We study terahertz (THz) radiation transmission through grating-gate graphene-based nanostructures. We report on room-temperature THz radiation amplification stimulated by current-driven plasmon ...excitation. Specifically, with an increase of the dc current under periodic charge density modulation, we observe a strong redshift of the resonant THz plasmon absorption, followed by a window of complete transparency to incoming radiation and subsequent amplification and blueshift of the resonant plasmon frequency. Our results are, to the best of our knowledge, the first experimental observation of energy transfer from dc current to plasmons leading to THz amplification. Additionally, we present a simple model offering a phenomenological description of the observed THz amplification. This model shows that in the presence of a dc current the radiation-induced correction to dissipation is sensitive to the phase shift between oscillations of carrier density and drift velocity. And, with an increasing current, the dissipation becomes negative, leading to amplification. The experimental results of this work, as all obtained at room-temperature, pave the way toward the new 2D plasmon-based, voltage-tunable THz radiation amplifiers.
Compact Terahertz SPICE/ADS Model Liu, Xueqing; Ytterdal, Trond; Kachorovskii, Valentin Yu ...
IEEE transactions on electron devices,
06/2019, Letnik:
66, Številka:
6
Journal Article
Recenzirano
We describe a compact terahertz (THz) SPICE/advanced design system (ADS) model based on the extended Enz-Krummenacher-Vittoz (EKV) MOSFET model with channel segmentation but accounting for the new ...physics of the electron transport at THz frequencies. The model includes the distributed Drude inductance representing the electron inertia. The channel segmentation allows reproducing the nonuniformity in the electron density excitations and the plasmonic oscillations at THz frequencies. The model was validated by comparing the simulation results with the analytical THz detection theory and experimental data for silicon MOSFETs and FinFETs with gate lengths ranging from 60 to 800 nm. The good agreement between the simulated and analytical results and experimental data revealed the significance of the electron inertia and demonstrated the improved validity of the model at higher frequencies with an increase in the number of segments. The model was used to simulate a novel TeraFET THz spectrometer and the resonant TeraFET THz detector. These results show the model utility for device and circuit simulations at sub-THz and THz frequencies. An important application of the THz spectrometer simulation is in the design of a single field-effect transistor (FET) THz vector detector that could be extremely useful for 5G (and beyond) line-of-sight applications.
This paper reviews recent advances in the research and development of graphene-based plasmonic metamaterials for terahertz (THz) laser transistors. The authors’ theoretical discovery on THz laser ...transistors in 2007 was realized as a distributed-feedback dual-gate graphene-channel field-effect transistor (DFB-DG-GFET) in 2018, demonstrating ∼0.1 µW single-mode emission at 5.2 THz and ∼80 µW amplified spontaneous 1–7.6 THz emission at 100 K. To realize room-temperature, dry-cell-battery operating intense THz lasing with fast direct modulation, various approaches based on graphene plasmonic metamaterials are investigated and introduced as real device implementations, including (i) replacement of the laser photonic cavity with plasmonic cavity enormously improving the THz photon field confinement with larger gain overlapping, (ii) introduction of THz amplification of stimulated emission via current-driven graphene Dirac plasmons (GDPs), and (iii) controlling the parity and time-reversal symmetry of GDPs enabling ultrafast direct gain-switch modulation. Possible real device structures and design constraints are discussed and addressed toward coherent light sources applicable to future 6G- and 7G-class THz wireless communication systems.
We report on enhanced room-temperature detection of terahertz radiation by several connected field-effect transistors. For this enhanced nonresonant detection, we have designed, fabricated, and ...tested plasmonic structures consisting of multiple InGaAs/GaAs pseudomorphic high electron-mobility transistors connected in series. Results show a 1.63-THz response that is directly proportional to the number of detecting transistors biased by a direct drain current at the same gate-to-source bias voltages. The responsivity in the saturation regime was found to be 170 V/W with the noise equivalent power in the range of 10 -7 W/Hz 0.5 . The experimental data are in agreement with the detection mechanism based on the rectification of overdamped plasma waves excited by terahertz radiation in the transistor channel.
Plasmonic Helicity‐Driven Detector of Terahertz Radiation Gorbenko, Ilya V.; Kachorovskii, Valentin Yu; Shur, Michael S.
Physica status solidi. PSS-RRL. Rapid research letters,
March 2019, 2019-03-00, 20190301, Letnik:
13, Številka:
3
Journal Article
Recenzirano
Odprti dostop
A theory of the helicity‐driven plasmonic dc response of a gated two‐dimensional electron gas to terahertz (THz) radiation is developed. A general diagram of a plasmonic detector operating in ...different regimes is found and analytical equations describing all these regimes are derived. It is demonstrated that the helicity‐sensitive part of the response dramatically increases in the vicinity of the plasmonic resonances and oscillates with the phase shift between the excitation signals on the source and drain. The resonance line shape is an asymmetric function of the frequency deviation from the resonance. In contrast, the helicity‐insensitive part of the response is symmetrical. These properties yield significant advantage for using plasmonic detectors as helicity‐sensitive THz and far infrared spectrometers and interferometers.
A theory of the helicity‐driven plasmonic dc response of a gated two‐dimensional electron gas to terahertz radiation is developed. The helicity‐sensitive part of the response dramatically increases in the vicinity of the plasmonic resonances and oscillates with the phase shift between the excitation signals on the source and drain. The resonance line shape is an asymmetric function of the frequency deviation from the resonance.
This study reviews recent advances in room-temperature coherent amplification of terahertz (THz) radiation in graphene, electrically driven by a dry cell battery. Our study explores THz light–plasmon ...coupling, light absorption, and amplification using a current-driven graphene-based system because of its excellent room temperature electrical and optical properties. An efficient method to exploit graphene Dirac plasmons (GDPs) for light generation and amplification is introduced. This approach is based on current-driven excitation of the GDPs in a dual-grating-gate high-mobility graphene channel field-effect transistor (DGG-GFET) structure. The temporal response of the DGG-GFETs to the polarization-managed incident THz pulsation is experimentally observed by using THz time-domain spectroscopy. Their Fourier spectra of the transmitted temporal waveform through the GDPs reveals the device functions 1) resonant absorption at low drain bias voltages below the first threshold level, 2) perfect transparency between the first and the second threshold drain bias levels, and 3) resonant amplification beyond the second threshold drain bias voltage. The maximal gain of 9% is obtained by a monolayer graphene at room temperatures, which is four times higher than the quantum limit that is given when THz photons directly interact with electrons. The results pave the way toward tunable graphene plasmonic THz amplifiers.
Plasmonic interferometry is a rapidly growing area of research with a huge potential for applications in the terahertz frequency range. In this Letter, we explore a plasmonic interferometer based on ...graphene field effect transistor connected to specially designed antennas. As a key result, we observe helicity- and phase-sensitive conversion of circularly polarized radiation into dc photovoltage caused by the plasmon-interference mechanism: two plasma waves, excited at the source and drain part of the transistor, interfere inside the channel. The helicity-sensitive phase shift between these waves is achieved by using an asymmetric antenna configuration. The dc signal changes sign with inversion of the helicity. A suggested plasmonic interferometer is capable of measuring the phase difference between two arbitrary phase-shifted optical signals. The observed effect opens a wide avenue for phase-sensitive probing of plasma wave excitations in two-dimensional materials.
We study the electron temperature profiles for an inhomogeneous electron flow in the hydrodynamic regime. We assume that the inhomogeneity is due to a weakly nonuniform distribution of the momentum ...relaxation time within a spherically constricted area. We show that the temperature profile dramatically depends on the drive strength and the viscosity of the electron liquid. In the absence of viscosity, a Landauer-dipole-like temperature distribution, asymmetrically deformed along the current by the inelastic electron-phonon scattering, emerges around the inhomogeneity. We find that both the Landauer-dipole temperature profile and its asymmetry in the direction of the driving electric field exist in all dimensionalities and are, therefore, universal features of inhomogeneous hydrodynamic electron flow. We further demonstrate that the electron viscosity suppresses the thermal Landauer dipole and leads to the appearance of a "hot spot" exactly at the center of the constriction. We also calculate the phonon temperature distribution, which can be directly measured in experiments on thermal nanoimaging.
The effect of magnetic field on electron transport in graphene monolayers with various levels of impurity doping is studied. In samples with low impurity doping a square root magnetoresistance ...appears away from the Dirac point and no such magnetoresistance is observed in low mobility monolayers with high impurity doping. The difference in magnetoresistance is attributed to different types of scattering mechanisms in various samples. Our data for graphene monolayers with low impurity concentration shows a good agreement with theory over a wide range of magnetic fields.
The effect of short‐range scattering on the magnetotransport in monolayer graphene is discussed both theoretically and experimentally. It is shown that in a wide interval of magnetic field the magnetoresistance obeys a square root law. A simple physical picture of the discussed phenomenon is developed.
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