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

We theoretically investigate the properties of defect modes in one-dimensional symmetric defective photonic crystals. We consider three defective photonic crystal structures, air/[(AB)(Ns)A(alpha)(BA)(Ns)](NP)/air, air/[(AB)(Ns)AB(beta)A(BA)(Ns)](Np)/air, and air/{[(AB)(NS)AB(beta)A(BA)(Ns)]B-gamma}(Np-1)[(AB)(NS)AB(beta)A(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 A(alpha), the second has a composite defect, AB(beta)A, and the third has a interleaving defect B-gamma. The effect of thickness on the defect mode is studied by varying the parameters alpha, beta, and gamma, 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 N-p, we can have multiple defect modes, leading to a possible design of tunable multichannel filter. (C) 2015 Elsevier B.V. All rights reserved.