Electromagnetic mode density for finite quasi-periodic structures

The transmission properties of quasi-periodic Cantor-like and Fibonacci photonic bandgap structures that have the same optical paths are studied and compared with one-dimensional, finite, N-period stacks. The electromagnetic mode densities and group velocities are also discussed. We show that the density of modes at the edge of the bandgap is greater for Cantor-like multilayers, so at the band edge a sharp decrease in the group velocity is found.