Broadly tunable and bidirectional terahertz graphene plasmonic switch based on enhanced Goos-Hänchen effect

A plethora of research in recent years has been reported on free space optical switches based on Goos-Hänchen shift of the reflected light in the surface plasmon resonant systems. However, very little research has reported the tunable Goos-Hänchen shift in a fixed configuration. Thus, the main purpose of this investigation is to: (a) Bidirectional and tunable switch consisting of graphene plasmonic Kretchmann configuration is designed based on the analytical approaches at the terahertz frequency range, (b) Owing to tunable optical properties of graphene, the effect of different parameters including the chemical potential, temperature, and scattering time of graphene on the Goos-Hänchen shift are investigated. Our analytical calculations show that by strong coupling the incident light to the surface plasmons of the structure, giant Goos-Hänchen shift as high as 540 times the free space wavelength can be achieved. Furthermore, the application of white graphene as the substrate of graphene layer increases the propagation of the graphene surface plasmons while the required external voltage decreases. It is also shown that by considering the small change of chemical potential: Δμc = 0.4 eV (external voltage of ΔV = 0.5 V), the Goos-Hänchen shift variation of 440 λ0 (λ0 = 1.55 μm) can be easily provided. Finally, to verify our analytical results, the proposed structure is numerically simulated using finite-difference time-domain method. Based on these findings, this work present an alternate ways for improving both the tunability and magnitude of the Goos-Hänchen shift in a fixed configuration for bidirectional switching applications.