SCREENING OF PLASMONS IN MODULATED 2DEGS BY GRATING GATES

Simple models for the dispersion relation for the plasmon modes of a two-dimensional electron gas (2DEG) take into account the presence of a coupling grating only by means of a sinusoidally periodic conducting layer, and generally include only a weak sinusoidal modulation of the electron density arising from any grating bias. We present here calculations of the energies of two-dimensional plasmons, including the periodic screening effect of a rectangular perfectly conducting grating coupler, in the case of strong modulation of the 2DEG with both rectangular and sinusoidal profiles. The calculations highlight the importance of the 2DEG modulation in determining the screened plasmon energies, and calculations of the plasmon charge density profiles show that as the modulation is increased, the plasmon oscillation becomes confined to regions of low 2DEG charge density with correspondingly low frequency.