Giant stop bands and defect modes in one-dimensional waveguide with dangling side branches

We investigate both the photonic and electronic band structure of a comb-li ke waveguide geometry in which dangling side branches are grafted along an finite one-dimensional waveguide. In a periodic (superlattice like) wavegui de, we report the opening-up of stop bands which originate both from the pe riodicity of the system and the resonant states of the grafted branches (wh ich play the role of resonators). Wide gaps (narrow bands) can be obtained by grafting several dangling side branches at every node. The stop bands st ill remain even for identical constituent materials. We also propose a tand em structure composed of two or several successive combs which differ by th eir physical characteristics that allows an ultrawideband filter. This beha vior results from the superposition of the bandgaps in the successive struc tures. The presence of a defect branch in the comb can give rise to localiz ed modes inside gaps. These states appear as very narrow peaks in the trans mission spectrum and therefore may have useful applications in the frame of photonic bandgap materials or electronic band engineering of nanostructure s.