We have studied numerically spectral features of 1D dielectric stacks such as transmission spectrum, density of modes and the intensity of the electric field. The calculations have been performed using equivalently the transfer and the scattering matrix.
We have focused particularly on the cases of Fibonacci and triadic Cantor set stacks, where the spectrum is expected to display a fractal structure, and also periodic stacks. The transmission spectrum and density of modes near band gaps show narrow modes with very high density. The electric field intensity of these modes, when plotted in k-x space, shows puzzling behaviors, e.g. strong field enhancement and localization. Such modes may lead to a strongly enhanced Purcell effect and to a better understanding of the mode selection process in the case of negative absorption medium (gain material) – "random lasing".