Tunable omnidirectional multichannel filters based on dual-defective photonic crystals containing negative-index materials

Multiple defect modes may generate in one-dimensional dual-defective photonic crystals containing negative-index materials. The interference between the two kinds of defect states of the proposed structure is avoided. Therefore, the frequency, frequency interval and number of the defect modes corresponding to different kinds of defects can be tuned independently as desired. These defect modes inside the zero-(n) over bar gap are insensitive to the incident angle. It thus opens a promising way to fabricate omnidirectional multichannel filters with specific channels.