Analysis of Coupling between DR and Microstrip

The coupling between dielectric resonator (DR) and microstrip is theoretically analyzed in thispaper.The equivalent circuit and corresponding components' expression are achieved.Also,the formula of thecoupling ratio is deduced,which is the critical parameter to calculate the values of components.The analysis of thepaper can be used in modeling and strict design in DR applications such as dielectric resonator oscillators(DROs)and DR filters.At the end of the paper,an example of DRO design based on the analysis above is given.Thecoincidence between modulation and measure shows the significance of the paper.     

Coupling Effect Analysis of Multiwaveguides by FDTD Method

By use of finite-difference time-domain(FDTD)method,an eignmode analysis in a multiwaveguide structure is presented.Because of difference in propagation constants of different modes,coupling effect is discussed for three and five waveguide systems.The field distribution in multiwaveguides is given.     

Enhancement of Spin–Orbit Interaction by Bandgap Engineering in InAs-Based Heterostructures

We investigated Rashba spin–orbit interaction in various InAs-based heterostructures to evaluate the relative significance of the electric field in the quantum wells (QWs) and at the interfaces. Test structures were designed in such a way that the peak of the electron wave function was located on the abrupt band discontinuity at the front end of the main channel, whereas a control sample had no band discontinuity in the middle of the QW. The Rashba coefficient obtained for the test structures was almost double that of the control sample. Significant contribution of the electric field at the band discontinuity was verified by k · p calculation. Bandgap engineering was shown to be effective for obtaining an increased Rashba coefficient.     

Matrix Calculation of the Spectral Characteristics of AII–BVI Semiconductors Doped with Iron-Group Ions

A method for the matrix calculation of the spectral characteristics of AII–BVI semiconductors doped with iron-group ions is proposed, which takes into account all possible interactions in the ion and the effect of intramolecular surrounding fields of different symmetries. A technique for calculating the oscillator strength on the basis of eigenfunctions of the resulting states of 3d⁷, 3d⁸, and 3d⁶ electron configurations is developed. The spectral regularities of the Co²⁺, Ni²⁺, and Fe²⁺ energy structures for the ZnO, ZnS, ZnSe, ZnTe, CdO, CdS, CdSe, and CdTe materials are studied. All possible spectral bands in iron-group ions implanted in AII–BVI semiconductors in the range of 1.3–3 μm are established. The possibility of implementing the laser effect on these materials is estimated.     

Enhancement of Spin–Orbit Torque by Strain Engineering in SrRuO3 Films

Complex oxides with 4d/5d transition metal ions, e.g., SrRuO₃, usually possess strong spin–orbit coupling, which potentially leads to efficient charge-spin interconversion. As the electrical transport property of SrRuO₃ can be readily tuned via structure control, it serves as a platform for studying the manipulation of charge-spin interconversion. Here, a factor of twenty enhancement of spin–orbit torque (SOT) efficiency via strain engineering in a SrRuO₃/Ni₈₁Fe₁₉ bilayer is reported. The results show that an orthorhombic SrRuO₃ leads to a higher SOT efficiency than the tetragonal one. By changing the strain from compressive to tensile in the orthorhombic SrRuO₃, the SOT efficiency can be increased from an average value of 0.04 to 0.89, corresponding to a change of spin Hall conductivity from 27 to 441 × ħ/e (S cm⁻¹). The first-principles calculations show that the intrinsic Berry curvature can give rise to a large spin Hall conductivity (SHC) via the strain control, which is consistent with the experimental observations. The results provide a route to further enhance the SOT efficiency in complex oxide-based heterostructures, which will potentially promote the application of complex oxides in energy-efficient spintronic devices.     

NbIr2B2 and TaIr2B2 – New Low Symmetry Noncentrosymmetric Superconductors with Strong Spin–Orbit Coupling

Superconductivity was first observed more than a century ago, but the search for new superconducting materials remains a challenge. The Cooper pairs in superconductors are ideal embodiments of quantum entanglement. Thus, novel superconductors can be critical for both learning about electronic systems in condensed matter and for possible application in future quantum technologies. Here two previously unreported materials, NbIr₂B₂ and TaIr₂B₂, are presented with superconducting transitions at 7.2 and 5.2 K, respectively. They display a unique noncentrosymmetric crystal structure, and for both compounds the magnetic field that destroys the superconductivity at 0 K exceeds one of the fundamental characteristics of conventional superconductors (the “Pauli limit”), suggesting that the superconductivity may be unconventional. Supporting this experimentally based deduction, first-principle calculations show a spin-split Fermi surface due to the presence of strong spin–orbit coupling. These materials may thus provide an excellent platform for the study of unconventional superconductivity in intermetallic compounds.     

Analysis of Current–Voltage Characteristics in UV AlGaN Heterostructure FPAs

Journal of Communications Technology and Electronics - UV visible-blind and solar-blind 320 × 256 photodiode arrays based on AlxGa1 – xN heteroepitaxial structures (AlGaN HES) and...     

Untangling the Fundamental Electronic Origins of Non-Local Electron–Phonon Coupling in Organic Semiconductors

Organic semiconductors with distinct molecular properties and large carrier mobilities are constantly developed in attempt to produce highly-efficient electronic materials. Recently, designer molecules with unique structural modifications have been expressly developed to suppress molecular motions in the solid state that arise from low-energy phonon modes, which uniquely limit carrier mobilities through electron–phonon coupling. However, such low-frequency vibrational dynamics often involve complex molecular dynamics, making comprehension of the underlying electronic origins of electron–phonon coupling difficult. In this study, first a mode-resolved picture of electron–phonon coupling in a series of materials that are specifically designed to suppress detrimental vibrational effects, is generated. From this foundation, a method is developed based on the crystalline orbital Hamiltonian population (COHP) analyses to resolve the origins—down to the single atomic-orbital scale—of surprisingly large electron–phonon coupling constants of particular vibrations, explicitly detailing the manner in which the intermolecular wavefunction overlap is perturbed. Overall, this approach provides a comprehensive explanation into the unexpected effects of less-commonly studied molecular vibrations, revealing new aspects of molecular design that should be considered for creating improved organic semiconducting materials.     

Capacity Analysis of Adaptive Transmission with Space–Time Block Codes in Spatially Correlated MIMO Nakagami-m Fading Channels

In this paper we investigate the impacts of spatial fading correlation on channel capacity of orthogonal space–time block codes (STBCs) over multiple-input multiple-output Nakagami- \(m\) fading under different power and rate allocation policy. This paper presents the single-input single-output equivalency of STBC which is equivalent to scalar additive white Gaussian noise channel, with a channel gain proportional to the Frobenius norm of the matrix channel. We derive the characteristic function (c.f.) of the signal-to-noise ratio at the output of the STBC decoder, when spatial fading correlation is assumed. The c.f. turns out to be a linear combination of Laplace transforms weighted by the eigenvalues of the channel correlation matrix, where each element corresponds to an elementary Gamma probability density function. Based on this approach, and using the linearity of the Laplace transform, the capacity expressions are derived for STBC under different adaptive transmission policy. Numerical results illustrate the impact of fading correlation and fading severity on the channel capacity and outline the performance differences between the distinctive adaptation policies.     

Performance Analysis of Slotted Multichannel ALOHA Systems with Capture in Microcellular Environments

ＰｅｒｆｏｒｍａｎｃｅＡｎａｌｙｓｉｓｏｆＳｌｏｔｔｅｄＭｕｌｔｉｃｈａｎｎｅｌＡＬＯＨＡＳｙｓｔｅｍｓｗｉｔｈＣａｐｔｕｒｅｉｎＭｉｃｒｏｃｅｌｌｕｌａｒＥｎｖｉｒｏｎｍｅｎｔｓＸｉａｏｘｉｎＱｉｕ；ＶｉｃｔｏｒＯ．Ｋ．Ｌｉ（Ｕｎｉｖｅｒｓｉｔｙｏ...     

Quantum Oscillations of Thermoelectric Effects in a Pseudo-one-dimensional Electron Gas With a Spin–Orbit Interaction

We consider thermoelectric effects in a pseudo-one-dimensional electron gas (P1DEG) with a spin–orbit interaction (SOI). The SOI splits the dispersion relation of the P1DEG into subbands with an energy gap. We find quantum oscillations in transport coefficients, which coincide with the locations of the subband edges, as a function of the electrochemical potential.     

Technique for the Electrochemical Capacitance–Voltage Profiling of Heavily Doped Structures with a Sharp Doping Profile

Semiconductors - The specific features of applying electrochemical capacitance–voltage profiling to investigate heavily doped structures with a sharp doping profile are considered. Criteria...     

Optimization Design of Superluminescent Diodes with RWGStructure for High Efficiency Coupling with SMFs

为了提高脊波导结构的超辐射二极管（SLD）与单模光纤的耦合功率，研究了有源区与脊之间的残留层和上光限制层的厚度对SLD输出功率和近场光斑的影响. 考虑了注入载流子横向分布的不均匀，较准确地计算了模式增益. 结果表明，通过对残留层和上光限制层厚度的优化，可以有效提高SLD与单模光纤的耦合功率.     

Activation of Self-Trapped Emission in Stable Bismuth-Halide Perovskite by Suppressing Strong Exciton–Phonon Coupling

All-inorganic bismuth-halide perovskites are promising alternatives for lead halide perovskites due to their admirable chemical stability and optoelectronic properties; however, these materials deliver inferior photoluminescence (PL) properties, severely hindering their prospects in lighting applications. Here, a novel air-stable but non-emissive perovskite Rb₃BiCl₆ is synthesized, and the material is used as a prototype to uncover origin of the poor optical performance in bismuth-halide perovskite. It is found that the extremely strong exciton–phonon interactions with a large coupling constant up to 693 meV leads to the seriously nonradiative recombination, which, however, can be effectively suppressed to 347 meV by introducing Sb³⁺ ions. As a result, Sb³⁺-doped Rb₃BiCl₆ exhibits a stable yellow emission with unprecedented PL quantum yield up to 33.6% from self-trapped excitons. Systematic spectroscopic characterizations and theoretical calculations are carried out to unveil the intriguing photophysical mechanisms. This work reveals the effect of exciton–phonon interaction, that is often underemphasized, on a material's photophysical properties.     

Analysis of Outage Probability in Wavelength Diversity Based FSO Link Under Gamma–Gamma Fading with Varying Atmospheric Attenuation

Wireless Personal Communications - Free space optical (FSO) communication links offers an emerging alternative to RF communication links because of high speed, secure and cost-effective options to...     

Performance Analysis of a DS-CDMA Cellular System with Effects of Soft Handoff in Log-Normal Shadowing Channels

Next generation wireless communication is based on a global system of fixed and wireless mobile services thatare transportable across different network back-bones,network service providers and network geographical boundaries.This paper presents an approach to investigate the effects of soft handover and perfect power control on the forward link ina DS-CDMA cellular system.Especially,the relationships between the size ofhandover zone and the capacity gain are e-valuated under the log-normal shadow channel.Then the optimization of maximum forward capacity is very necessary tobe done with the maximum size of soft handover zone to the various system characteristics.     

Characteristics of High-power GaAs Laser Beams and Their Coupling with Fibers

The beams of 980nm high-power LDs are analyzed, and the reasons that aspect ratio of LD beams is high are explained. It is certified by the test that cylindrical lens can efficiently compress the perpendicular divergence angle of the beam. Some typical and popular lensed fibers were compared and analyzed according to coupling characteristics. The factors which affect the coupling efficiency and tolerance of the wedged-shaped GRIN tipped lensed fiber are pointed out, and some methods to reduce the coupling loss of the lensed fibers are proposed finally.     

Analysis of Phonon Modes and Electron–Phonon Interaction in Quantum-Cascade Laser Heterostructures

Semiconductors - The phonon modes of quantum-cascade heterostructures based on binary and ternary semiconductor compounds are simulated. The dependences of the frequencies of the structure...