Giant gaps in photonic band structures

We have investigated electromagnetic transmission through a one-dimensional waveguide along which stars of N' side branches were grafted at N equidistant sites, N and N' being integers. Analytic expressions are reported for the corresponding band structure for large N and for the transmission coefficient for any value of N and N'. Numerical results exhibit the existence of periodic very narrow photonic bands separated by large gaps, for N and N' similar to 5 to 10. The above generic and universal behaviors of these waveguides were confirmed by experiments using coaxial cables. [S0163-1829(98)50616-9].