Transmission and Reflection of Terahertz Plasmons in Two-Dimensional Plasmonic Devices

Abstract

Abstract-Plasmons in two-dimensional semiconductor devices will be reflected by discontinuities, notably, junctions between gated and non-gated electron channels. The transmitted and reflected plasmons can form spatially-and frequency-varying signals, and their understanding is important for the design of terahertz detectors, oscillators, and plasmonic crystals. Using mode decomposition, we studied terahertz plasmons incident on a junction between a gated and a non-gated channel. The plasmon reflection and transmission coefficients were found numerically and analytically, and studied between 0.3 and 1 THz for a range of electron densities. At higher frequencies, we could describe the plasmons by a simplified model of channels in homogeneous dielectrics, for which the analytical approximations were accurate. At low frequencies, however, the full geometry and mode spectrum had to be taken into account. The results agreed with simulations by the finite-element method. Mode decomposition thus proved to be a powerful method for plasmonic devices, combining the rigor of complete solutions of Maxwell's equations with the convenience of analytical expressions.

Amplified-reflection plasmon instabilities in grating-gate plasmonic crystals

“…The geometrical asymmetry was shown to be crucial for efficient THz detection in plasmonic FETs 39 and is expected to be beneficial to achieve the low-threshold instabilities 16 , though the full theory of the asymmetry effect on the instability has yet to be developed. Further possible extensions of our model include the renouncement of quasi-optical approximation and full electrodynamic treatment of the plasmon reflection at the boundaries, including the excitation of the evanescent waves 23 . Within the same formalism, one can also consider the self-excitation of the edge plasmons travelling along the gated/ungated boundary 21 , which might have larger instability increments compared to the bulk modes.…”

“…According to the microscopic studies of wave reflection at the gated/ungated boundary 23 , the net amplitude of wave can be approximated as a sum of the 'fast' downstream and 'slow' upstream plasmons both in the gated and ungated sections. This so-called quasi-optical approximation provides sufficient accuracy for long ungated sections and/or high frequencies 24 .…”

Modeling terahertz plasmons in coupled semiconductor resonators

“…These parameters reflect those of realistic devices on which we have previously published [6], [7]. The interaction between plasmons supported by each The first model we used to calculate the resonant frequencies is based on mode matching [3]- [5], [7]. The fields in each section are first expanded into the waveguide eigenmodes.…”

“…Often, however, this approach can only provide a qualitative explanation but no quantitative agreement with experiment. More advanced models include a Fourier-integral approach [1], a transmission-line model [2], a mode-matching technique [3]- [5], and ubiquitous full-wave numerical solvers. There has, however, been little effort to compare these various approaches to each other.…”

Terahertz Plasmon Resonances in Two-Dimensional Electron Systems: Modeling Approaches

“…The resulting integral equation is then solved numerically. Another approach, used to study plasmon reflection and transmission at waveguide junctions, is modal analysis, in which the electromagnetic fields at both sides of a junction are expanded into the waveguide eigenmodes [5,16,22,[31][32][33][34]. Another example is the Wiener-Hopf technique [35,36], which has been used recently to derive expressions for plasmon transmission and reflection at a junction between two ungated 2DESs [37].…”