Figure 13.

(a) Isofrequency contours for the first surface for the square lattice with d_x=1.0, d_y=1.0. The ambient medium's contour for β=4.40 is the dashed circle ${\beta }^2={\kappa }_x^2+{\kappa }_y^2$. (b) Isofrequency curves for the second surface. The dashed line κ_y=3.1113 has been drawn to correspond with Bloch waves in the vertical direction for β=4.40, ψ=π/4. The boundary of the irreducible Brillouin zone ΓXMY is also shown. (c) Close-up of isofrequency contours around β=4.40. (d) Star-like features of the dispersion curves for β=4.40 at M and collection of light circles for the square lattice (note the multiple intersections of the light lines at Dirac-like points). (Online version in colour.)