Terahertz Plasmonic Instability of a Double-layer Two-dimensional Electron System

Solid-state on-chip radiation devices based on plasmonic waves of two-dimensional electron gases (2DEGs) have vast application prospects in terahertz (THz) band. In this work, we adopt a hydrodynamic model to analyze the mechanism of the THz plasmonic wave excitation in a double-layer 2DEG system, where the electron drift velocity exists only in one 2DEG layer and the other is static. The result shows that the plasmonic instability occurs when the Doppler shifted slow wave in the drifted 2DEG layer synchronizes with the forward wave in the static 2DEG layer. To explore the principal rules guiding the device design, the critical factors that influencing the wave frequency and growth rate are also discussed, including the effects of the convection velocity, the electron densities, and the dielectric thicknesses.