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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) - Determining DHO detection limits for a frequency domain THz spectrometer coupled to a light-weight multi-pass sample cell
摘要： A terahertz spectrometer connected to a custom fabricated, light-weight multi-meter multi-pass sample cell was employed to measure the 1.492 THz, 1.507 THz and 1.523 THz molecular transitions of DHO over various pressures. We will report on the detectable concentrations of the DHO achieved with the portable instrument.
关键词： portable instrument,DHO,terahertz spectroscopy,multi-pass sample cell
更新于2025-09-16 10:30:52
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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) - Terahertz Wave Generation Using Single or Few-cycle Laser Pulses in a Gaseous Medium
摘要： We perform theoretical calculations to demonstrate that single or few-cycle laser pulses (at the wavelength of 800 nm) can generate an intense terahertz emission by a directional current. Terahertz (THz) radiation exhibits a strong dependence on the carrier-envelope phase (CEP) of the driving laser pulse as the duration decreases. The strength of the THz radiation is pronounced at the CEP of 90 deg. The design of an experimental setup to demonstrate THz wave generation using single or few-cycle laser pulses in a gaseous medium is also demonstrated.
关键词： directional current,single or few-cycle laser pulses,Terahertz wave generation,carrier-envelope phase (CEP)
更新于2025-09-16 10:30:52
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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) - Terahertz Differential Absorption Spectroscopy Using Multi-Furcated Nd:YAG Microchip Laser for Gas Sensing
摘要： We demonstrate a frequency-domain differential absorption spectroscopy in the terahertz (THz) range for gas sensing applications. Our system is based on an injection-seeded THz-wave parametric generator driven by a multi-furcated Nd:YAG microchip laser. Within a single excitation cycle of the laser, the is-TPG generates up to three narrowband THz-wave pulses that are separated from each other in time by 78 μs and in frequency by 11 GHz, which is due to the spatial hole burning effect in the laser cavity. These pulses can be directly used to measure differential absorption signals, and first and second derivative spectra of target gas molecules without measuring reference spectra.
关键词： Nd:YAG microchip laser,gas sensing,differential absorption spectroscopy,THz-wave parametric generator,terahertz
更新于2025-09-16 10:30:52
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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) - Terahertz Emission from an Asymmetric Dual-Grating-Gate InGaAs High-Electron-Mobility Transistor Stimulated by Plasmonic Boom Instability
摘要： Asymmetric dual-grating-gate InGaAs high-electron-mobility transistors (ADGG-HEMTs) are studied as plasmonic terahertz (THz) emitters. We experimentally observed THz emission from a fabricated device at 110K. The spectra showed a broadband resonant emission under low d.c. channel currents reflecting radiation decay of thermally excited plasmons. With increasing the current and longitudinal electric field the emission was enhanced in a narrower spectral range suggesting promotion of plasmonic instability. Its threshold behavior suggests the occurrence of plasmonic-boom-type instability.
关键词： terahertz emission,plasmonic instability,asymmetric dual-grating-gate,high-electron-mobility transistors,InGaAs
更新于2025-09-16 10:30:52
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Formation of a Nanoscale Graphite Hydrosol under the Influence of Terahertz Laser Radiation
摘要： The present report describes a new phenomenon, namely the formation of a nanoscale hydrosol during short-term exposure of the surface of water by focused terahertz radiation of the Novosibirsk free-electron laser. The composition of the particles is completely determined by the material of the container used. Hydrosols are technologically convenient forms for scientific and industrial applications, which are characterized by uniform deposition and high catalytic activity used in medicine, optics, and as a suspension for sample preparation for chemical and elemental analysis. This article presents the results of our study of graphite particles formed in water, a suspension, which is in demand for industrial purposes. Commercially available high purity graphite (99.5%) of GE grade is used. The initial material and the resulting particles are studied using an atomic force and electron microscope with an elemental analyzer.
关键词： terahertz radiation,Novosibirsk FEL,nanoparticles,graphite,hydrosol
更新于2025-09-16 10:30:52
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Tunable localized surface plasmon graphene metasurface for multiband superabsorption and terahertz sensing
摘要： We propose a plasmon induced tunable metasurface for multiband superabsorption and terahertz sensing. It consists of a graphene sheet that facilitates perfect absorption where the graphene pattern at the top layer creates an enhanced evanescent wave that facilitates the metasurface to work as a sensor. The modelling and numerical analysis are carried out using Finite Element Method (FEM) based software, CST microwave studio where a genetic algorithm (GA) is used to optimize the geometric parameters, and metasurface tunability is achieved via an external gate voltage on the graphene. By exploiting graphene’s tunable properties we demonstrate a multiband superabsorption spectra having a maximum absorption of 99.7% in a frequency range of 0.1–2.0 THz that also maintain unique optical performance over a wide incidence angle. Further results show how the superabsorber can be used as a sensor, where the resonance frequency shifts with the refractive index of the surrounding environment.
关键词： Absorber,Graphene,Terahertz Sensor,Metasurface
更新于2025-09-16 10:30:52
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Generation of Terahertz Radiation in Gas Media with Variable Structure when Focusing Two-Color Femtosecond Laser Pulses
摘要： The possibility of modulating the power of terahertz radiation generated in the laser plasma produced when focusing two-color femtosecond laser pulses in air, when using a gas jet directed to the plasma formation region, is demonstrated.
关键词： terahertz radiation,laser plasma,femtosecond pulses
更新于2025-09-16 10:30:52
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Multi-Energy Valley Scattering Characteristics for a SI-GaAs-Based Terahertz Photoconductive Antenna in Linear Mode
摘要： In this paper, the relationship between the terahertz radiation and the spatial distribution of photogenerated carriers under different bias electric field is studied. Terahertz pulses and the photocurrent of SI-GaAs photoconductive antenna are measured by the terahertz time-domain spectroscopy system. The occupancy rate for photogenerated carriers for different energy valleys is obtained by comparing the photocurrent of terahertz field integrating with respect to time with the photocurrent measured by oscilloscope. Results indicate that 93.04% of all photogenerated carriers are located in the Γ valley when the bias electric field is 3.33 kV/cm, and 68.6% of all photogenerated carriers are transferred to the satellite valley when the bias electric field is 20.00 kV/cm. With the bias electric field increasing, the carrier occupancy rate for the satellite valley tends to saturate at 72.16%. In order to obtain the carrier occupancy rate for the satellite valley and saturate value at the high bias electric field, an ensemble Monte Carlo simulation based on the theory of photo-activated charge domain is developed.
关键词： photoconductive antenna,multi-energy valley scattering,semi-insulating Gallium arsenide (SI-GaAs),terahertz time-domain spectroscopy
更新于2025-09-16 10:30:52
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Investigation of Phonon Scattering on the Tunable Mechanisms of Terahertz Graphene Metamaterials
摘要： The in?uences of di?erent kinds of phonon scatterings (i.e., acoustic (AC) phonon, impurity, and longitudinal optical (LO) phonon scatterings) on the tunable propagation properties of graphene metamaterials structures have been investigated, also including the e?ects of graphene pattern structures, Fermi levels, and operation frequencies. The results manifested that, at room temperature, AC phonon scattering dominated, while with the increase in temperature, the LO phonon scattering increased signi?cantly and played a dominate role if temperature goes beyond 600 K. Due to the phonon scatterings, the resonant properties of the graphene metamaterial structure indicated an optimum value (about 0.5–0.8 eV) with the increase in Fermi level, which were di?erent from the existing results. The results are very helpful to understand the tunable mechanisms of graphene functional devices, sensors, modulators, and antennas.
关键词： terahertz,metamaterials,phonon scatterings,graphene
更新于2025-09-16 10:30:52
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Tunable high-quality Fano resonance in coupled terahertz whispering-gallery-mode resonators
摘要： Fano resonance is widely discussed in designing functional terahertz components, such as sensors, ?lters, modulators, and group delay modules. Usually, a high quality (Q) factor and ?exible tunability of Fano resonance are key requirements for these applications. Here, we present tunable terahertz Fano resonance with a Q factor of 2095 at 0.439 THz in coupled terahertz whispering-gallery-mode resonators (WGMRs). Coupling between a relatively low Q (578) quartz ring and a high Q (2095) silicon ring is employed to generate high Q Fano resonance. The resonant frequency of the Fano resonance can be actively manipulated by tuning the resonant frequency of the high Q WGMR, which is achieved through utilizing an electrical thermo-optic tuning method; meanwhile, the resonance intensity of the Fano reso- nance can be engineered by adjusting the coupling strength between two WGMRs. This coupled-WGMR scheme delivers tunable high Q Fano resonance and may contribute to the design of high-performance con?gurable terahertz devices.
关键词： tunability,high Q factor,whispering-gallery-mode resonators,Fano resonance,terahertz
更新于2025-09-16 10:30:52