waves from the reflecting surface can also alter the decaying properties of the excited fluorophores, which are highly dependent on the fluorophore-interface distance too [31]. Therefore, if a dielectric spacer layer is introduced as a separation between the dye layer and the reflecting surface, by adjusting the thickness of the dielectric spacer, the resulting multilayer system can be used to manipulate the fluorescence lifetime [31][32][33][37][38][39][40][41][42][43] and the emission directionality [33][34][35][36], because the inclusion of the spacer layer allows us to precisely control the fluorophore-interface distance.…”