Millimetre-Wave and Terahertz Amplification in a Travelling Wave Graphene Structure

The possibility of terahertz (THz) travelling wave amplification in graphene is demonstrated and analyzed by a hydrodynamic model based on the assumption of having two-dimensional relativistic electron liquid. Based on this model, the space charge density of electrons is calculated and the electrical conductivity of graphene as a function of frequency and wave vector is obtained. It is demonstrated that in the microwave to THz range of frequencies, the negative conductivity and thus gain can be obtained for drift velocities slightly greater than the phase velocity of the incident electromagnetic wave. This effect is used to introduce a graphene travelling wave amplifier for integrated mm-wave and THz systems. To optimize the gain, efficiency and bandwidth of the proposed travelling-wave amplifier, a slow wave grating structure is designed using Floquet mode analysis.