Tuning of photonic band gaps in one dimensional chalcogenide based photonic crystal

A simple design of one dimensional gradual stacked photonic crystal (GSPC) structure has been proposed. The proposed structure, based on chalcogenide material, consists of a periodic array of alternate layers of As2S3 and air as the materials of high and low refractive indices respectively. The structure considered here has three stacks of periodic structures, each having five unit cells. The lattice period of successive stack is increased/decreased by a certain multiple (say gradual constant, e(gamma)) of the lattice period of the just preceding stack. For numerical computation, the transfer matrix method (TMM) has been employed. It is found that such a structure has wider reflection bands in comparison to a conventional dielectric PC structure, and the width of reflection bands can be enlarged as well as shifted towards higher/lower frequency by increasing/decreasing the value of the gradual constant. Hence, a GSPC structure can be used for broadening as well as tuning the photonic band gap and the bandwidth of gaps can be tuned to a desired wavelength region by choosing appropriate value of gamma (positive or negative). (C) 2011 Elsevier B.V. All rights reserved.