We investigated the propagation of electromagnetic waves in a finite superlattice bounded by a substrate and vacuum and separated from them by a buffer layer and a cap layer. In this realistic geometry, we show the existence of different kinds of localized and resonant modes whose behaviors are strongly dependent on the nature and thickness of the buffer and cap layers as well as on the width of the superlattice. These modes can be confined inside the superlattice or at its boundaries and give rise to different possibilities for the guidance of optical waves. The localized and resonant modes are obtained from an analytic calculation of the local and total densities of states within a Green's function formalism for electromagnetic waves ofs-pelarization (transverse electric). We also evaluate the reflection and transmission coefficients and compare their behaviors with the densities of states.
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