Broadband spin-controlled surface plasmon polariton launching and radiation via L-shaped optical slot nanoantennas

Broadband spin-controlled surface plasmon polariton (SPP) launching and radiation via L-shaped optical slot nanoantennas are proposed and demonstrated experimentally. The phase retardation and spectra overlapping between two resonant plasmon modes in the L-shaped optical slot nanoantenna lie at the origin of this effect. SPP launching in two perpendicular directions are controlled by the spin of the incident light. Broadband directional launching of SPPs is achieved and the extinction ratio keeps larger than 7 dB within a wavelength range of 150 nm. Furthermore, the photon spin of SPP radiation via the L-shaped optical slot nanoantennas is controlled by SPP propagation directions. These investigations provide a route for spin-controlled nanophotonic applications.