- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Design of Bias-Free Operational Uni-traveling-Carrier Photodiodes by Transient Simulation for High-power Pulsed Millimeter-Wave Signal Generation in the Sub-THz Regime
摘要： In this paper, bias-free operational uni-traveling-carrier photodiodes (UTC-PDs) for high-power pulsed millimeter-wave signal generation in the sub-terahertz regime are designed and investigated. The reliability of the physics-based transient simulation is first demonstrated by comparing with reported experimental results. Then, the epitaxial layers are analyzed and optimized through transient simulation for bias-free operation and high-power pulsed millimeter-wave signal generation. The performance between original and optimal structure is compared under excitation of pulse train and sinusoidal optical signals. The results show that the peak output power of the modified UTC-PD under 100-GHz, 200-GHz, and 312.5-GHz pulse train excitation is 4.685 dBm, 1.128 dBm, and ? 4.653 dBm, improved by 2.05 dB, 5.15 dB, and 9.36 dB, respectively.
关键词： Bias-free,Optical communication,Millimeter-wave,Transient simulation,Terahertz communications,Sub-terahertz,Uni-traveling-carrier photodiodes (UTC-PD)
更新于2025-09-09 09:28:46
-
Super-Oscillatory Metalens at Terahertz for Enhanced Focusing with Reduced Side Lobes
摘要： In this paper, we design and numerically demonstrate an ultra-thin super-oscillatory metalens with a resolution below the diffraction limit. The zones of the lens are implemented using metasurface concepts with hexagonal unit cells. This way, the transparency and, hence, ef?ciency is optimized, compared to the conventional transparent–opaque zoning approach that introduces, inevitably, a high re?ection in the opaque regions. Furthermore, a novel two-step optimization technique, based on evolutionary algorithms, is developed to reduce the side lobes and boost the intensity at the focus. After the design process, we demonstrate that the metalens is able to generate a focal spot of 0.46λ0 (1.4 times below the resolution limit) at the design focal length of 10λ0 with reduced side lobes (the side lobe level being approximately ?11 dB). The metalens is optimized at 0.327 THz, and has been validated with numerical simulations.
关键词： metamaterials,evolutionary algorithm,metasurfaces,terahertz,metalens,terahertz focusing,subwavelength focusing,super-oscillatory lens
更新于2025-09-09 09:28:46
-
[IEEE 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz2018) - Nagoya, Japan (2018.9.9-2018.9.14)] 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Coherent control of femtosecond spin current investigated by polarization dependent terahertz emission spectroscopy in ferromagnetic heterostructures
摘要： Approaches towards highly-efficient generation of controllable ellipitical ferromagnetic nano-heterostructures are demonstrated. The mechanism for the coherent control of femtosecond spin current in ferromagnetic heterostructures are discussed.
关键词： coherent control,ferromagnetic heterostructures,terahertz emission spectroscopy,femtosecond spin current
更新于2025-09-09 09:28:46
-
[IEEE 2018 20th International Symposium on High-Current Electronics (ISHCE) - Tomsk, Russia (2018.9.16-2018.9.22)] 2018 20th International Symposium on High-Current Electronics (ISHCE) - Generation of Terahertz Radiation by Electron Beam-Plasma Interaction
摘要： At present, the search for new methods of generation electromagnetic radiation in the terahertz frequency range (THz) has emerged as one of the most promising rapidly in science and engineering, developing areas of research including security and medical diagnostics. One of the modern solutions of the problem is the generation of electromagnetic (EM) waves due to the interaction of high-current relativistic electron beams with plasma. Since in this case the radiation frequency is comparable with the plasma frequency, it can be easily adjusted by simply changing the plasma density. The efficient terahertz electromagnetic emission was produced during the injection of relativistic electron beams into plasma in laboratory experiments at the GOL-3 facility INP SB RAS. In this paper the mechanisms of the high efficiency of energy transfer from the relativistic electron beam to the EM radiation in turbulent regime of collisionless plasma are investigated on the base of computer simulation. The kinetic approach for ion and electron plasma components, as well as for electron beam, was used in 2D numerical model with the real mass ratio of charged particles. A parallel electromagnetic particle-in-cell (PIC) code UMKA2D3V was applied to simulate beam-plasma system for parameters close to the parameters of laboratory experiments at GOL-3 facility. Regimes of injection of one electron beam into the plasma and the counter injection of electron beams were considered. Computational experiments were performed using modern computer systems with massively parallel architecture.
关键词： terahertz radiation,electron beam-plasma interaction,PIC-method,plasma physics
更新于2025-09-09 09:28:46
-
Electrically tunable harmonics in time-modulated metasurfaces for wavefront engineering
摘要： Modulation of metasurfaces in time gives rise to several exotic space-time scattering phenomena by breaking the reciprocity constraint and generation of higher-order frequency harmonics. We introduce a new design paradigm for time-modulated metasurfaces, enabling tunable engineering of the generated frequency harmonics and their emerging wavefronts by electrically controlling the phase delay in modulation. It is demonstrated that the light acquires a dispersionless phase shift regardless of incident angle and polarization, upon undergoing frequency conversion in a time-modulated metasurface which is determined by the modulation phase delay and the order of generated frequency harmonic. The conversion efficiency to the frequency harmonics is independent of modulation phase delay and only depends on the modulation depth and resonant characteristics of the metasurface element, with the highest efficiency occurring in the vicinity of resonance, and decreasing away from the resonance. The modulation-induced phase shift allows for creating tunable spatially varying phase discontinuities with 2π span at the generated frequency harmonics for a wide range of frequencies and incident angles. Specifically, we apply this approach to a time-modulated metasurface in the Terahertz regime consisted of graphene-wrapped silicon microwires. For this purpose, we use an accurate and efficient semi-analytical framework based on multipole scattering. We demonstrate the utility of the design rule for tunable beam steering and focusing of generated frequency harmonics, giving rise to several intriguing effects such as spatial decomposition of harmonics, anomalous bending with full coverage of angles and dual-polarity lensing. Furthermore, we investigate the angular and spectral performance of the time-modulated metasurface in manipulation of generated frequency harmonics to verify its constant phase response versus incident wavelength and angle. The nonreciprocal response of the metasurface in wavefront engineering is also studied by establishing nonreciprocal links via modulation-induced phase shift. The proposed design approach enables a new class of high-efficiency tunable metasurfaces with wide angular and frequency bandwidth, wavefront engineering capabilities, nonreciprocal response and multi-functionality.
关键词： Terahertz,wavefront engineering,nonreciprocal response,graphene,time-modulation,metasurfaces
更新于2025-09-09 09:28:46
-
Photoconductive antennas based on epitaxial films In <sub/>0.5</sub> Ga <sub/>0.5</sub> As on GaAs (1?1?1)A and (1?0?0)A substrates with a metamorphic buffer
摘要： The terahertz (THz) wave generation by the spiral photoconductive antennas fabricated on the low-temperature and high-temperature grown undoped and Si-doped In0.5Ga0.5As films is studied by the terahertz time-domain spectroscopy method. The In0.5Ga0.5As layers were grown by molecular beam epitaxy on GaAs substrates with (1 0 0) and (1 1 1) A crystallographic orientations utilizing step-graded InxGa1?xAs metamorphic buffer. The antennas are excited by radiation of Er3+-fiber laser at 1.56 μm wavelength in two regimes: with pulse durations of 2.5 ps or 100 fs. It is found that the THz wave generation is 3–4 times more effective in the case of InGaAs-based antennas on (1 1 1)A GaAs substrates as compared to the (1 0 0) substrates. Power-voltage characteristic of the LT-InGaAs antenna up to and beyond threshold breakdown voltage are reported.
关键词： time-domain spectroscopy,terahertz wave generation,photoconductive antenna,GaAs (1 1 1)A,InGaAs,molecular beam epitaxy
更新于2025-09-09 09:28:46
-
THz Sensing With Anomalous Extraordinary Optical Transmission Hole Arrays
摘要： Subwavelength hole array (HA) metasurfaces support the so-called extraordinary optical transmission (EOT) resonance that has already been exploited for sensing. In this work, we demonstrate the superior performance of a different resonant regime of HA metasurfaces called anomalous EOT, by doing a thorough numerical and experimental study of its ability in thin-film label-free sensing applications in the terahertz (THz) band. A comprehensive analysis using both the regular and anomalous EOT resonances is done by depositing thin layers of dielectric analyte slabs of different thicknesses on the structures in different scenarios. We carry out a detailed comparison and demonstrate that the best sensing performance is achieved when the structure operates in the anomalous EOT resonance and the analyte is deposited on the non-patterned side of the metasurface, improving by a factor between 2 and 3 the results of the EOT resonance in any of the considered scenarios. This can be explained by the comparatively narrower linewidth of the anomalous EOT resonance. The results presented expand the reach of subwavelength HAs for sensing applications by considering the anomalous EOT regime that is usually overlooked in the literature.
关键词： metasurface,thin film,anomalous EOT,sensing,terahertz
更新于2025-09-09 09:28:46
-
Terahertz two-pixel imaging based on complementary compressive sensing
摘要： A compact terahertz (THz) imaging system based on complementary compressive sensing has been proposed using two single-pixel detectors. By using a mechanical spatial light modulator, sampling in the transmission and re?ection orientations was achieved simultaneously, which allows imaging with negative mask values. The improvement of THz image quality and anti-noise performance has been veri?ed experimentally compared with the traditional reconstructed image, and is in good agreement with the numerical simulation. The demonstrated imaging system, with the advantages of high imaging quality and strong anti-noise property, opens up possibilities for new applications in the THz region.
关键词： image reconstruction techniques,terahertz imaging,spatial light modulators
更新于2025-09-09 09:28:46
-
A 128-Pixel System-on-a-Chip for Real-Time Super-Resolution Terahertz Near-Field Imaging
摘要： This paper presents a fully integrated system-on-a-chip for real-time terahertz super-resolution near-field imaging. The chip consists of 128 sensing pixels with individual cross-bridged double 3-D split-ring resonators arranged in a 3.2 mm long 2 × 64 1-D array. It is implemented in 0.13-μm SiGe bipolar complementary metal–oxide–semiconductor technology and operated at around 550 GHz. All the functions, including sensor illumination, near-field sensing, and detection, are co-integrated with a readout integrated circuit for real-time image acquisition. The pixels exhibit a permittivity-based imaging contrast with a worst case estimated relative permittivity uncertainty of 0.33 and 10–12-μm spatial resolution. The sensor illumination is provided with on-chip oscillators feeding four-way equal power divider networks to enable an effective pixel pitch of 25 μm and a dense fill factor of 48% for the 1-D sensing area. The oscillators are equipped with electronic chopping to avoid 1/f-noise-related desensitization for the SiGe-heterojunction bipolar transistor power detectors integrated at each pixel. The chip features both an analog readout mode and a lock-in-amplifier-based digital readout mode. In the analog readout mode, the measured dynamic range (DR) is 63.8 dB for a 1-ms integration time at an external lock-in amplifier. The digital readout mode achieves a DR of 38.5 dB at 28 f/s. The chip consumes 37–104 mW of power and is packaged into a compact imaging module. This paper further demonstrates real-time acquisition of 2-D terahertz super-resolution images of a nickel mesh with 50-μm feature size, as well as a biometric human fingerprint.
关键词： terahertz,system-on-a-chip (SoC),SiGe heterojunction bipolar transistor (HBT),split-ring resonator (SRR),near-field array,3-push Colpitts oscillator,super-resolution imaging,near-field scanning optical microscopy (NSOM),power detector
更新于2025-09-09 09:28:46
-
[IEEE 2018 IEEE International Conference on Information Communication and Signal Processing (ICICSP) - Singapore, Singapore (2018.9.28-2018.9.30)] 2018 IEEE International Conference on Information Communication and Signal Processing (ICICSP) - A Load-Aware Dynamic TDMA Protocol for Terahertz Wireless NanoSensor Networks
摘要： Wireless NanoSensor Networks (WNSNs) is a new type of networks which combines nanotechnology and sensor networks, having promising applications in the biomedical, industrial, environmental and military fields. Due to the peculiarities of WNSNs, such as molecular absorption noise in the Terahertz channel and the limited capacities of nano-nodes, novel Medium Access Control (MAC) protocols are needed to regulate access to the channel and coordinate transmission orders among nano-nodes. In this paper, a load-aware dynamic TDMA (LAD-TDMA) protocol is proposed. This protocol is built on a novel pulsed-based communication scheme called TS-OOK and avoids symbol collisions to achieve high energy efficiency. LAD-TDMA adopts a dynamic TDMA- based time slot allocation mechanism according to the current number and corresponding traffic of source nodes, the channel. The transmission peculiarities of Terahertz performance of the protocol is evaluated and analyzed in terms of energy consumption, average end-to-end delay and average throughput, by using the NS3 simulation platform. Results show that LAD-TDMA is energy efficient and advantageous in average end-to-end delay and average throughput, which is proved to be suitable to support node-intensive and load- unbalanced WNSNs, by considering the properties of Terahertz band, energy limitation of nano-devices and nano- nodes’ traffic.
关键词： Terahertz,WNSNs,TS-OOK,TDMA,load-aware
更新于2025-09-09 09:28:46