Plasmonic properties of asymmetric dual grating gate plasmonic crystals

We report on numerical study of dispersion properties and frequency dependent absorption characteristics of asymmetric dual grating gate terahertz (THz) plasmonic crystals. The study shows that the dispersion relations of plasmons in a two-dimensional electron gas (2DEG) capped with asymmetric dual grating gates have energy band gaps in the Brillion zones. Depending on the wave vector, the plasmons can have symmetrical, anti-symmetrical, and asymmetrical charge distributions that are different from the ones for uniform gratings case. Plasmons in the studied plasmonic crystal exhibit both tightly confined/weakly coupled behavior and propagating/strongly coupled behavior depending on the plasmonic modes. The responsivity of the plasmonic detector based on asymmetric dual grating gate does not monotonically decrease with the frequency, which is in contrast to the responsivity of uniform grating THz detectors. The cross-section of an asymmetric dual grating gate terahertz plasmonic device under THz illumination is represented, where excited plasmons are shown in red.