Investigation of resonant peaks in the symmetric and asymmetric multilayer narrowband transmission filters

The resonant transmission peaks in the asymmetric and symmetric multilayer narrowband transmission filters are theoretically investigated based on the transfer matrix method. In an asymmetric filter there exists only one resonant peak within the photonic band gap, and its position can be changed when the design wavelength is varied. In a symmetric filter, it is found that there are two resonant peaks. Using Bloch wave approximation, an investigation of these two resonant peaks has been made, and they are shown to correspond to the symmetric and antisymmetric field solutions in the defect layer.