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[IEEE ESSCIRC 2019 - IEEE 45th European Solid State Circuits Conference (ESSCIRC) - Cracow, Poland (2019.9.23-2019.9.26)] ESSCIRC 2019 - IEEE 45th European Solid State Circuits Conference (ESSCIRC) - A Hybrid THz Imaging System With a 100-Pixel CMOS Imager and a 3.25a??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： quantum cascade laser,THz imaging,terahertz,detector,imaging,CMOS,silicon,hybrid imaging
更新于2025-09-23 15:19:57
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Low-Loss and Dispersion-Flattened Octagonal Porous Core PCF for Terahertz Transmission Applications
摘要： In order to make the direct transmission more effective, we have intended an octagonal shape cladding design in this paper. The minimum resultant effective material loss obtained from our proposed photonic crystal fiber is 0.007 cm-1 at 0.5 THz is very effective. The proposed design gives an ultra-high birefringence of 0.06 with an effective area of about 4 9 10-6 m2, a core power fraction of 70% for 290 lm core diameter with a core porosity of 80% at 1.6 THz frequency and closely zero flattened dispersion of variation of 0.3 ± 0.1 ps/THz/cm at a wide frequency range of 0.7–2.1 THz.
关键词： Terahertz,Core porosity,Effective material loss,Octagonal core,Confinement loss,Dispersion
更新于2025-09-23 15:19:57
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Investigation of GaAsBi epitaxial layers for THz emitters pumped by long-wavelength fiber lasers
摘要： Herein we report the studies on the GaBiAs terahertz emitters. The molecular beam epitaxy grown thin films were subjected to structural and optical characterization. Inhomogeneity of Bi concentration in the samples is confirmed by XRD, PL and EDS studies. Investigations on the generation characteristics of the fabricated bow-tie photoconductive antennas were carried out via the Fourier Transform Infrared Spectroscopy. The collected data indicate a pattern of change in the shape of the spectra with increasing bismuth concentration, namely, a sharp drop in the low-frequency part (0.1–0.2 THz) simultaneously with a noticeable increase in intensity in the range 0.3–1 THz with a pronounced maximum at frequencies of ~0.4 THz. The deterioration of the THz power to average photocurrent ratio can be explained by a general decrease in the electron mobility, caused both by a large number of structural defects and by a large local heating of the crystal.
关键词： terahertz emitters,photoconductive antennas,molecular beam epitaxy,GaBiAs,Fourier Transform Infrared Spectroscopy
更新于2025-09-23 15:19:57
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Smaller antenna-gate gap for higher sensitivity of GaN/AlGaN HEMT terahertz detectors
摘要： We report an attempt to improve the sensitivity of terahertz detection based on self-mixing in antenna-coupled ?eld-effect transistors by enhancing the ?eld-effect factor and the antenna factor with a reduced gate length and a reduced antenna-gate gap, respectively. An optical noise equivalent power (NEP) of 3:7 pW= ??????Hz at 0.65 THz was achieved in a GaN/AlGaN high-electron-mobility transistor (HEMT) with a gate length of 300 nm and an antenna-gate gap of 200 nm at room temperature. It was found that the antenna factor was inversely proportional to the antenna-gate gap, and the responses upon coherent/incoherent terahertz irradiation were well described by the self-mixing model. To ?ll the NEP gap of 0:1 (cid:2) 1 pW= ??????Hz between room-temperature and cryogenic detectors by HEMT-based detectors at room temperature, impedance match needs to be carefully considered.
关键词： terahertz detection,GaN/AlGaN HEMT,self-mixing,field-effect transistors,antenna-coupled
更新于2025-09-23 15:19:57
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A 38 dBi Gain, Low-Loss, Flat Array Antenna for 320 GHz to 400 GHz Enabled by Silicon-On-Insulator Micromachining
摘要： Two high-gain ?at array antenna designs operating in the 320 – 400 GHz frequency range are reported in this paper. The two antennas show measured gains of 32.8 dBi and 38 dBi and consist of a 16 × 16 (256) element array and a 32 × 32 (1024) element array, respectively, which are fed by a corporate H-tree beamforming network. The measured operation bandwidth for both antennas is 80 GHz (22 % fractional bandwidth), and the total measured ef?ciency is above ?2.5 dB and above ?3.5 dB for the two designs in the whole bandwidth. The low measured loss and large bandwidth are enabled by optimizing the designs to the process requirements of the SOI micromachining technology used in this work. The total height of the antennas is 1.1 mm (1.2 λ at the center frequency), with sizes of 15 mm × 18 mm and 27 mm × 30 mm for both arrays. The antennas are designed to be directly mounted onto a standard WM-570 waveguide ?ange. The design, fabrication, and measurements of eight prototypes are discussed in this paper and the performance of the antennas compared to the simulated data, as well as manufacturability and fabrication repeatability are reported in detail.
关键词： terahertz radiation,corporate beamforming network,array antennas,silicon micromachining,silicon on insulator,waveguide arrays,submillimeter-wave antennas
更新于2025-09-23 15:19:57
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Nanoplasma-enabled picosecond switches for ultrafast electronics
摘要： The broad applications of ultrawide-band signals and terahertz waves in quantum measurements, imaging and sensing techniques, advanced biological treatments, and very-high-data-rate communications have drawn extensive attention to ultrafast electronics. In such applications, high-speed operation of electronic switches is challenging, especially when high-amplitude output signals are required. For instance, although field-effect and bipolar junction devices have good controllability and robust performance, their relatively large output capacitance with respect to their ON-state current substantially limits their switching speed. Here we demonstrate a novel on-chip, all-electronic device based on a nanoscale plasma (nanoplasma) that enables picosecond switching of electric signals with a wide range of power levels. The very high electric field in the small volume of the nanoplasma leads to ultrafast electron transfer, resulting in extremely short time responses. We achieved an ultrafast switching speed, higher than 10 volts per picosecond, which is about two orders of magnitude larger than that of field-effect transistors and more than ten times faster than that of conventional electronic switches. We measured extremely short rise times down to five picoseconds, which were limited by the employed measurement set-up. By integrating these devices with dipole antennas, high-power terahertz signals with a power–frequency trade-off of 600 milliwatts terahertz squared were emitted, much greater than that achieved by the state of the art in compact solid-state electronics. The ease of integration and the compactness of the nanoplasma switches could enable their implementation in several fields, such as imaging, sensing, communications and biomedical applications.
关键词： picosecond switches,terahertz waves,ultrafast electronics,nanoplasma,electronic switches
更新于2025-09-23 15:19:57
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A switchable terahertz reflectarray consisting of crossed metal dipoles set in a graphene grid
摘要： A switchable reflectarray antenna composed of crossed metal dipoles mounted on a graphene grid is proposed for switchable radiation patterns at 1 THz. For an individual radiating element, the single graphene square loop works together with the metal dipoles to offer a corresponding phase response. As an entirety, the grid formed by the attached graphene loops is connected to a particular bias electrode for switchable operation. Taking the practical manufacturing technique into account, the graphene-oxide-silicon structure is used as the bias electrode. The simulated phase response shows that a phase range over 330○ is obtained by changing the dimension of the metal dipoles from 11 μm to 70 μm. The simulated field distributions and radiation patterns demonstrate that the proposed structure can deflect the normal incident plane waves in the predesigned direction when it is biased in a specific state. Once the bias is set to zero, incident plane waves are scattered into different directions.
关键词： radiation patterns,terahertz,metal dipoles,graphene grid,switchable reflectarray
更新于2025-09-23 15:19:57
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A multimode graphene plasmonic perfect absorber at terahertz frequencies
摘要： Graphene, a new smart material, has attracted remarkable attention in recent years owing to its tunable band structure and strong light–matter interaction. Compared to typical absorber, graphene absorber is recently considered as a highly promising candidate for multi-mode purpose. Here, a new tunable hexagonal-shape graphene-based THz absorber is proposed. To achieve nearly perfect broadband terahertz absorption, six layers of graphene is utilized. By introducing such a unique gradient, the continuous plasmon resonances of the absorber can be directly excited and broadband terahertz absorption can be achieved. Additionally, contrary to conventional absorbers which often neglect the high-order modes, particularly in THz regime, the proposed absorber has the advantage of achieving unit absorbance peak not only for the first resonance mode, but for higher order modes. To validate the sensitivity of the proposed absorber, frequency sensitivity and amplitude sensitivity are calculated. The highest frequency sensitivity is achieved 15.3012 for the second mode at ?? = 60? and the highest amplitude sensitivity is estimated to be 45.1482 for the fourth mode at the same incident angle.
关键词： Plasmonics,Terahertz,Graphene,Multi-mode absorber
更新于2025-09-23 15:19:57
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A flexible and ultra-broadband terahertz wave absorber based on graphenea??vertically aligned carbon nanotube hybrids
摘要： Electromagnetic wave absorbers are essential devices in imaging, wireless communication and energy harvesting systems. In this paper, we propose and experimentally demonstrate a flexible and ultra-broadband terahertz (THz) wave absorber based on graphene-vertically aligned carbon nanotube (G-VACNT) hybrids. The THz absorber consists of Cu/PDMS/graphene/VACNT functional layers on PET substrate. Measured results show a 100% qualified operating bandwidth (i.e., absorptance >0.9) and an average power absorptance of 0.986 within the 0.2-3.0 THz range. The absorber also exhibits good absorption performances for a wide range of incident angles up to 60°, and can function normally in different bending states due to its excellent flexibility. The incoming energy of THz waves absorbed by the G-VACNT hybrids results in a temperature increase whose spatial distribution is corresponding to the profile of incident THz beam, providing an efficient and low cost approach for THz beam profiling, collimation and focusing. This work paves the way for the development of large-scale and broadband THz wave absorbers.
关键词： Vertically aligned carbon nanotube,Ultra-broadband,Graphene,Flexible,Terahertz wave absorber
更新于2025-09-23 15:19:57
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An antipodal Vivaldi antenna for improved far-field properties and polarization manipulation of broadband terahertz quantum cascade lasers
摘要： We present an antipodal Vivaldi antenna for broadband double metal waveguide terahertz quantum cascade lasers and frequency combs. Its exponentially curved flare profile results in an adiabatic in-plane mode expansion, producing an improved far-field with a single-lobed beam of (23° × 19°) full width half maximum with an octave-spanning bandwidth. The antenna also acts as a wave retarder, rotating the polarization from vertical toward horizontal polarization by a frequency-dependent angle. The laser’s emission spectrum and current–voltage characteristics are not affected, as well as frequency comb operation. Measurements agree well with numerical simulations, and the proposed antenna covers a broad spectral range (1.5–4.5 THz).
关键词： antipodal Vivaldi antenna,broadband,polarization manipulation,far-field properties,terahertz quantum cascade lasers
更新于2025-09-23 15:19:57