One-Way Extraordinary Optical Transmission and Nonreciprocal Spoof Plasmons

We introduce a concept of a nonreciprocal spoof surface plasmon: an electromagnetic wave supported by a structured conductor embedded in an asymmetric magneto-optical medium and exhibiting a nonreciprocal dispersion. It is demonstrated analytically and by first-principles electromagnetic simulations that, by breaking the time-reversal symmetry, nonreciprocal spoof surface plasmons enable a dramatic optical response: one-way extraordinary optical transmission.

Figure 1

Schematic of the layered structure supporting NSSPs and exhibiting one-way extraordinary optical transmission. Color arrows show the magnetization direction of the magnetic layers.

Figure 2

Nonreciprocal dispersion of (a) transversely confined NSSPs and (b) NSSPs coupled to the far field calculated by the modal matching technique for parameters $L_x=L_y=700\mathrm{nm}$, $a_x=a_y=330\mathrm{nm}$, and $\Delta =0.3$ to exaggerate the effect of nonreciprocity. The green and red lines show dispersion for forward ($k_x\ge 0$) and backward ($k_x\le 0$) SSPs, respectively. The dashed curves are calculated with the use of the simplified model of Eq. (1). The black line in (a) and (b) shows the unfolded and folded light line, respectively.

Figure 3

(a) Nonreciprocal EOT at 30° incidence on a perforated 300 nm thick PEC film and (b) the corresponding differential transmission. The dashed curves are the results of the minimal model. The solid lines and squares are the results of the modal matching and FEM, respectively. The substrate and cladding are 500 nm thick and are magnetized in opposite directions (Fig. 1); $L_x=L_y=700\mathrm{nm}$, $a_x=a_y=330\mathrm{nm}$, and $|\Delta |=0.06$.

Figure 4

Field profiles corresponding to two opposite directions of incidence (shown by arrows) on a PEC perforated film with asymmetrically magnetized cladding (Fig. 1). The structure is identical to that described in Fig. 3.

Figure 5

(a) Nonreciprocal EOT at 30° incidence on a 300 nm thick gold film with asymmetrically magnetized cladding and (b) the corresponding differential transmission. The structure dimensions are identical to that described in Fig. 3.