(a) The Dirac-like cone dispersion near the point (k=0) calculated for a 2D square lattice PC with dielectric cylinders in air. The permittivity and radii of the cylinders are and ( is the lattice constant), and c is the speed of light in vacuum. The inset shows the unit cell of the PC. Adapted from . (b) The frequency dependence of the effective permittivity () and permeability () near the Dirac-like point frequency . The inset shows the nearly constant effective impedance obtained from and .