ABSTRACT
Like most of the other topics discussed in this book, the propagation of waves in periodic composite media also has a long history. Brillouin’s book on periodic structures (Brillouin (2003)), first published in 1946, gives a concise history of early developments in the field. The phenomenon of dispersion in a medium, where different frequency components of a wave travel at different phase velocities, was explained by Lord Kelvin using a periodic spring-mass model. Lord Rayleigh’s early work (Rayleigh, 1887) on the interaction of light with periodic layered media showed that such materials can exhibit band gaps in the frequency spectrum. Wave propagation is forbidden at these frequencies and the incident energy is usually reflected from the medium. The related phenomena of dispersion and band gaps in periodic media are responsible for a large range of interesting effects such as the iridescent colors in a peacock’s plumage.
