Figure 1.

(a) The refractive index distribution along z-axis; (b) The band structure of considered material with parameters $n_0=1.26$, $\mathsf{\Delta }n=0.20$ and $\lambda =\pi /4$ mm; (c) relative amplitudes of reflected ($S_{11}$) and transmitted ($S_{21}$) signals of piece of material with thickness $\tau =3\pi \simeq 9.5$ mm.