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Wideband Rectangular Double-Ring Nanoribbon Graphene-Based Antenna for Terahertz Communications
摘要： A wideband nanoribbon graphene-based antenna with double rectangular rings for terahertz (THz) applications is presented. The wideband and efficient graphene-based antenna on physical parameters is developed in this paper. The antenna has a wide impedance bandwidth of 26% at the center frequency of 1 THz, minimum return loss equal to 24 dB and average radiation efficiency approximately equal to 44% is obtained. An average gain of 2.45 dB is achieved at the operational frequency band. The goal of this paper is to provide an antenna with capabilities of being wideband, efficient and re-configurable with a simple and single-layer structure for THz communication.
关键词： Double-ring antenna,wideband antenna,graphene,terahertz,THz,re-con?gurable,nanoribbon antenna
更新于2025-09-11 14:15:04
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[IEEE 2019 IEEE/MTT-S International Microwave Symposium - IMS 2019 - Boston, MA, USA (2019.6.2-2019.6.7)] 2019 IEEE MTT-S International Microwave Symposium (IMS) - Silicon-Micromachined Waveguide Calibration Shims for Terahertz Frequencies
摘要： A new method of realising precision waveguide shims for use in THz Through-Re?ect-Line (TRL) calibrations, based on silicon-micromachining, is introduced. The proposed calibration shims combine a thin λ/4 silicon layer, co-fabricated with a thicker layer which provides mechanical support. This design overcomes the limitations of CNC milling for the creation of calibration shims, facilitating use of standard TRL calibration at currently challenging frequencies. The novel shim ?ts inside the inner recess of a standard waveguide ?ange and is compatible with conventional ?ange alignment pins. Five micromachined shims were fabricated in a silicon-on-insulator process for operation in the WM-570 waveguide band (325 – 500 GHz). The fabricated shims show excellent performance across the entire band, with return loss in excess of 25 dB, insertion loss below 0.2 dB and high uniformity between samples. Veri?cation reveals that the micromachined shims have an electrical length within 2% of the expected value. Comparative measurements of a DUT calibrated with the proposed shim and a previously un-used conventional metallic shim show that the novel concept offers equivalent, if not better, performance. The mechanical design of the micromachined shim and the rigid nature of silicon ensure that it will not suffer from performance degradation with repeated use, as is problematic with thin metallic shims. This work enables the creation of low-cost, highly-repeatable, trace- able calibration shims with micrometer feature-sizes and high product uniformity, surpassing the limits of current techniques.
关键词： calibration,micromachining,TRL,terahertz,waveguide,THz
更新于2025-09-11 14:15:04
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A Hybrid THz Imaging System With a 100-Pixel CMOS Imager and a 3.25–3.50 THz Quantum Cascade Laser Frequency Comb
摘要： The terahertz frequency range beyond 3 THz has exciting potential to have a transformative impact in a wide range of applications, including chemical and biomedical sensing, spectroscopy, imaging, and short-distance wireless communication. While there have been significant advancements in silicon-based THz imagers in the frequency ranges below 1 THz, technological development beyond 3 THz has been impeded by the lack of solid-state sources in this frequency range. In addition, the design space beyond 3 THz opens up fundamentally new challenges across electronics and the electromagnetic interface. In this spectral range, the wavelength is small enough (λox ≈ 50 μm at 3 THz) that a vertical via from the top antenna layer to the detector is a distributed element (transmission line or radiator). In this letter, we follow a careful circuits-electromagnetics co-design approach toward a hybrid imaging system with a 100-pixel CMOS imager that interfaces with a THz quantum cascade laser frequency comb that spans 3.25–3.5 THz with mode spacing of 17 GHz. The array chip, while designed for an optimal operation across 2.7–2.9 THz, demonstrates an average noise equivalent power (NEP) (across pixels) of 1260 pW/√Hz between 3.25–3.5 THz and a projected NEP of 284 pW/√Hz across the design range of 2.7–2.9 THz. To the best of our knowledge, we demonstrate for the first time full THz imaging in a hybrid quantum cascade laser (QCL)–CMOS fashion. This approach allows future works to leverage both QCL and CMOS technologies to demonstrate new technological advances for systems in the 1–10 THz range.
关键词： hybrid imaging,quantum cascade laser,silicon,THz imaging,CMOS,terahertz,imaging,detector
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - N-Type Ge/SiGe Quantum Cascade Heterostructures for THz Emission
摘要： Terahertz (THz) semiconductor based quantum cascade lasers (QCLs) represent powerful and compact integrated light sources. To date they have been realized with various III-V materials where LO phonon emission becomes very effective as the temperature is increased, limiting the maximum operating temperature to 200K. To overcome this limitation, non-polar material systems are attractive because of their weaker e-phonon interaction. Theoretical studies have indicated n-type Ge/SiGe heterostructures where transport is associated to L electrons, as the most promising architecture [1]. Experimentally, sharp intersubband transitions in n-type strain compensated Ge/SiGe QWs have been observed in the 20-50 meV region [2]. Recently, non-equilibrium Green’s functions calculations proved to be efficient in optimising high temperature performance of GaAs/AlGaAs THZ QCLs [3]. In the effort of realizing a Ge/SiGe THz QCL, we present here a QCL structure designed by means of non-equilibrium Green’s functions [4], whose the bandstructure is reported in Fig.1(a). Epitaxial growth of strain-compensated Ge/SiGe heterostructure (≈1.5 μm thick) has been carried out by means of UHV-CVD yielding very good sample quality as visible from Fig.1(b). Mesa devices for transport experiments have been fabricated by dry etching and metallization. In Fig.1(c) a series of I-V curves as a function of the heatsink temperature display a thermally activated behaviour with Eact (cid:3) 10 meV. From low temperature (4 K) magnetotransport [5] in a magnetic field parallel to the current direction shows characteristics oscillations. we can deduce an energy distance between the lasing states of E23 =19.5 meV, in good agreement with the theoretical calculation. Optical experiments are ongoing and experimental results will be presented.
关键词： THz,UHV-CVD,quantum cascade lasers,Ge/SiGe heterostructures,non-equilibrium Green’s functions
更新于2025-09-11 14:15:04
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[IEEE 2019 5th Conference on Knowledge Based Engineering and Innovation (KBEI) - Tehran, Iran (2019.2.28-2019.3.1)] 2019 5th Conference on Knowledge Based Engineering and Innovation (KBEI) - A Triple-Band THz Metamaterial Absorber Based on Symmetrical Split Rings
摘要： A simple pattern of a triple band terahertz (THz) absorber is presented. This absorber formed by only triple symmetrical split rings backed with a solid ground layer which is separated by a dielectric layer substrate. It is investigated that the presented absorber has three different absorption bands in which the average of the peaks is close to 96%. Results reveal that the absorption bandwidth of the presented design is insensitive to wave incident angle. In addition, in order to enhance the absorption peaks, a new method is introduced which is based on the difference of split rings thickness. Owing to the simple structure of the proposed absorber, the fabrication process can be quite easy. Therefore, the proposed THz absorber is able to perform in applications such as sensing, detection, and imaging.
关键词： split rings structure,metamaterial,triple band,terahertz (THz),absorber
更新于2025-09-11 14:15:04
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - THz excited state level spacing in encapsulated graphene quantum dots
摘要： We report a high-quality encapsulated graphene quantum dot that exhibits stable Coulomb diamonds and excited states with a spacing of 0.4 THz. We performed the first transport spectroscopy measurement under THz illumination of a large quantum dot. The photocurrent map allows to measure with high precision a non-linear chemical potential renormalization of the graphene electrodes via the interaction with the quantum dot states.
关键词： graphene quantum dots,THz,transport spectroscopy,chemical potential renormalization,photocurrent
更新于2025-09-11 14:15:04
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[IEEE 2019 21st International Conference on Transparent Optical Networks (ICTON) - Angers, France (2019.7.9-2019.7.13)] 2019 21st International Conference on Transparent Optical Networks (ICTON) - Materials for Nonlinear Optics in the GHz-THz Range
摘要： This talk starts with an outline of our hybrid approach combining Nonequilibrium Green's Functions with the Boltzmann equation for the nonlinear response of semiconductor superlattices. The nonlinearities are controllable and very good agreement has been found between theory and experiments. Next, we address the efficiency of the superlattices as frequency multipliers and their feasibility for room temperature THz radiation sources based on multiplication of GHz inputs.
关键词： semiconductor superlattices,THz,Boltzmann equations,GHz,nonequilibrium Green’s functions,frequency multiplication
更新于2025-09-11 14:15:04
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n-type Ge/SiGe Multi Quantum-Wells for a THz Quantum Cascade Laser
摘要： Exploiting intersubband transitions in Ge/SiGe quantum cascade devices provides a way to integrate terahertz light emitters into silicon-based technology. With the view to realizing a Ge/SiGe Quantum Cascade Laser, we present the optical and structural properties of n-type strain-symmetrized Ge/SiGe asymmetric coupled quantum wells grown on Si(001) substrates by means of ultrahigh vacuum chemical vapor deposition. We demonstrate high material quality of strain-symmetrized structures and heterointerfaces as well as control over inter-well coupling and electron tunneling. Motivated by the promising results obtained on ACQWs, which are the basic building block of a cascade structure, we investigate, both experimentally and theoretically, a Ge/SiGe THz QCL design, optimized through a non-equilibrium Green’s function formalism.
关键词： Ge/SiGe,THz,intersubband transitions,strain-symmetrized,Quantum Cascade Laser
更新于2025-09-11 14:15:04
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[IEEE 2019 IEEE MTT-S International Microwave Workshop Series on Advanced Materials and Processes for RF and THz Applications (IMWS-AMP) - Bochum, Germany (2019.7.16-2019.7.18)] 2019 IEEE MTT-S International Microwave Workshop Series on Advanced Materials and Processes for RF and THz Applications (IMWS-AMP) - Experimental Investigation of Terahertz Wave Scattering by Statistically Controlled Rough Surfaces
摘要： In this work, the experimental investigation of electromagnetic wave scattering by statistically controlled rough surfaces in the lower THz band is demonstrated. Rough surfaces with height fluctuations following normal statistics are fabricated using two different 3D printing techniques. The results presented here confirm that the surface roughness has a noticeable effect on the level of the diffuse scattering energy. In the future, the applied method can be used to validate analytical models as well as to gain scattering patterns from more complicated rough surface structures which fall outside the limits of most analytical approximations.
关键词： scattering measurements,statistically controlled rough surfaces,THz communication
更新于2025-09-11 14:15:04
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - High Performance Graphene Ballistic Rectifiers for THz detection
摘要： Although graphene can operate in the ballistic transport regime at room temperature, there are very few devices harnessing this property. Here we present a novel device called the ballistic rectifier which circumvents the problem of opening a bandgap in graphene. Based on the device theory, we propose four different asymmetric planar structures. All devices are working and show responsivity higher than 1,000 V/W at room temperature, with noise-equivalent power as low as 4.16 pW/Hz1/2. These properties make GBRs a suitable candidate for THz detection.
关键词： THz detection,noise-equivalent power,ballistic rectifier,responsivity,graphene
更新于2025-09-11 14:15:04