Properties of defect modes in one-dimensional symmetric defective photonic crystals

• Defect modes in three model structures of defective photonic crystals are analyzed.
• The positions and number of defect modes are strongly dependent on thickness of defect layer.
• With the multiple defect modes, the structures can be used as multichannel filters.

We theoretically investigate the properties of defect modes in one-dimensional symmetric defective photonic crystals. We consider three defective photonic crystal structures, air/[(AB)NsAα(BA)Ns]Np/air, air/[(AB)NsABβA(BA)Ns]Np/air, and air/{[(AB)NsABβA(BA)Ns]Bγ}Np−1[(AB)NsABβA(BA)Ns]/air, where A and B are respectively taken to be the high- and low-index dielectric materials. The first has a defect layer of Aα, the second has a composite defect, ABβA, and the third has a interleaving defect Bγ. The effect of thickness on the defect mode is studied by varying the parameters α, β, and γ, respectively, for the above model structures. It is found that the positions and the number of defect modes can be significantly changed due to the change in the defect thickness. In addition, by increasing the repeated number Np, we can have multiple defect modes, leading to a possible design of tunable multichannel filter.

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