We theoretically investigate the excitation of plasmon resonances in a double-layer periodical graphene PT-symmetric microribbon structure. It is shown that the condition of PT-symmetry for graphene plasmonic structure is achieved at discrete frequencies for the set of realistic graphene parameters in terahertz frequency band, even at room temperature. The regimes of total reflection of THz wave at PT-symmetric plasmon resonance can be reached in periodical graphene microribbon structure.
We report on ultrahigh sensitive, broadband terahertz (THz) detectors based on asymmetric double-grating-gate (A-DGG)
high electron mobility transistors, demonstrating a record responsivity of 2.2 kV/W at 1 THz with a superior low
noise equivalent power of 15 pW/√Hz using InGaAs/InAlAs/InP material systems. When THz radiation is absorbed
strong THz photocurrent is first generated by the nonlinearity of the plasmon modes resonantly excited in undepleted
portions of the 2D electron channel under the high-biased sub-grating of the A-DGG, then the THz photovoltaic response
is read out at high-impedance parts of 2D channel under the other sub-grating biased at the level close to the threshold.
Extraordinary enhancement by more than two orders of magnitude of the responsivity is verified with respect to that for
a symmetric DGG structure.
The terahertz (THz) absorption spectra of plasmon modes in a grid-gated double-quantum-well (DQW) field-effect
transistor (FET) structute is analyzed theoretically and numerically using the scattering matrix approach and is shown to
faithfully reproduce strong resonant features of recent experimental observations of THz photoconductivity in such a
structure. No traces ofthe interwell plasmon is found in THz absorption spectra.