Figure 5

(a) and (b) Normalized scattering cross-section and phase response as a function of antenna width (fixed l = 170 nm h = 50 nm and spacer layer thickness 10 nm) under μ_c = 0.2 eV. (c) Comparison of the \(|{{\bf{E}}}_{z}|\) distribution for two gold antennas with different aspect ratio. (l × h × w = 170 × 50 × 20 nm and l × h × w = 170 × 50 × 50 nm for the upper and lower panel respectively). (d) and (e) Device structures for directional couplings to left-propagating TE and right-propagating TM mode respectively. The antenna center-to-center distances are 100 nm (d) and 240 nm (e). (f) Tunability illustration of central operation wavelength λ_d corresponding to (d) and (e). (g) and (h) Directivity curves under different μ_c for devices sketched in (d) and (e) respectively. (i) and (j) \(|{\bf{E}}|\) distributions of at the left port for (d) and right port for (e) respectively at 1.55 μm.