Deceleration of terahertz plasma waves (plasmons) in tapered graphene-insulator-graphene heterostructure is studied. It is shown that the plasmon energy velocity can become several times smaller as compared to that near the taper apex.
We explore current-driven Dirac plasmon dynamics in monolayer graphene metasurfaces. DC-current-induced complete suppression of the graphene absorption is experimentally observed in a broad frequency range followed by a giant amplification (up to ∼ 9 % gain) of an incoming terahertz radiation at room temperature.
We analyze the pumping of the graphene-based laser heterostructures by infrared radiation using the numerical model. To enable the injection of sufficiently cooled carriers into the graphene layer (GL) leading to the interband population inversion, we propose to use the graded-gap black-PxAs1 − x absorption-cooling layers. Our calculations are based on the thermodiffusion-drift carrier transport model. We demonstrate that the proposed optical pumping method can provide an efficient injection of the cool electron–hole plasma into the GL and the interband population inversion in the GL. Since the energy gap in b-As layer can be smaller than the energy of optical phonons in the GL, the injected electron–hole plasma can be additionally cooled down to the temperatures lower than the lattice temperature. This promotes a stronger population inversion that is beneficial for realization of the GL-based optically pumped terahertz and far-infrared laser, plasmon emitters, and the superluminescent downconverters. We also compare the efficiency of optical pumping through the graded-gap and uniform absorbing-cooling layers.
Amplification of terahertz plasmons in tapered metal-insulator-graphene heterostructure is studied. It is shown that the plasmon energy density and the energy flux can become more than two orders of magnitude greater as compared to the same values in active pristine graphene.
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.
Linear and gapless energy spectrum of graphene carriers enables population inversion under optical and electrical pumping. We first theoretically discovered this phenomenon and demonstrated experimental observation of single-mode THz lasing with rather weak intensity at 100K in current-injection pumped graphene-channel field-effect transistors (GFETs). We introduce graphene surface plasmon polariton (SPP) instability to substantially boost the THz gain. We demonstrate our experimental observation of giant amplification of THz radiation at 300K stimulated by graphene plasmon instabilities in asymmetric dual-grating gate (ADGG) GFETs. Integrating the graphene SPP amplifier into a GFET laser will be a promising solution towards room-temperature intense THz lasing.
This paper reviews recent advances in the terahertz (THz) graphene-based 2D-heterostructure lasers and amplifiers. The linear gapless graphene energy spectrum enables population inversion under optical and electrical pumping giving rise to the negative dynamic conductivity in a wide THz frequency range. We first theoretically discovered these phenomena and recently reported on the experimental observation of the amplified spontaneous THz emission and single-mode THz lasing at 100K in the current-injection pumped graphene-channel field-effect transistors (GFETs) with a distributedfeedback dual-gate structure. We also observed the light amplification of stimulated emission of THz radiation driven by graphene-plasmon instability in the asymmetric dual-grating gate (ADGG) GFETs by using a THz time-domain spectroscopy technique. Integrating the graphene surface plasmon polariton (SPP) oscillator into a current-injection graphene THz laser transistor is the most promising approach towards room-temperature intense THz lasing.
The cross shape of the cut-off wavegulde cross-section enables to fix the E- and H-planes dielectric inserts or resonance sizes by means of projections. The quartz and leucosapphire monocrystals are used as die- lectric material for designing band-pass filters of millimetric wave band, thus ensuring the inserts geometric dimensions sufficient for manufacturing process and unloaded Q of the working types of electromag- netic modes excited in the insert. The paper shows the results or calcu- lating and designing 8-millimeter wave-band filters on the basis or cross-shape cut-off waveguldes partially filled with leucosapphire mono- crystal in the E-plane of the wavegulde.
We study instability of plasmons in a dual-grating-gate graphene field-effect transistor induced by dc current injection using self-consistent simulations with the Boltzmann equation. With ultimately high-quality graphene where the electron scattering is only limited by acoustic phonons, it is demonstrated that a total growth rate of the plasmon instability, with the terahertz/mid-infrared range of the frequency, can exceed 4 X 1012 s-1 at room temperature, which is an order of magnitude larger than in two-dimensional electron gases based on usual semiconductors. We show that the giant total growth rate originates from cooperative promotion of the so-called Dyakonov-Shur and Ryzhii-Satou-Shur instabilities.
The polarization conversion of terahertz radiation by the periodic array of graphene nanoribbons located at the surface of a high-refractive-index dielectric substrate (terahertz prism) is studied theoretically. Giant polarization conversion at the plasmon resonance frequencies takes place without applying external DC magnetic field. It is shown that the total polarization conversion can be reached at the total internal reflection of THz wave from the periodic array of graphene nanoribbons even at room temperature.
We study theoretically and experimentally the plasmonic THz detection by the asymmetric dual-grating-gate HEMT at room temperature without source-to-drain bias. We derive the analytical expressions of photocurrents due to the plasmonic drag and ratchet effects, and we discuss about their frequency dependences. We also compare the theory to the experimentally obtained frequency dependence. It is demonstrated that they agree qualitatively well.
This paper reviews recent advances in the research and development toward the graphene-based terahertz (THz) lasers. Mass-less Dirac Fermions of electrons and holes in gapless and linear symmetric band structures in graphene enable a gain in a wide THz frequency range under optical or electrical pumping. The excitation of the surface plasmon polaritons in the population-inverted graphene dramatically enhances the THz gain. Photon-emission-assisted resonant tunneling in a double-graphene-layered nano-capacitor structure also strongly enhances the THz gain. Novel graphene-based heterostructures using these physical mechanisms for the current-injection driven THz lasing are discussed. Their superior gain-spectral properties are analyzed and the laser cavity structures for the graphene THz laser implementation are discussed.
This paper reviews recent advances in graphene plasmonic heterostructures for new types of terahertz lasers. We
theoretically discovered and experimentally manifested that the excitation of surface plasmons in population-inverted
graphene by the terahertz photons results in propagating surface plasmon polaritons with a giant gain in a wide terahertz
range. Furthermore, double graphene layer heterostructures consisting of a tunnel barrier insulator sandwiched with a
pair of gated graphene monolayers are introduced. Photoemission-assisted quantum-mechanical resonant tunneling can
be electrically tuned to meet a desired photon energy for lasing, resulting in enormous enhancement of the terahertz gain.
Current injection structures are also addressed.
This paper reviews recent advances in graphene active plasmonics and their applications to terahertz lasers and sensors.
We theoretically discovered and experimentally manifested that when the carrier population in graphene is inverted the
excitation of graphene plasmons results in propagating surface plasmon polaritons with giant gain in a wide THz range.
Furthermore, when graphene is patterned in a microribbon array by grating gate metallization, the structure provides
super-radiant plasmonic lasing with giant gain as well as ultrahigh sensitive detection at the plasmon modes in a wide
THz frequency range.
The recent advances in emission and detection of terahertz radiation using two-dimensional (2-D) plasmons in semiconductor nanoheterostructures for nondestructive evaluations are reviewed. The 2-D plasmon resonance is introduced as the operation principle for broadband emission and detection of terahertz radiation. The device structure is based on a high-electron-mobility transistor and incorporates the authors’ original asymmetrically interdigitated dual-grating gates. Excellent THz emission and detection performances are experimentally demonstrated by using InAlAs/InGaAs/InP and/or InGaP/InGaAs/GaAs heterostructure material systems. Their applications to nondestructive material evaluation based on THz imaging are also presented.
This paper reviews recent advances in graphene active plasmonic metamaterials for new types of terahertz lasers. We
theoretically discovered that when the population of Dirac Fermionic carriers in graphene are inverted by optical or
electrical pumping the excitation of graphene plasmons by the THz photons results in propagating surface plasmon
polaritons with giant gain in a wide THz range. Furthermore, when graphene is patterned in a micro- or nano-ribbon
array by grating gate metallization, the structure acts as an active plasmonic metamaterial, providing a super-radiant
plasmonic lasing with giant gain at the plasmon modes in a wide THz frequency range.
This paper reviews recent advances in emission and detection of terahertz radiation using two dimensional (2D) plasmons in semiconductor nano-heterostructures for nondestructive evaluations. The 2D plasmon resonance is introduced as the operation principle for broadband emission and detection of terahertz radiation. The device structure is based on a high-electron mobility transistor and incorporates the authors’ original asymmetrically interdigitated dual grating gates. Excellent terahertz emission and detection performances are experimentally demonstrated by using InAlAs/InGaAs/InP and/or InGaP/InGaAs/GaAs heterostructure material systems. Their applications to nondestructive material evaluation based on terahertz imaging are also presented.
We investigated the emission of terahertz radiation from a doubly interdigitated grating gates high electron mobility transistor. The experiment was performed using Fourier spectrometer system coupled with high sensitive 4 K Silicon bolometer under the vacuum. The observed emission was explained as due to the excitation of the plasma waves by means of hot 2D plasmons. We also investigated the optical stimulation of the plasma waves by subjecting the device to a CW 1.5 µm laser beam. Dependence of the emission on the gate bias (i.e. on electron density) was observed and interpreted as due to the self oscillation of the plasma waves.
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.
Polaritonic excitations in a layer with strong excitonic response are theoretically studied. The dielectric function of the layer is assumed in the Lorentzian form with only one excitonic pole taken into account. The dispersion as well as optical absorption spectra of polaritonic excitations in such a layer are calculated. Both cases of symmetric and asymmetric dielectric environment of the excitonic layer are considered. Special attention is paid to so-called slow radiative polaritons excited in the total reflection regime. The problem of the impact of the higher polariton modes on optical spectra of the excitonic layer is addressed for the first time.
Results of a theoretical investigation of the angle dependence of chromatic polarization conversion of the electromagnetic wave (EW) in a density-modulated two-dimensional (2D) electron system are presented. A giant enhancement of the polarization conversion efficiency is found to emerge under plasma oscillation resonance in the periodic 2D electron system. At normal incidence, the greatest polarization conversion takes place when the angle between the plane of incidence of the EW and the direction of the periodicity of the system (azimuthal angle)is equal to 45°. At oblique incidence, the value of the azimuthal angle, at shich the maximum polarization conversion in the system occurs, deviates from 45° depending on a particular value of the contrast ratio of dielectric constants of media surrounding the 2D electron system. The greater the contrast ratio, the smaller the deviation. In the total reflection regime, the total polarization conversion can be reached, if the electron scattering in the 2D electron system vanishes. In contrast to the refringence case, the frequency of the polarization conversion resonance deviates with the angle of incidence and azimuthal angle at the total reflection regime as a result of the field confinement in the vicinity of the 2D electron system. Numerical calculations are performed for the characteristic parameters of an actual 2D electron system in the electron inversion layer on p-Si at the terahertz frequencies.
The problem of spontaneous emission of free polaritons from two-dimensional (2D) excitonic system is solved for the case of asymmetric dielectric environment of 2D excitonic system. The dispersion and radiative decay rates of resonant polaritons are calculated. The most of attention is given to slow resonant polaritons whose phase velocity is less than the speed of light in the ambient medium. The conclusion is drawn that the slow resonant polaritons can be observed in time-resolved photoluminescence experiments on near-surface 2D excitonic systems at grazing angles of emission.
Results of a theoretical investigation of the polarization conversion of the electromagnetic wave (EW) in a density- modulated two-dimensional (2D) electron system are presented. A giant enhancement of the polarization conversion efficiency is found to merge under plasma oscillation resonance in the periodic 2D electron system. The cases of the normal and an oblique incidence of the external EW are considered. It is shown that in the total internal reflection regime the total polarization conversion can be reached if the electron scattering in the 2D electron system vanishes. Numerical calculations are performed with the characteristic parameters of an actual 2D electron system in the electron inversion layer on p-Si at the far- infrared frequencies. A solid angle in which the wavevector of the incident EW should reside in order to produce the greatest polarization conversion efficiency is calculated for different aspect fraction values of the periodic 2D electron system.
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