Tunable and giant spatial Goos–Hänchen shifts in a parity-time symmetric Cantor photonic crystals incorporated with a centered graphene layer

Abstract

In this study, we present the spectral features of a one-dimensional parity-time symmetric layered structure was composed of two quasi-photonic crystals which submit to the Cantor sequence and a graphene layer is embedded in the center of the quasi-crystals. Exceptional points, reflection and transmission spectra and the spatial Goos-Hänchen (GH) shifts are investigated at two distinct terahertz regions in the presence and absence of the graphene layer and compared them. The effect of the modification of imaginary part of refractive index of constituting gain and loss media are also examined. Our results show that, the proposed structure display giant enhanced GS shifts which are tunable with the chemical potential of embedded graphene layer, while GH shifts are weak in the absence of graphene layer. Results display different value and sign of GH shifts for the zero and nonzero chemical potentials. Very extreme GH shifts are obtained by judicious choice of chemical potential and imaginary value of the refractive index of constituting materials. Our results display that not only the photonic bandgap edge modes, but also bandgap modes can support giant GH shifts at Terahertz frequencies. Functionally, these types of structures are very desirable for designing optoelectronic devices that can be adjusted by the amount of chemical potential.