Photonic and Omnidirectional Band Gap Engineering in One-Dimensional Photonic Crystals Consisting of Linearly Graded Index Material

Engineering of photonic and omnidirectional band gaps has been demonstrated theoretically in one-dimensional photonic crystals (1-D-PCs) containing linearly graded and constant refractive index materials. The reflection spectra, photonic band gap spectra, reflection phase shift, and electric field distribution have been obtained by transfer matrix method in the 200-800 THz region. It has been found that the number of photonic bands increases with layers thickness. The omnidirectional band gap in a quarter-wave stacking arrangement of such PC has also been obtained. Results show that different constituted homogeneous layers can change the omnidirectional band gap remarkably. Moreover, we have demonstrated that photonic bandwidths can also be controlled by the contrast of initial and final refractive index of the graded layers.