## LIST OF FIGURES 

1 Schematic geometry of the planar-nanolayer-based medium. . . . . . . . . . . . . . . . 23 

2 Dispersion equation at ω = 3 . 4 × 10 15 rad / s for a periodic media as represented in Fig. 1 with w = 5 × 10 − 8 m and p = 4 . 5 × 10 − 7 m. The red lines marks the boundary of homogeneous-wave and evanescent-wave regimes in the dielectric, k$_{‖}$p = 7 . 711. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 

3 Isofrequency curves at different propagation constants β$_{c}$ < β < β$_{max}$ are shown in (a) for the first sheet and in (b) for the second sheet of the dispersion curve. Contour lines are labelled following the normalization βp . . . . . . . . . . . 25 

4 Behavior of the complex amplitude (left column) and argument (right column) of the wavefunction h$_{K}$ at different values of k$_{‖}$ and positive K corresponding to the first band (top), second band (middle) and third band (bottom). . . . . . 26 

5 Contour plot of the intensity | h$_{x}$ | 2 in the xy plane corresponding to a local- ized diffraction-free beam of normalized propagation constant βp = 8 . 503 and transverse frequency γp = 2 . 008 leading to ( k$_{‖}$p ) max = 8 . 737. Intensity distri- butions along the coordinate axes are shown at the top and left sides. Inset: Isofrequency curve where shaded region corresponds to the excited spatial bandwidth. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 

6 (a) Solutions k$_{x}$ of the equation (30), K ′′ s = 0, associated with different prop- agation constant β of the wavefields, in the layered structure of Fig. 1. (b) Azimuthal angle φ in the plane k$_{x}$K that corresponds to each solution of the aforementioned self-guiding condition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 

7 Transverse intensity | h$_{x}$ | $^{2}$( x, y ) for diffraction-free beams of βp = 7 . 899 and spatial frequency (a) γp = 2 . 552, (b) γp = 3 . 148, and (c) γp = 3 . 734. Insets: Isofrequency curve at βp = 7 . 899. The blue shade indicates the spectral win- dow in k$_{x}$ under excitation. Light blue regions refer to gap-induced frustrated excitation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 

