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Contents: (Adv. Funct. Mater. 48/2018)
摘要： New organic three-component single crystals exhibiting large macroscopic optical nonlinearity, excellent optical quality, and efficient optical-to-THz conversion are developed using so-called 'pseudo-isomorphic cocrystallization' for nonlinear optical and THz photonic applications.
关键词： THz photonics,pseudo-isomorphic cocrystallization,organic single crystals,nonlinear optics
更新于2025-09-09 09:28:46
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[IEEE 2018 IEEE Asia-Pacific Conference on Antennas and Propagation (APCAP) - Auckland, New Zealand (2018.8.5-2018.8.8)] 2018 IEEE Asia-Pacific Conference on Antennas and Propagation (APCAP) - Influence Analysis of ZrO<inf>2</inf> Ceramic for Cellular Phones on 5G mm-Wave Antenna Performance
摘要： In this paper, the influences of ZrO2 ceramic on the fifth generation mobile communications (5G) millimeter-wave (mm-Wave) antenna performance are studied. A 28-GHz 2 × 2 non-stacked patch antenna array and a 28-GHz 2 × 2 stacked patch antenna array are designed on dielectric substrates as the performance baseline. Based on the two types of antenna arrays, various ZrO2 ceramic thicknesses and various gaps between the ZrO2 ceramic and the antenna arrays are simulated to get quick understanding of the ZrO2 ceramic influence on the antenna performance. From the simulated results, it can be found that the ZrO2 ceramic has different influences on different types of antenna arrays. Besides, for both of the two types of antenna arrays, when the thicknesses of ZrO2 ceramic are close or equal to integer multiples of 0.5 guided wavelengths ((cid:540)g), the antenna performance in the material-loading cases gets close to that in the free space (FS). Also, when the thicknesses of ZrO2 ceramic are close or equal to odd multiples of 0.25 (cid:540)g and the gaps between the ZrO2 ceramic and the antenna array are close or equal to integer multiples 0.5 FS wavelengths ((cid:540)0), the focusing effects of electromagnetic (EM) beams get significant for both arrays. The findings comply with the EM wave propagation theory and can be applied to radome designs of Terahertz (THz) antenna arrays.
关键词： 5G,mm-Wave,ZrO2,THz,ceramic,antenna
更新于2025-09-09 09:28:46
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[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) - Terahertz (THz) Direct Detectors based on Superconducting HEBs with Thermal, Microwave and THz Biasing
摘要： Terahertz (THz) direct detectors based on superconducting niobium nitride (NbN) hot electron bolometers (HEBs) with thermal, microwave (MW) and THz biasing have been studied at 0.65 THz and 4.2 K in detail. The current responsivity and noise equivalent power (NEP) have been measured and compared respectively. The detectors with the MW and THz biasing have about one order higher current responsivity than that of the thermal one. With the MW biasing, an NEP at the order of pW/√Hz is obtained by choosing the MW frequency and power appropriately.
关键词： Terahertz,direct detectors,microwave biasing,niobium nitride,current responsivity,hot electron bolometers,superconducting,THz biasing,thermal biasing,noise equivalent power
更新于2025-09-09 09:28:46
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[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) - Optical Rectification of a 100W Average Power Ultrafast Thin-Disk Oscillator
摘要： We demonstrate THz generation by optical rectification in GaP crystals using excitation average power levels exceeding 100 W. The laser source is a state-of-the-art diode-pumped Yb:YAG modelocked thin-disk laser, capable of generating 120 W at 13.4 MHz directly from a one-box oscillator, without the need for any amplification stages. In this first demonstration, we measured a maximum average power of 78 μW at a central frequency of 0.8 THz. This first result shows that optical rectification of high average power (100 W class) ultrafast sources is within reach, and paves the way towards Watt-level, ultrafast laser pumped THz sources.
关键词： optical rectification,ultrafast lasers,GaP crystals,high average power,THz generation
更新于2025-09-09 09:28:46
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[IEEE 2018 14th IEEE International Conference on Solid-State and Integrated Circuit Technology (ICSICT) - Qingdao, China (2018.10.31-2018.11.3)] 2018 14th IEEE International Conference on Solid-State and Integrated Circuit Technology (ICSICT) - Emerging Terahertz Technologies for Security, Quality Control, Vision and Medical Applications
摘要： The spectrum of electromagnetic radiation covers a broad range of frequencies, spanning from micro-, millimeter- and radiowaves from one side to visible, ultraviolet and X-ray bands on the other. Nowadays, both these spectral ends are effectively explored in a multitude of devices and applications. In contrast, the intermediate zone, grouping electromagnetic waves of frequencies from 100 GHz to 10 THz, remains largely unexplored, lending itself a name of 'THz gap'. A very useful property of THz radiation is that it easily penetrates through most of non-metallic materials, at the same time providing spectroscopic information for matter classification. It allows to investigate internal structure or content of objects. Also, unlike UV or X-ray, THz waves are non-ionizing and hence harmless to humans and animals, eliminating the need for safety measures.
关键词： Terahertz,non-ionizing,THz gap,electromagnetic spectrum,spectroscopy
更新于2025-09-09 09:28:46
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[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) - Bi-layer Metamaterial based Broadband Linear Polarization Converter under Two Coherent Beam Illumination
摘要： We demonstrate a bi-layer metamaterial structure with mirror symmetry that acts as a linear polarization converter under two-antisymmetric-beam illumination. Its high performance, including broad bandwidth, high transmittance and high efficiency, originates from the combination of two interference processes: the Fabry-Pérot-like cavity effect between two metallic patterned layers and coherent excitations of spatially separated subwavelength resonators. Terahertz (THz) experiments show good agreement with numerical simulations.
关键词： Fabry-Pérot-like cavity,broadband,THz experiments,linear polarization converter,high efficiency,bi-layer metamaterial,coherent excitations,high transmittance
更新于2025-09-09 09:28:46
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[IEEE 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz 2018) - Nagoya (2018.9.9-2018.9.14)] 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - THz Near- Field Imaging and Spectroscopy with Nanoscale Resolution
摘要： Scattering-type near-field microscopy can overcome the limits in spatial resolution present in conventional THz imaging and spectroscopy techniques. This talk shows how THz near-field imaging and THz-TDS with a spatial resolution <20 nm can be realized with our neaSNOM microscope and some of the possible applications.
关键词： THz-TDS,nanoscale resolution,neaSNOM microscope,THz near-field imaging
更新于2025-09-04 15:30:14
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Generation of THz radiation by photoconductive antennas on based thin films InGaAs and InGaAs/InAlAs.
摘要： Epitaxial low-temperature grown (LT) semiconductor arsenides (Al, Ga, In)As are widely used as materials for photoconductive antennas (PCA) generators and detectors of pulsed radiation in the terahertz (THz) frequency range [1–3]. It is the combination of subpicosecond carrier lifetime, relatively high mobility and high resistivity that makes LT-materials suitable for PCA applications. Lately, InGaAs has been investigated as a potential candidate for THz-PCA photoconductive material due to room-temperature band gap of 0.74 eV, which allows for 1.56 μm optical excitation with Er3+ fiber laser femtosecond pulses [4–6]. The low substrate temperatures result in a non-stoichiometric growth with the incorporation of excess arsenic in the crystal structure. The most common non-stoichiometry-related point defects in LT-arsenides are arsenic antisites with concentrations in the range 1017–1019 cm-3 depending on the substrate temperature and arsenic overpressure [7–10]. Antisite-related defect band in the semiconductor energy bandgap play a significant role in carrier dynamics. Fast non-radiative recombination of photogenerated electrons and holes through antisite centers results in sub-picosecond carrier lifetimes in LT-materials at optimized growth and annealing conditions [11, 12]. It is generally agreed that main traps of photo-excited electrons are ionized antisite defects [13–15]. A possible approach to increase the resistivity of LT-InGaAs is to employ LT-InGaAs/InAlAs superlattices [6,13,16,17]. LT-InAlAs layers have a higher dark resistivity as compared to LT-InGaAs and exhibit deep trap states that are situated energetically below the antisite defect levels of adjacent InGaAs layers that results in a reduction of residual carrier concentration. The Fig.1 shows the amplitude of THz radiation in time domain. It is seen that the signal from an InGaAs /InAlAs-based structure is 5-6 times higher due to a higher bias voltage, which is possible (without sample breakdown) due to higher sample resistance and lower dark current. Fig.2 shows a comparison of the Fourier amplitude according to the materials of the antennas LT-InGaAs/InAlAs and LT-InGaAs. It is seen that the spectrum of the LT-InGaAs / InAlAs sample is slightly wider in the range from 0.1 THz to 0.6 THz than that of the LT-InGaAs sample. We explain this effect by the difference between the characteristic relaxation times of electrons in the transition from the conduction band to the antisites. We determined the characteristic times of electron relaxation by the 'pump-probe' spectroscopy method. Fig.3 shows the dependence of the normalized transmission in time domain for the samples of LT-InGaAs and LT-InGaAs / InAlAs.We used 2-exponentional model for description experimental curves. On figures τ1 is an electron capture time (capture by charge AsGa defects) [18,19], τ2 is a recombination time of captured electrons and holes [17]. Due to the experimental fact that the characteristic relaxation times for the LT-InGaAs / InAlAs sample are less than for the LT-InGaAs, we observed the difference in the spectra for these samples. Summing up, it was found that THz generation is about 5-6 times more efficient in the case of LT-InGaAs/InAlAs superlattice than LT-InGaAs generation. It is found that due to the shorter electron relaxation time in the superlattice, the spectrum of these samples is wider in the range of 0.1-0.6 THz.
关键词： photoconductive antennas,InGaAs,THz radiation,terahertz frequency range,InGaAs/InAlAs,LT-materials
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE International Conference on Computational Electromagnetics (ICCEM) - Chengdu (2018.3.26-2018.3.28)] 2018 IEEE International Conference on Computational Electromagnetics (ICCEM) - Roughness Impact on the RCS of Simple Canonical Objects in the Terahertz Regime
摘要： The higher the frequency is, the greater the influence of the precision and the realism of the CAD models on electromagnetic (EM) scattering characteristics are. In the terahertz (THz) regime, surfaces of most objects can’t be taken as smooth according to Rayleigh criterion. The interaction of EM waves and the surface presents a coherent part in the specular direction and a scattering part in the other directions. Unfortunately, the roughness of surface can’t be represented by the CAD geometry. Based on statistics theory, the rough surface height profile is fully determined by the height probability density function (pdf) and its autocorrelation functions. Without loss of generality, the height pdf of surface is assumed to be Gaussian. Under the assumption, the random Gaussian rough is correspondingly generated. The original CAD surface geometry and the random Gaussian rough surface are superposed as the input of EM computation. To demonstrate the roughness impact on RCS, EM scattering characteristics of simple canonical objects such as plate and dihedral in the THz regime are investigated. Taking into account the statistical surface roughness, the ray-based high-frequency EM method, shooting and bouncing rays (SBR), is utilized to compute the RCS of the objects above in the THz regime. Furthermore, the inverse synthetic aperture radar (ISAR) images are also carried out via filtered back projection (FBP) method. The EM scattering characteristics of the objects above in the THz regime are analyzed. Great differences of the objects EM scattering characteristics between the smooth and rough ones are observed and discussed.
关键词： roughness,shooting and bouncing rays,terahertz (THz),canonical objects
更新于2025-09-04 15:30:14
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Comparison of on-wafer TRL calibration to ISS SOLT calibration with open-short de-embedding up to 500 GHz
摘要： Sub-mm circuit design requires accurate on-wafer characterization of passive and active devices. In industry, characterization of these devices is often performed with off-wafer SOLT calibration. In this work, validity of this characterization procedure above 110 GHz is investigated by an exhaustive study of on-wafer and alumina off-wafer calibration using measurement and electromagnetic (EM) simulation up to 500 GHz. The EM simulation is performed at two different levels, first at the intrinsic level of the devices under test for reference and afterward up to the probe level to simulate different standards used in the off-wafer calibration or in the on-wafer calibration in presence of the probe. Further, EM simulation data is calibrated with the same procedures and tools that is used in the measurement; therefore, it includes the probe-to-substrate coupling. In addition, precise EM model of a commercial impedance standard substrate (ISS) is developed and used to perform the SOLT calibration. A good agreement is observed between measurement and EM modelling for the off-wafer calibration as well as for the on-wafer calibration. Results clearly highlights a limitation of alumina off-wafer methodology above 200 GHz for characterization of Silicon based technologies. Finally a discussion is given on the pros and cons of the off-wafer and on-wafer methodologies.
关键词： probe station,calibration,S-parameter measurement,TRL,THz,SiGe HBT,on-wafer,500 GHz,SOLT
更新于2025-09-04 15:30:14