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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 Field Emission of Femto-Coulomb Electron Bunches
摘要： We demonstrate the sub-cycle optical field emission of electron wave packets with bunch charges up to 12 femtoCoulombs from a tungsten nanotip illuminated by intense THz pulses.
关键词： terahertz,field emission,tungsten nanotip,sub-cycle,electron bunches
更新于2025-09-10 09:29:36
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Growth of large-size high-quality ZnTe bulk crystals by traveling solvent melting zone method
摘要： ZnTe crystal is a promising electro-optical crystal materials applied for THz generation and detection. However, there is still a big challenge to obtain large sized high quality ZnTe crystals. In this work, large sized ZnTe bulk crystals with Φ30 mm × 150 mm were grown by the traveling solvent melting zone (TSMZ) method. With the characterization of the optical and electrical properties of as-grown ZnTe crystals, the band gap (2.22 eV), high IR transmittance (around 60%), high resistivity (3.5×103 ??cm), low density (1.3×105 cm-2) and small sizes (3μm - 5 μm) of Te inclusions in ZnTe crystals, low etch pit densities (1.5×105 cm-2), high peak intensity to FWHM ratio (2.5×104) of the LO peak in the Raman spectra were obtained. Furthermore, the THz transmission spectra was measured and the maximum transmittance is more than 40% at the range of 0.3 - 3THz. Based on these results, high quality and large aspect ratio ZnTe bulk crystals can be obtained by the TSMZ technique. Our work has greatly facilitated the application of ZnTe crystals in THz device.
关键词： terahertz,ZnTe,traveling solvent melting zone,electro-optical materials
更新于2025-09-10 09:29:36
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Simulating terahertz absorption of fluorinated phenylacetylene biphenyl liquid crystal molecules
摘要： Based on the density functional theory, ten kinds of fluoro-substituted liquid crystal derivative molecules, 4-butyl-4’-[(4-butylphenyl)acetylene]biphenyl, are simulated using Gaussian09 package with Opt+Freq optimization type and B3LYP/6-311g basis set. Comparing the substituted position and number of fluorine atoms, the absorption in terahertz region is discussed. Because measurement data of liquid crystal material absorption is lacking, we can only compare in the range of 0.3?3 THz. The results show that the calculation results have the same trend as the experimental measurement absorption curve of related literature. As a conclusion, our calculations can better reflect the absorption of molecular materials and provide effective suggestions for the design and synthesis of related molecules.
关键词： Gaussian simulation,absorption,fluorine liquid crystal,spectrum,terahertz
更新于2025-09-10 09:29:36
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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) - Intrinsic Losses in Dielectrics Investigated by Terahertz Spectroscopy
摘要： Low-loss dielectrics with various microstructure and, consequently, different extrinsic losses were investigated by using terahertz time-domain spectroscopy. The losses have been extrapolated and compared with those measured at microwave frequencies. The results showed that extrinsic factors have a considerably contribution in microwave domain. The intrinsic limit of dielectric loss of low absorption polycrystalline materials have been estimated by terahertz spectroscopy.
关键词： microwave frequencies,intrinsic losses,terahertz spectroscopy,extrinsic losses,dielectrics
更新于2025-09-10 09:29:36
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Electrical Control of Electromagnetically Induced Transparency by Terahertz Metamaterial Funneling
摘要： Electromagnetically induced transparency (EIT) analogs using metamaterials have diverse applications, including nonlinear optics, telecommunications, and biochemical sensors. These EIT analogs can be actively controlled by embedding semiconducting materials into metamaterial structures, but most active EIT metamaterials require complex optical setups and complicated fabrication processes. Graphene-based EIT metamaterials are some of the most promising active EIT systems because of their simple controllability by electrical bias, but related researches have so far been limited to theoretical or numerical studies. Here, experimentally verified graphene EIT metamaterials are provided by controlling the terahertz funneling of the unique metaatom structures. The proposed active EIT metamaterials are fabricated on flexible and ultrathin polyimide films to acquire the lowest substrate insertion losses and achieve a 1 ps group delay change at the transmission peak of the EIT analog. Moreover, because the proposed metamaterials exhibit resonance properties that vary depending on the polarization direction, the phase delay can be controlled up to 80° from the proposed metamaterials by rotating the incident polarization to the orthogonal direction. Overall, by controlling the group and phase delay of incident waves in a single metamaterial device simultaneously, a multifunctional active tuning system can be realized in the terahertz range.
关键词： terahertz,field enhancement,graphene,ion-gel,active metamaterials
更新于2025-09-10 09:29:36
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Absolute Terahertz Power Measurement of Tens of Nanowatts Using a Highly-Sensitive Calorimeter at Room Temperature
摘要： This study demonstrates a quantitative measurement of absolute terahertz power of tens of nanowatts at room temperature. A highly sensitive calorimetric measurement system is constructed using an extremely low noise amplifier and multilayer thermal insulation jackets. A vacuum insulator is used to mitigate thermal disturbance; therefore, very stable measurements are realized at room temperature. As a result, the absolute power of 26.7 nW is measured at 1 THz with the relative expanded uncertainty of 4.2% (k = 2).
关键词： Terahertz,traceability,calorimeter,uncertainty,absolute power
更新于2025-09-10 09:29:36
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Rectangular cavity-based perfect dual-band absorber with wide incidence angle in terahertz region
摘要： In this paper, a dual-band perfect metamaterial absorber(MA) based on rectangular cavity with wide incidence angle is proposed in the terahertz region. The unit of the absorber is composed of three different size rectangular cavities which are placed vertically on a metal plate. The numerical results show that the MA has two distinctive absorption bandwidths from 3.7586 to 4.0977 THz and 5.7635 to 6.0746 THz, respectively, with both absorption rates larger than 90%. Besides, the resonant frequency can be calculated based on rectangular cavity theory, which provides a design guideline for MA of such type. The theoretical predictions of the resonance frequencies have excellent agreements with the simulation ones. What’s more, the physical mechanism of the perfect absorption can be explained based on the distribution of E-field in the absorber and the standing wave theory. Our results provide a new way on realizing perfect absorption based on rectangular cavity.
关键词： terahertz,wide incidence angle,dual-band,metamaterial absorber,rectangular cavity
更新于2025-09-10 09:29:36
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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) - All-Electronic High-Resolution Terahertz Thickness Measurements
摘要： Broadband laser based terahertz systems become currently established for inline multilayer paint inspection in the automotive industry. This technology has also proven to be suitable for inspections of certain multilayer plastic structures with up to a few millimeters of thickness. We present a complementary technique for the measurement of dielectric multilayer structures with thicknesses of submillimeter to several centimeters, using frequency-modulated continuous-wave electronic transceivers. In order to resolve layers below the inherent resolution limit by the modulation bandwidth, we take advantage of model-based signal processing techniques.
关键词： signal processing,thickness measurements,frequency-modulated continuous-wave,terahertz,multilayer structures
更新于2025-09-10 09:29:36
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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 Microfluidic Metamaterial Biosensor for Tiny Volume Liquid Samples
摘要： We present a novel multi-microfluidic-channel metamaterial biosensor (MCMB) for highly sensitive terahertz (THz) sensing of tiny volume liquid samples. The multi-channels are set mainly in the strong electric field enhancement area of the metamaterial, which significantly decreases the liquid amount and enhances interaction between the sensing targets and the THz wave (thus increasing the sensitivity). The water sensing results demonstrate the effectiveness of this proposed design and the great potential in THz biosensing.
关键词： metamaterial,biosensor,liquid samples,terahertz,microfluidic
更新于2025-09-10 09:29:36
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On the Fractal Absorption Spectra of Polymers in the Low-Frequency Part of the Terahertz Range
摘要： The power dependence α(ν) ∝ νμ, where μ > 0 is the power exponent which is noninteger in the general case, is observed for amorphous polymers with a small absorption coe?cient α in the low-frequency part of the terahertz range, which approximately corresponds to the frequencies ν from 0.1 to 2–3 THz. This dependence is fractal, which is due to the fractal structure of the polymer macromolecules. In this work, we ?nd the power-law index at room temperature for the absorption coe?cient of some amorphous polymers. This index is determined on the basis of the dynamics of transmission of a broadband picosecond terahertz pulse through the polymer sample, i.e., using the method of the pulse terahertz spectroscopy in the time-domain representation.
关键词： terahertz range,fractal absorption spectra,polymers,fractal structure,power-law index
更新于2025-09-10 09:29:36