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oe1(光电查) - 科学论文

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出版时间
  • 2019
  • 2018
研究主题
  • microwave photonics
  • interdigital resonator
  • microwave gas sensor
  • PSE-coated
  • microwave photonic mixer
  • analog optical signal processing
  • phase shift
  • photonic array antenna
  • gain
  • integrate
应用领域
  • Optoelectronic Information Science and Engineering
机构单位
  • Inner Mongolia University
  • Jinan University
  • King Mongkut’s University of Technology North Bangkok
  • Beijing University of Posts and Telecommunications
  • Wroclaw University of Technology
  • Rajamangala University of Technology Suvarnabhumi
  • Southern University of Science and Technology
  • Charles Darwin University
  • University of Ottawa
  • University of Kent
508 条数据
?? 中文（中国） ▾

  • Perovskite Materials - Synthesis, Characterisation, Properties, and Applications || Microwave Dielectrics with Perovskite-Type Structure

    摘要： Most electroceramics are ferroelectrics, but microwave dielectrics are mostly paraelectrics with a center of symmetry i. Microwave dielectrics should possess a perfect crystal structure with neither defects nor internal strain in order to be microwave friendly. They have been used in resonators and filters in mobile telecommunications devices. Perovskite and related compounds are also mostly ferroelectrics, but paraelectrics with a perovskite structure also exist, and are used in microwave dielectrics. Owing to the flexibility of the perovskite structure, many kinds of microwave dielectrics with a perovskite structure have been designed for microwave dielectrics. In this chapter, simple and complex perovskite, and perovskite related materials such as pseudo-tungsten-bronze solid solutions and homologous compounds are introduced for microwave dielectrics. The microwave dielectric properties are revealed through the crystalline structure of the material. Therefore, the relationship between the crystalline structure and properties of the material is presented, and is expected to be of use in the design of novel dielectrics. As many superior materials for microwave dielectrics have been developed and are expected to be used in new applications such as wireless sensors and wireless power transfer by resonant coupling, wave absorption by interference and transparent ceramics with no birefringence, these new applications are also discussed.

    关键词： Tungsten-bronze compounds,Ordering,Homologous series,Microwave dielectrics,Complex Perovskite

    更新于2025-09-23 15:21:01

  • Coupling Rydberg Atoms to Microwave Fields in a Superconducting Coplanar Waveguide Resonator

    摘要： Rydberg helium atoms traveling in pulsed supersonic beams have been coupled to microwave fields in a superconducting coplanar waveguide (CPW) resonator. The atoms were initially prepared in the 1s55s 3S1 Rydberg level by two-color two-photon laser excitation from the metastable 1s2s 3S1 level. Two-photon microwave transitions between the 1s55s 3S1 and 1s56s 3S1 levels were then driven by the 19.556 GHz third-harmonic microwave field in a quarter-wave CPW resonator. This superconducting microwave resonator was fabricated from niobium nitride on a silicon substrate and operated at temperatures between 3.65 and 4.30 K. The populations of the Rydberg levels in the experiments were determined by state-selective pulsed electric field ionization. The coherence of the atom-resonator coupling was studied by time-domain measurements of Rabi oscillations.

    关键词： quantum electrodynamics,Rydberg atoms,microwave fields,superconducting coplanar waveguide resonator

    更新于2025-09-23 15:21:01

  • Structure stability, bond characteristics and microwave dielectric properties of co-substituted NdNbO4 ceramics

    摘要： Structure-property relationship of co-substituted (Mg2+1/4Mo6+3/4)5+, (Al3+1/3Mo6+2/3)5+, (Si4+1/2Mo6+1/2)5+, (Zr4+1/2Mo6+1/2)5+ for Nb5+ in NdNbO4 ceramics was investigated systematically. The remarkable differences in dielectric properties of each composition originated from their bond characteristics and structure stability. The elongated/compressed bonds have an effect on the cell volume and polarization. And the average bond covalency of Nb-O bond was responsible for the development of permittivity. Q×f values and the total lattice energy went up to maximum when (Si0.5Mo0.5) occupied Nb-site. Variations of lattice energy together with Nb-O bond energy suggest that a more stable structure was obtained through co-substitution. The optimal microwave dielectric properties is: εr=18.97, Q×f=49466GHz, τf=7.34 ppm/℃ for NdNb0.97(Si0.5Mo0.5)0.03O4, sintered at 1250℃.

    关键词： bond characteristics,Rietveld refinement,NdNbO4,microwave dielectric properties

    更新于2025-09-23 15:21:01

  • X-ray scintillator Gd2O2S:Tb3+ materials obtained by a rapid and cost-effective microwave-assisted solid-state synthesis

    摘要： In this work, the microwave-assisted solid-state (MASS) synthesis is reported as a rapid, cost-effective and environmental-friendly way to prepare Gd2O2S:Tb3+ X-ray scintillation standards. The preparation procedure employs active charcoal as the microwave susceptor, using a domestic microwave oven without a setup for special gases. The MASS method drastically reduced the synthesis time and energy consumption (up to 97% in nominal power) over previous reports using conventional solid-state methods. A single-step synthesis of 10 min is enough to yield highly crystalline powders starting from Gd2O3 and Tb4O7 precursors and elemental sulfur. In order to obtain 100% pure materials with superior scintillation efficiency, two microwave treatments of 25 min each are required. Due to the reducing CO atmosphere generated in situ by the active charcoal during the microwave synthesis, no Tb4+ impurity was found according to Synchrotron Radiation X-ray Absorption (SR-XAS) experiments. Spectroscopic studies were carried out using SR Vacuum-Ultraviolet (VUV) photoluminescence and SR X-ray Excited Optical Luminescence (XEOL). The material prepared by two-step synthesis exhibited a better scintillation performance owing to higher crystal purity and emission intensity, presenting versatility for technological applications such as X-ray imaging and scintillation bio-probing.

    关键词： Synchrotron Radiation,Gd2O2S:Tb3+,Microwave-assisted solid-state synthesis,X-ray scintillation

    更新于2025-09-23 15:21:01

  • Efficiency of Charge-Transfer Doping in Organic Semiconductors Probed with Quantitative Microwave and Direct-Current Conductance

    摘要： Although molecular charge-transfer doping is widely used to manipulate carrier density in organic semiconductors, only a small fraction of charge carriers typically escape the Coulomb potential of dopant counterions to contribute to electrical conductivity. Here, we utilize microwave and direct-current (DC) measurements of electrical conductivity to demonstrate that a high percentage of charge carriers in redox-doped semiconducting single-walled carbon nanotube (s-SWCNT) networks is delocalized as a free carrier density in the π-electron system (estimated as >46% at high doping densities). The microwave and four-point probe conductivities of hole-doped s-SWCNT films quantitatively match over almost 4 orders of magnitude in conductance, indicating that both measurements are dominated by the same population of delocalized carriers. We address the relevance of this surprising one-to-one correspondence by discussing the degree to which local environmental parameters (e.g., tube?tube junctions, the relative Coulombic stabilization, and local bonding environment) may impact magnitudes of each transport measurement.

    关键词： microwave conductivity,organic semiconductors,single-walled carbon nanotube,charge-transfer doping,DC conductivity

    更新于2025-09-23 15:21:01

  • Effect of illumination on quantum lifetime in GaAs quantum wells

    摘要： Low-temperature illumination of a two-dimensional electron gas in GaAs quantum wells is known to greatly improve the quality of high-field magnetotransport. The improvement is known to occur even when the carrier density and mobility remain unchanged, but what exactly causes it remains unclear. Here, we investigate the effect of illumination on microwave photoresistance in low magnetic fields. We find that the amplitude of microwave-induced resistance oscillations grows dramatically after illumination. Dingle analysis reveals that this growth reflects a substantial increase in the single-particle (quantum) lifetime, which likely originates from the light-induced redistribution of charge enhancing the screening capability of the doping layers.

    关键词： quantum lifetime,microwave photoresistance,GaAs quantum wells,illumination effect,two-dimensional electron gas

    更新于2025-09-23 15:21:01

  • [IEEE 2018 IEEE International Symposium on the Physical and Failure Analysis of Integrated Circuits (IPFA) - Singapore (2018.7.16-2018.7.19)] 2018 IEEE International Symposium on the Physical and Failure Analysis of Integrated Circuits (IPFA) - Nano C-V imaging of Semiconductor Devices with Scanning Microwave Impedance Microscopy

    摘要： Two doped semiconductor samples are measured using probe-based Scanning Microwave Impedance Microscopy (sMIM). One is a plan-view polished CMOS image sensor and the other is a cross-section polished power device. Both samples are imaged with sMIM using two different approaches: the first using a dual pass method with dC/dV images acquired simultaneously with sMIM during the first pass in contact mode, and the second pass at a fixed offset from the surface. The second method uses a non-resonant mode where C-V are acquired at specific lateral locations. The C-V curves are used to determine polarity compared to dC/dV and also to distinguish p-n junctions, characterize doping concentration, and build images at constant DC values to discern subtle changes not evident in traditional SCM imaging.

    关键词： Nano-C-V,SCM,Scanning Probe Microscopy,doping characterization,Scanning Microwave Impedance Microscopy,Scanning Capacitance Microscopy,sMIM

    更新于2025-09-23 15:21:01

  • [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) - Advance on Single Pressure Refractive Index Gas Thermometry

    摘要： A novel single pressure refractive index gas thermometry(SPRIGT) of thermodynamic temperature of helium gas filled in quasi-spherical microwave cavity resonator(QMCR) by combination of microwave measurements, temperature and pressure control. A long-term temperature stability better than 0.2mK is demanded for the QMCR from 5K to 24.5561 K. The uncertainty below 4ppm for pressure needs to precisely control the oscillation of temperature along the gas line. Microwave resonance frequency measurement in QMCR should be better than 2ppb. To meet these requirements, SPRIGT has been built in China and the first run experimental data was analysis in this paper.

    关键词： Pressure control,Temperature control,SPRIGT,Thermodynamic temperature,Microwave measurement,QMCR,Primary thermometry

    更新于2025-09-23 15:21:01

  • [IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - High Resolution Soil Moisture Product Based on Smap Active-Passive Approach Using Copernicus Sentinel 1 Data

    摘要： SMAP project released a new enhanced high-resolution (3km) soil moisture active-passive product. This product is obtained by combining the SMAP radiometer data and the Sentinel-1A and -1B Synthetic Aperture Radar (SAR) data. The approach used for this product draws heavily from the heritage SMAP active-passive algorithm. Modifications in the SMAP active-passive algorithm are done to accommodate the Copernicus Program’s Sentinel-1A and -1B multi-angular C-band SAR data. Assessment of the SMAP and Sentinel active-passive algorithm has been conducted and results show feasibility of estimating surface soil moisture at high-resolution in regions with low vegetation density (~< 3 kg m-2). The beta version of this product is released to public on Nov 1st, 2017. This high resolution (3 km) soil moisture product is useful for agriculture, flood mapping, watershed/rangeland management, and ecological/hydrological applications.

    关键词： active-passive algorithm,SMAP,Sentinel-1A and -1B,soil moisture,microwave remote sensing

    更新于2025-09-23 15:21:01

  • Monitoring of Microwave-Assisted Acid-Catalyzed Transesterification for Biodiesel Production Using FT-NIR Spectroscopy with Continuous-Flow Cell

    摘要： The homogeneous microwave-assisted sulfuric acid-catalyzed transesterification of soybean oil, waste Brazil nut oil, sunflower oil and chicken fat for ethylic and methylic biodiesel production is described herein. The experiments were carried out in pilot-scale multimode reactors. The effects of the alcohol to oil molar ratio, catalyst concentration and irradiation time on the conversion to biodiesel were investigated. The transesterification reactions were performed at relatively small alcohol to oil molar ratios (9:1, 8:1 and 6:1) affording near 100% of conversion in reaction times of 60 to 120 min. Partial least squares (PLS) regression analysis using FT-NIR spectroscopy was performed to monitor the progress of the acid-catalyzed methanolysis of soybean oil. The NIR spectra were collected during the transesterification reaction with a spectrophotometric continuous-flow cell. 1H NMR spectroscopy was employed to determine the conversion percentage and used as a reference to build the PLS calibration model employing NIR spectroscopy data.

    关键词： vegetable oils,sulfuric acid,FT-NIR spectroscopy,Animal fat,homogeneous acid catalysis,microwave-induced transesterification

    更新于2025-09-23 15:21:01