Dispersion engineering of two-dimensional photonic crystals composed of graphene-covered tellurium rods

Abstract

We investigate theoretically the frequency spectrum of two-dimensional photonic crystals using the well-known Dirichlet-to-Neumann (D-to-N) map method. The PhCs with square and triangular arrangements are built by graphene-covered tellurium rods which are surrounded by ion gel. The resulting frequency spectrum represents two forbidden frequency band, termed Bragg and graphene photonic band gaps. It is demonstrated that these forbidden band gaps can be controlled actively by altering the graphene chemical potential through applying external voltage. A tuning range of 4.81 THz and 5.31 THz was achieved for Bragg photonic band gap in square and triangular lattices, respectively, and a wide tuning range of 13.85 THz and 14.69 THz was achieved for graphene photonic band gap, when the chemical potential varies from μc = 0 to μc = 1.2 eV. These achievements may have future applications in some optical devices such as filters, sensors, nano-composites and energy storage devices in THz spectrum.