Tunable Unidirectional Coupling of Surface Plasmon Polaritons Utilizing a V-Shaped Slot Nanoantenna Column

Abstract

A polarization-sensitive V-shaped slot nanoantenna column is utilized to realize tunable unidirectional coupling of surface plasmon polaritons (SPP). Two plasmon resonant modes are excited in the V-shaped slot nanoantennas with xand y-polarized incident light, respectively. The electric fields of coupled SPP show different symmetries corresponding to that of the two resonant modes. Linear combinations of the two resonant modes result in asymmetric SPP intensity distributions. As a result, by controlling the incident polarizations, tunable unidirectional coupling of SPP to two opposite directions perpendicular to the column at different wavelengths are realized. A highest extinction ratio of 36.7 dB is achieved, and the extinction ratio keeps larger than 7 dB within a wavelength of 149 nm.

Directional and Singular Surface Plasmon Generation in Chiral and Achiral Nanostructures Demonstrated by Leakage Radiation Microscopy

“…Noteworthy, our theory reveals that maximum directivity is reached for α = 60˚. This important result is consistent with previous numerical simulations [29] which also predict maximum directional coupling for Λ-shaped structure array with α = 60˚. Although a finite difference time domain [29] based numerical resolution approach was adopted (see also [32] for related studies with lithographed Λ-shaped antennas but with a directionality along the ky axis), we showed that our analytical model based on dipolar approximation is in complete agreement with these results.…”

“…[13, 14]) showed the potential of LRM for polarization tomography and control which strongly motivates the present study of SPP directional propagation and vortex generation.In this letter, we report the implementation of LRM for probing the chirality of plasmonic nanostructures. Specifically, we achieved quantitative characterization of spin-controlled directional couplers consisting of rectangular nanoapertures arranged in T or Λ geometry [29,30] (see Figure1). On the one hand, we demonstrate unidirectional propagation of SPPs induced by a rectangular array made of the aforementioned chiral and achiral apertures.…”

“…Our result follows the methods discussed in refs. [29,30] (see also refs. [32][33][34] for related works).…”

Highly efficient singular surface plasmon generation by achiral apertures

“…Under the single dipole approximation (β = 0), we retrieve the results obtained by previous numerical simulations [28] which predicted a maximum directivity for apertures with α = 45…”

“…In agreement with the experimental results, we find that the angle α = 60 • yields the maximum value of the directivity. Under the single dipole approximation (β = 0), we retrieve the results obtained by previous numerical simulations [28] which predicted a maximum directivity for apertures with α = 45 • .…”