Band-gap engineering in two-dimensional periodic photonic crystals

A theoretical investigation is made of the dispersion characteristics of pl asmons in a two-dimensional periodic system of semiconductor (dielectric) c ylinders embedded in a dielectric (semiconductor) background. We consider b oth square and hexagonal arrangements and calculate extensive band structur es for plasmons using a plane-wave method within the framework of a local t heory. It is found that such a system of semiconductor-dielectric composite can give rise to huge full band gaps (with a gap to midgap ratio approxima te to 2) within which plasmon propagation is forbidden. The most interestin g aspect of this investigation is the huge lowest gap occurring below a thr eshold frequency and extending up to zero. The maximum magnitude of this ga p is defined by the plasmon frequency of the inclusions or the background a s the case may be. In general we find that the greater the dielectric (and plasmon frequency) mismatch, the larger this lowest band gap. Whether or no t some higher energy gaps appear, the lowest gap is always seen to exist ov er the whole range of filling fraction in both geometries. Just like photon ic and phononic band-gap crystals, semiconducting band-gap crystals should have important consequences for designing useful semiconductor devices in s olid state plasmas. (C) 2000 American Institute of Physics. [S0021-8979(00) 04418-2].