Doped-graphene plasmons have a wavelength of that is 1-3 orders of magnitude smaller than the light wavelength of . As a result, graphene plasmons are able to be confined down to volumes that are several orders of magnitude smaller than plasmons in noble metals. However, similar to metal plasmon, graphene plasmon suffers from high absorption loss. To balance the propagation length and modal size, graphene-based hybrid plasmonic terahertz waveguide was proposed. In this research we propose two novel graphene based hybrid plasmonic waveguides for the frequency of 3 terahertz. Theoretically we analyse them and the modal properties of the proposed structures are investigated by means of finite element method (FEM) using COMSOL Multiphysics software. Not only do we enhance field confinement in the gap but also we increase propagation length by the proposed structures. Doing this we tackle the trade off between confinement and propagation length.
