As for early physical embodiments, three-dimensional electromagnetic lattices of intersecting straight wires developed by (Bracewell, 1954) and (Rotman, 1962) provided an effective medium for waves with wavelength sufficiently long compared with the lattice spacing. Properties were similar to those of neutral plasma.
Stop bands for waves occur in periodic particulate composites (Kinra and Ker, 1983) but not in random ones.
References
Bracewell, R., 1954, Wireless Engineer (Iliff and Sons Ltd., London), 320.
Rotman, W., 1962, IRE Trans. Antennas Propag AP10, 517- 526.
V. K. Kinra, E. Ker, An experimental investigation of pass bands and stop bands in two periodic particulate composites, International Journal of Solids and Structures 19, 393-410, 1983.