We propose and analyze a multifunctional THz device which can operate as a tunable switch and a filter. The device consists of a circular graphene nanodisk coupled to two nanoribbons oriented at $90^\circ$ to each other. The graphene elements are placed on a dielectric substrate. The nanodisk is magnetized by a DC magnetic field normal to its plane. The physical principle of the device is based on the propagation of surface plasmon-polariton waves in the graphene nanoribbons and excitation of dipole modes in the nanodisk. Numerical simulations show that 0.61T DC magnetic field provides transmission (regime ON) at the frequency 5.33 THz with the bandwidth 12.7$\%$ and filtering with the Q-factor equals to 7.8. At the central frequency, the insertion loss is around -2 dB and the reflection coefficient is -43 dB. The regime OFF can be achieved by means of switching DC magnetic field to zero value or by switching chemical potential of the nanodisk to zero with the ON/OFF ratio better than 20 dB. A small central frequency tuning by chemical potential is possible with a fixed DC magnetic field.
Structural coloration of natural surfaces often originates from the change of reflected colors depending on the viewing or illumination angle. Recently, the structural coloration of nanoplasmonic structures have attracted a great deal of attention due to high compactness, robust stability and high color-tunability, as well as high sensitivity to an incident angle. Here we report complementary plasmonic structures (CPS) for transmission structural coloration by tailoring a single spectral peak depending on the incident angle of light. The CPS features self-aligned silver nanohole and nanodisk a…
We report on the numerical and theoretical results of sub-THz and THz detection by a current-driven InGaAs/GaAs plasmonic Field-Effect Transistor (TeraFET). New equations are developed to account for the channel length dependence of the drain voltage and saturation current. Numerical simulation results demonstrate that the effect of drain bias current on the source-to-drain response voltage (dU) varies with the device channel length. In a long-channel TeraFET where plasmonic oscillations cannot reach the drain, dU is always positive and rises rapidly with increasing drain current. For a short …
We show that a periodic multi-grated-gate structure can be applied to THz plasmonic FETs (TeraFETs) to improve the THz detection sensitivity. The introduction of spatial non-uniformity by separated gate sections creates regions with distinct carrier concentrations and velocities, giving rise to harmonic behaviors. The resulting frequency spectrum of DC voltage response is composed of enhanced and suppressed regions. In the enhanced region, the amplitude of response voltage can be enlarged up to 100% compared to that in a uniform channel device. The distribution pattern of those regions is dire…
Driven by a myriad of potential applications such as communications, medical imaging, security, spectroscopy, and so on, terahertz (THz) technology has emerged as a rapidly growing technological field during the last three decades. However, since conventional materials typically used in microwave and optical frequencies are lossy or do not effectively respond at these frequencies, it is essential to find or develop novel materials that are suitable for device applications in the THz range. Therefore, there is wide interest in the community in employing novel naturally-occurring materials, such…
Terahertz (THz) band is considered as the next frontier in wireless communications. The emerging THz multiplexing techniques are expected to dramatically increase the information capacity of THz communications far beyond a single channel limit. In this work, we explore the THz frequency-division multiplexing modality enabled by novel add-drop multiplexer (ADM) design. Based on modular two-wire plasmonic waveguides fabricated using additive manufacturing and metallization techniques, we demonstrate four-port THz ADMs containing grating-loaded side couplers for operation at ~140 GHz carrier freq…
A key component for optical on-chip communication is an efficient light source. However, to enable low energy per bit communication and local integration with Si CMOS, devices need to be further scaled down. In this work, we fabricate micro- and nanolasers of different shapes in InP by direct wafer bonding on Si. Metal-clad cavities have been proposed as means to scale dimensions beyond the diffraction limit of light by exploiting hybrid photonic-plasmonic modes. Here, we explore the size scalability of whispering-gallery mode light sources by cladding the sidewalls of the device with Au. The …
Broadband electro-optic intensity modulators are essential to convert electrical signals to the optical domain. The growing interest in THz wireless applications demands modulators with frequency responses to the sub-THz range, high power handling and very low nonlinear distortions, simultaneously. However, a modulator with all those characteristics has not been demonstrated to date. Here we experimentally demonstrate that plasmonic modulators do not trade off any performance parameter, featuring - at the same time - a short length of 10s of micrometers, record-high flat frequency response bey…
Future wireless communication networks have to handle data rates of tens or even hundreds of Gbit/s per link, requiring carrier frequencies in the unallocated terahertz (THz) spectrum. In this context, seamless integration of THz links into existing fiber-optic infrastructures is of great importance to complement the inherent portability and flexibility advantages of wireless networks by the reliable and virtually unlimited capacity of optical transmission systems. On the technological level, this requires novel device and signal processing concepts for direct conversion of data streams betwee…
Graphene supports surface plasmon polaritons with comparatively slow propagation velocities in the THz region, which becomes increasingly interesting for future communication technologies. This ability can be used to realize compact antennas, which are up to two orders of magnitude smaller than their metallic counterparts. For a proper functionality of these antennas some minimum material requirements have to be fulfilled, which are presently difficult to achieve, since the fabrication and transfer technologies for graphene are still evolving. In this work we analyze available graphene materia…
Two types of novel graphene-based components, namely, filters and electro-optical switches in guided wave configuration are suggested and analysed. The filters differ from the known ones with collinear orientation of the input and output waveguides by geometry and symmetry. The components consist of a circular graphene disk and two nanoribbons oriented at $90^\circ$ to each other in the plane of the graphene layer. The graphene elements are placed on a dielectric substrate. We show that change in symmetry leads to a drastic change in the properties of the components. The physical principle of …
p-diamond field effect transistors (FETs) featuring large effective mass, long momentum relaxation time and high carrier mobility are a superb candidate for plasmonic terahertz (THz) applications. Previous studies have shown that p-diamond plasmonic THz FETs (TeraFETs) could operate in plasmonic resonant mode at a low frequency window of 200 GHz to ~600 GHz, thus showing promising potential for beyond 5G sub-THz applications. In this work, we explore the advantages of p-diamond transistors over n-diamond, Si, GaN and InGaAs TeraFETs and estimate the minimum mobility required for the resonant p…
Parametric Resonance and RF-to-THz Frequency Conversion in Semiconductor Plasmonic Crystals
Kingsborough College, The City University of New York（纽约市立大学金斯伯勒学院）；The Graduate School and University Center, The City University of New York（纽约市立大学研究生中心）；Rensselaer Polytechnic Institute（伦斯勒理工学院）；Electronics of the Future, Inc.（未来电子公司）
We show that Si MOSFETs, AlGaN/GaN HEMTs, AlGaAs/InGaAs HEMTs, and p-diamond FETs with feature sizes ranging from 20 nm to 130 nm could operate at room temperature as THz spectrometers in the frequency range from 120 GHz to 9.3 THz with different subranges corresponding to the transistors with different features sizes and tunable by the gate bias. The spectrometer uses a symmetrical FET with interchangeable source and drain with the rectified THz voltage between the source and drain being proportional to the sine of the phase shift between the voltages induced by the THz signal between gate-to…
We report on room temperature THz detection by means of antenna-coupled field effect transistors fabricated by using epitaxial graphene grown on silicon carbide substrate. Two independent detection mechanisms are found: plasma wave assisted-detection and thermoelectric effect, which is ascribed to the presence of junctions along the FET channel. The superposition of the calculated functional dependence of both the plasmonic and thermoelectric photovoltages on the gate bias qualitatively well reproduces the measured photovoltages. Additionally, the sign reversal of the measured photovoltage dem…
The efficiency of photo-conductive switches, which continue to be used for the generation and detection of THz waves, has been overlooked for a long time. The so far 'optics-dominated' devices are making their way through to new and emerging fields of research that require ultrafast picosecond voltage pulses, as well as to new applications where power efficiency is of uttermost importance. To address the efficiency problems, in this article we present a novel photo-conductive switch that is based on a 3-dimensional design. In contrast to conventional planar designs, our photo-conductive switch…
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 t…
In this work, a plasmonic right-angled waveguide bend and divider are proposed. Using the Transformation Optics (TO) approach the transformation media of a bend and a T-shaped divider are obtained. Such media with continuous refractive index are realized with the help of graphene in the terahertz frequency range, key to effectively guiding the surface plasmon polariton (SPP) propagation on the 90 degree curves. Components with such capability are promising for THz device applications.
Highly integrated active nanophotonics addressing both device footprint and operation speed demands is a key enabling technology for the next generation optical networks. Plasmonic systems have proven to be a serious contender to alleviate current performance limitations in electro-optic devices. Here, we demonstrate a plasmonic optical phased array (OPA) consisting of two 10-$μ$m-long plasmonic phase shifters, utilized to control the far-field radiation pattern of two subwavelength-separated emitters for aliasing-free beam steering with an angular range of $\pm5^\circ$ and flat frequency resp…
This paper presents an efficient approach for exciting a dielectric resonator antenna (DRA) in the terahertz frequencies by means of a graphene plasmonic dipole. Design and analysis are performed in two steps. First, the propagation properties of hybrid plasmonic onedimensional and two-dimensional structures are obtained by using transfer matrix theory and the finite-element method. The coupling amount between the plasmonic graphene mode and the dielectric wave mode is explored based on different parameters. These results, together with DRA and plasmonic antenna theory, are then used to design…
This paper investigates tunable magneto-plasmons in graphene-based structures combined with gyro-electric layers. In the general waveguide, each graphene sheet has been sandwiched between two different gyro-electric layers. The whole structure has been exposed in the presence of a magnetic bias. An accurate analytical model based on all propagating modes has been proposed and led to closed-form complicated relations. As a special case of the multi-layer waveguide, a hybrid graphene-gyroelectric structure is studied in this paper. It has been illustrated that the propagating features of the exe…
In this paper, we analytically study Surface Plasmon Polaritons (SPPs) in graphene-based cylindrical structures with gyroelectric layers. In the general waveguide, each graphene layer is surrounded by two various gyro-electric materials. New closed-form relations are derived for the field contributions of SPP waves. As a special case, a gyro-electric cylindrical waveguide with double-layer graphene is considered in this article. For the designed structure, the figure of merit (FOM) of 51 is reported for B= 2 T and μc=0.7 eV, at the frequency of 33 THz. It is demonstrated that the FOM of the st…
Acoustic vibrations at the nanoscale (GHz-THz frequencies) and their interactions with electrons, photons and other excitations are the heart of an emerging field in physics: nanophononics. The design of ultrahigh frequency acoustic-phonon transducers, with tunable frequency, and easy to integrate in complex systems is still an open and challenging problem for the development of acoustic nanoscopies and phonon lasers. Here we show how an optimized plasmonic metasurface can act as a high-frequency phonon transducer. We report pump-probe experiments in metasurfaces composed of an array of gold n…
We propose a novel analytical model for anisotropic multi-layer cylindrical structures containing graphene layers. The general structure is formed by an aperiodic repetition of a three-layer sub-structure, where a graphene layer, with an isotropic surface conductivity, has been sandwiched between two adjacent magnetic materials. An external magnetic bias has been applied in the axial direction. General matrix representation is obtained in our proposed analytical model to find the dispersion relation. The relation will be used to find the effective index of the structure and its other propagati…
This paper aims to study the reflection characteristics of optical beams in a hybrid graphene-hexagonal Boron Nitride (hBN)-graphene structure, which has been located on SiO2-Si layers. An analytical model is presented to derive the reflection characteristics by using the transfer matrix method. The upper Reststrahlen band has been chosen as the studied frequency range. It is shown that the characteristics of the reflected beam can be effectively controlled by varying the chemical potential of graphene sheets. The obtained results represent a high value of the reflected group delay (=15.3 ps) …
This article proposes a novel three-port circulator with a triangular graphene-based post for the THz region. This new circulator is formed by three 120 symmetrical metal-based waveguides with a multi-layer triangular graphene-based post. The anisotropic feature for circulation is provided by magnetically-biased graphene in the triangular post. The DC magnetic bias is applied in the z-direction. The magnetized, triangular graphene sheet supports hybrid TM-TE plasmons. To realize the proposed circulator, the structure has been simulated in COMSOL software. In our simulation results, isolation o…
