  In this paper the characteristic matrix method is used to study the
propagation of electromagnetic waves through one-dimensional lossy photonic
crystals composed of negative and positive refractive index material layers
with symmetric and asymmetric geometric structures with a defect layer at the
center of the structure. First, the positive index material defect layer is
considered, and the effects of the polarization and the angle of incidence on
the defect mode in the transmission spectra of the both structures are
investigated. The results show that the number of the defect modes in the
transmission spectra depends on the geometry (symmetric or asymmetric) of the
structure. In addition, it is shown that the defect mode frequency increases as
the angle of incidence increases. This property is independent of the geometry
of the structure. Then, for normal incidence, the negative index material
defect layer is considered, and the properties of defect modes for both
structures are investigated. The results can lead to designing new types of
transmission narrow filters.
