Figure 14.

(a) Isofrequency curves for the second surface for a rectangular lattice with d_x=1, $d_y=\sqrt{2}$. The angle of incidence ψ=π/4, the dashed line κ_y=3.1113 and the ambient medium's contour ${\beta }^2={4.4}^2={\kappa }_x^2+{\kappa }_y^2$ are also shown. The predicted directions of propagation for scattered waves are shown by the arrows at A and B for ψ=0,β=4.40,κ_y=3.1113 and ψ=π/6,β=4.45,κ_y=2.225, respectively. (b) Real part of the displacement field for β=4.40, ψ=π/4, κ_y=3.1113 for the rectangular lattice. The Foldy method was used for 2000 gratings. (Online version in colour.)