We investigated the propagation of electromagnetic waves in a finite superl
attice bounded by a substrate and vacuum and separated from them by a buffe
r layer and a cap layer. In this realistic geometry, we show the existence
of different kinds of localized and resonant modes whose behaviors are stro
ngly 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 insid
e the superlattice or at its boundaries and give rise to different possibil
ities for the guidance of optical waves. The localized and resonant modes a
re obtained from an analytic calculation of the local and total densities o
f states within a Green's function formalism for electromagnetic waves of s
-polarization (transverse electric). We also evaluate the reflect:ion and t
ransmission coefficients and compare their behaviors with the densities of
states. (C) 1999 Optical Society of America [S0740-3232(99)02807-0].