Electro-optic/metamaterial/electro-optic heterostructure defect induced resonant modes in reflectance spectrum of a band gap structure based on TiO2/SiO2 multilayers

Abstract

Extremely tunable one dimensional photonic band gap structures are proposed for optical integrated circuit (OIC) applications. Ideal crystal is made of alternating layers of TiO2 and SiO2 dielectric slabs. Two defective crystals are also considered by inserting composite defects of electro-optic and metamaterial slabs in the ideal structure. Optical characteristics of the proposed structures are tailored by using 4 × 4 transfer matrix method at the wavelength range of 410‒480 nm. Dependence of the crystals’ reflectance on the structural characteristics is systematically extracted by not only discussing the crystals reflectivity at various thicknesses of the layers qualitatively but also by extracting the values of the resonant modes' reflectivity amount and Q-factors quantitatively. Furthermore, the effect of the light incident angle, defect layers’ optical axis orientation and externally applied voltages to the ends of the electro-optic layers are considered. Results clearly reflect how easily the response of the proposed crystals could be tuned in practice. So that stop band gaps of as large as ~ 45 nm width and shifts of more than 35 nm might take place in the reflectance spectrum of the crystals by controlling the layers' size. But it is shown that the low size of the metamaterial layer does not play a serious role on the optical features of the crystals. Similarly it comes out that at least 100 V bias is needed to be applied to the ends of the electro-optic layer to see somewhat observable changes at resonant modes. Instead, by changing the incident angle from 0 to 80°, significant changes of the gap width as well as ~ > 30 nm shift in resonant modes are realized.