Design of graphene-based hybrid waveguides for nonlinear applications

Abstract

The extraordinary properties of a monolayer graphene can be effectively utilized in integrated optoelectronic devices. Therefore, the optical properties and the effective parameters on the graphene’s conductivity are calculated at the telecom wavelength 1.55 µm. Next, the different types of photonic and plasmonic hybrid waveguides based on graphene are designed for nonlinear applications such as frequency conversion processes. The fundamental proposed structure consists of a LiNbO3 layer, a single graphene layer and a dielectric gap between the graphene and LiNbO3 to support the nonlinear applications such as second harmonic generation. The waveguide’s performance is analyzed in terms of the intensity of electric field, LiNbO3 thickness, the gap refractive index, mode effective index and propagation loss while the graphene’s chemical potential is varied with an applied gate voltage. According to the results, a sudden rise in propagation loss at µc = 0.493 eV (where the permittivity of graphene is almost zero) is observed. At last, a plasmonic hybrid waveguide consisting of a silver strip and a graphene layer placed between the metal and LiNbO3 layer is presented and the effect of the graphene’s chemical potential on the mode effective index and the propagation length are studied.