Figure 6.

Comparison of theoretical predictions and the FEM simulation in respect of different periodic distances (solid lines represent the theoretical predictions, and dashed lines represent the FEM simulation results): (a) periodic distance $d={\lambda }_0/2$; (b) periodic distance $d={\lambda }_0$; (c) periodic distance $d=1.5{\lambda }_0$; (d) periodic distance $d=3{\lambda }_0$.