  In this paper, the localized surface modes in a defective multilayer
structure has been investigated. It is shown that the defective multilayer
structures can support two different kind of localized modes depending on the
position and the thickness of the defect layer. One of these modes is localized
at the interface between the multilayer structure and a homogeneous medium (the
so-called surface mode) and the other one is localized at the defect layer
(defect localized mode). We reveal that the presence of defect layer pushes the
dispersion curve of surface modes to the lower or the upper edge of the
photonic bandgap depending on the homogeneous medium is a left-handed or
right-handed medium (e.g. vacuum), respectively. So, the existence region of
the surface modes restricted. Moreover, the effect of defect on the energy flow
velocity of the surface modes is discussed.
