An intensity modulator for terahertz electromagnetic waves utilizing two-dimensional plasmon resonance in a dual-grating-gate high-electron-mobility transistor

We propose an intensity modulator utilizing two-dimensional plasmons (2DPs) in a dual-grating-gate high-electron-mobility transistor. The device primarily functions as a plasmon-resonant emitter in which the seeds of non-radiative longitudinal modes of 2DPs are efficiently converted into radiative transverse modes of terahertz (THz) electromagnetic waves. In this work, we numerically study the behavior of the mode conversion between 2DPs and THz electromagnetic waves as a function of the 2DP dispersion. The finite difference time domain analysis demonstrates that the coupling of THz electromagnetic waves and 2DPs changes with the electron drift velocity and with the sheet electron density in 2DPs. The analysis also reveals that the intensity of transmitted waves can be modulated over a wide THz range with an extinction ratio beyond 60% by optimizing the sheet electron density and the drift velocity under nominal area-factor condition (ratio of the 2DP area over the total active channel area) up to 0.6.