arXiv subjects

J. Mikalopas

Publications and source records attributed to J. Mikalopas.

7 recordsLinked to original sources

arXiv2026

Parametric Resonance and RF-to-THz Frequency Conversion in Semiconductor Plasmonic Crystals

We show that plasma excitations in nanoscale field-effect transistor structures with periodic alternation of gated and ungated regions (plasmonic crystals) differ fundamentally from conventional plasmons in isolated gated or ungated regions. In contrast to the linear dispersion of purely gated plasmons and the square-root dispersion of ungated plasmons, these collective modes also exhibit a parabolic dispersion law characterized by a finite effective mass. We call these excitations "rotonic plasmons" emphasizing the analogy to roton-like excitations. The dynamics of rotonic plasmons are governed by a generalized Mathieu equation, describing either resonant or non-resonant parametric excitations of rotonic plasmons depending on damping. These nonlinear resonances can be efficiently driven by gate-voltage pumping, avoiding the spatial nonuniformities and electron drift velocity saturation effects associated with current-driven excitation. Gate-voltage pumping enables much higher terahertz (THz) power levels in plasmonic crystals. More importantly, in contrast to source-drain excitation, gate voltage pumping has the same gate voltage swing over large area transistors or transistor arrays. We develop a unified theory of rotonic plasmons and demonstrate their application for RF to THz frequency multiplication and THz generation. Starting from the general dispersion relation in plasmonic crystals based on coupled gated-ungated regions with two-dimensional electron gas, we derive the parabolic ("rotonic") plasmon spectrum and establish its analogy with roton-like excitations. The analysis predicts parametric instabilities in III-N and III-V plasmonic crystals under gate-voltage pumping. The results confirm that these systems can function as tunable, compact THz sources and detectors suitable for emerging 6G communications and sensing applications.

cond-mat.mes-hall↗

arXiv2025

Plasmonic Crystals with Tunable Band Gaps in the Grating Gate Transistor Structures

We developed a hydrodynamic model of plasmonic crystals formed in the current-driven grating gate transistor structures. The model demonstrates that the quality factor of plasmonic resonances could be increased by using ungated regions with high electron densities connecting multiple plasmonic cavities. The analytical and numerical calculations of the EM radiation absorption by the band plasmons show that the drive current makes all plasma modes optically active by breaking the symmetry of the plasma oscillations. This effect results in splitting plasmon resonant absorption peaks revealing the gaps in the plasmonic band spectrum tunable by current. The analyzed design could achieve resonant behavior at room temperature for plasmonic crystals implemented in various material systems, including graphene, III-V, III-N materials, and p-diamond. We argue that the resulting double-peak spectrum line in the terahertz range also facilitates the absorption at the gap frequency, typically in microwave range. Power pumping at the gap frequency enables excitation of the gap plasmons, promoting frequency conversion from microwave to THz ranges. The flexibility in the length of the ungated region for the investigated structures allows for an effective coupling with THz radiation, with the metal grating acting as a distributive resonant antenna. The applications of the presented results extend to THz communication systems, THz sensing and imaging, frequency conversion systems, and other advanced THz plasmonic devices.

cond-mat.mes-hall↗

arXiv2023

Plasma Instability and Amplified Mode Switching Effect in THz Field Effect Transistors with Grating Gate

We developed a theory of collective plasma oscillations in a dc current-biased field effect transistor with interdigitated dual grating gate and demonstrated a new mechanism of electron plasma instability in this structure. The instability in the plasmonic crystal formed in the transistor channel develops due to conversion of the kinetic energy carried by the drifting plasmons into electromagnetic energy. The conversion happens at the opposite sides of the gate fingers due to the asymmetry produced by the current flow and occurs through the gate finger fringing capacitances. The key feature of the proposed instability mechanism is the behavior of the plasma frequency peak and its width as functions of the dc current bias. At a certain critical value of the current, the plasma resonant peak with small instability increment experiencing redshift with increasing current changes to the blue shifting peak with large instability increment. This amplified mode switching (AMS) effect has been recently observed in graphene-interdigitated structures (S. Boubanga-Tombet et al., Phys. Rev. X 10, 031004 (2020)). The obtained theoretical results are in very good qualitative agreement with these experiments and can be used in future designs of the compact sources of THz EM radiation.

cond-mat.mes-hall↗

arXiv2021

Giant Inverse Faraday Effect in Plasmonic Crystal Ring

Circularly polarized electromagnetic wave impinging on a conducting ring generates a circulating DC plasmonic current resulting in an Inverse Faraday Effect in nanorings. We show that a large ring with periodically modulated width on a nanoscale, smaller or comparable with the plasmonic mean free path, supports plasmon energy bands. When a circularly polarized radiation impinges on such a plasmonic ring, it produces resonant DC plasmonic current on a macro scale resulting in a Giant Inverse Faraday Effect. The metamaterials comprised of the concentric variable width rings (plasmonic disks) and stacked plasmonic disks (plasmonic solenoids) amplify the generated constant magnetic field by orders of magnitude.

cond-mat.mes-hall↗

arXiv2020

Plasmonic Instabilities in Two-dimensional Electron Channels of Variable Width

Understanding of fundamental physics of plasmonic instabilities is the key issue for the design of a new generation of compact electronic devices required for numerous THz applications. Variable width plasmonic devices have emerged as potential candidates for such an application. The analysis of the variable width plasmonic devices presented in this paper shows that these structures enable both the Dyakonov-Shur instability (when the electron drift velocity everywhere in the device remains smaller than the plasma velocity) and the "plasmonic boom" instability that requires drift velocity exceeding the plasma velocity in some of the device sections. For symmetrical structures, the drifting current could be provided by an RF signal leading to RF to THz and THz to RF frequency conversion using the source and drain antennas and reducing losses associated with ohmic contacts. We show that narrow regions protruding from the channel ("plasmonic stubs") could control and optimize boundary conditions at the contacts and/or at the interfaces between different device sections. These sections could be combined into plasmonic crystals yielding enhanced power and a better impedance matching. The mathematics of the problems is treated using the transmission line analogy. We show that the combination of the stubs and the variable width channels is required for the instability rise in an optimized plasmonic crystal. Our estimates show that THz plasmonic crystal oscillators could operate at room temperature.

cond-mat.mes-hall↗

arXiv2018

Plasmons in ballistic nanostructures with stubs: transmission line approach

The plasma wave instabilities in ballistic Field Effect Transistors (FETs) have a promise of developing sensitive THz detectors and efficient THz sources. One of the difficulties in achieving efficient resonant plasmonic detection and generation is assuring proper boundary conditions at the contacts and at the heterointerfaces and tuning the plasma velocity. We propose using the tunable narrow channel regions of an increased width, which we call "stubs" for optimizing the boundary conditions and for controlling the plasma velocity. We developed a compact model for THz plasmonic devices using the transmission line (TL) analogy. The mathematics of the problem is similar to the mathematics of a TL with a stub. We applied this model to demonstrate that the stubs could effectively control the boundary conditions and/or the conditions at interfaces. We derived and solved the dispersion equation for the device with the stubs and showed that periodic or aperiodic systems of stubs allow for slowing down the plasma waves in a controllable manner in a wide range. Our results show that the stub designs provide a way to achieve the optimum boundary conditions and could also be used for multi finger structures - stub plasmonic crystals - yielding better performance of THz electronic detectors, modulators, mixers, frequency multipliers and sources.

physics.app-ph↗

arXiv2015

Current driven "plasmonic boom" instability in three-dimensional gated periodic ballistic nanostructures

A new approach of using distributed transmission line analogy for solving transport equations for ballistic nanostructures is applied for solving the three dimensional problem of the electron transport in gated ballistic nanostructures with periodically changing width. The structures with the varying width allow for modulation of the electron drift velocity while keeping the plasma velocity constant. We predict that in such structures biased by a constant current, a periodic modulation of the electron drift velocity due the varying width results in the instability of the plasma waves if the electron drift velocity to plasma wave velocity ratio changes from below to above unity. The physics of such instability is similar to that of the sonic boom, but, in the periodically modulated structures, this analog of the sonic boom is repeated many times leading to a larger increment of the instability. The constant plasma velocity in the sections of different width leads to the resonant excitation of the unstable plasma modes with the varying bias current. This effect (that we refer to as the super plasmonic boom condition) results in a strong enhancement of the instability. The predicted instability involves the oscillating dipole charge carried by the plasma waves. The plasmons can be efficiently coupled to the terahertz (THz) electromagnetic radiation due to the periodic geometry of the gated structure. Our estimates show that the analyzed instability should enable powerful tunable terahertz electronic sources.

cond-mat.mes-hall↗