[en] The spontaneous emission property of a five-level atom with a loop structure driven by three optical fields and a microwave field is intensively studied. Several quantum interference effects can be observed in the spontaneous emission spectra, such as spectral-line narrowing, spectral-line enhancement, spectral-line suppression, partial cancellation and fluorescence quenching. The number of emission peaks, the positions of dark lines can be controlled by varying the intensities of driving fields or the phase of the microwave field coupling the two lower levels in the atomic system. Furthermore, since no rigorous conditions are required, the expected phenomena may easily be achieved experimentally in atomic systems.

[en] We study the steady-state behaviour of spontaneous emission of a driven four-level atom embedded in photonic crystals. Considering different initial conditions, we discuss the influence of photonic band gap and detuning of external driving field on the atomic spontaneous emission spectrum. The photonic band gap and external driving field will impact strongly on the atomic spontaneous emission properties. Some interesting phenomena were found such as laser-induced dark line, laser-induced spectral-line narrowing and laser-induced pushing of a dressed state out of the band gap, which can be attributed to the quantum interference effect and control of the external driving field

[en] We study the influence of quantum interference on 2D sub-half-wavelength atom localization in a four-level atom driven by three external fields with a loop structure. When the dipoles of the two transitions from two upper levels to the lower level are parallel to each other, quantum interference between the two transitions arises. The analytical expression of conditional position probability (CPP) distribution is obtained using the iterative method. We discuss the influence of the detuning of the spontaneously emitted photon, the Rabi frequency of the microwave field and the dipole moment matrix element alignment p on the CPP. 2D sub-half-wavelength atom localization is obtained and the spatial resolution is improved significantly compared with cases with no quantum interference. (letter)

[en] We study the control of spontaneous emission in a three-level V-type atom that is coupled by a static magnetic field in photonic crystals. We find that by changing the position of the upper band edge and Larmor frequency of the magnetic field, control of the steady-state behavior of spontaneous emission can be achieved. As the transition frequencies move from outside the band gap to inside, the structure of the spectral line changes from a two-peak structure to a single-peak structure, and then to a non-Lorentzian shape. With the increase of the Larmor frequency of the magnetic field, when both transition frequencies are outside the photonic band gap, the partial spectral line disappears; however, when both frequencies are inside the band gap, the non-Lorentzian shape is replaced by a Lorentzian shape. These phenomena arise from the fact that the corresponding transition frequency is pushed into or out of the band gap. (paper)

[en] The martensitic transformation (MT), magnetic phases, and exchange bias (EB) effect in Mn₅₀Ni_{25 + x}In_25−x (x = 14.5∼18) Heusler alloys have been investigated. The MT and magnetic state can be tuned significantly by modifying the Ni/In ratio, while the Curie temperature (T_C) remains almost unchanged. With increase of the Ni/In ratio, the ferromagnetic components in the studied samples decrease continuously, while the antiferromagnetic components increase and it therefore enhances the exchange interaction as well. All of the samples exhibit negative horizontally shifted loops after field-cooled procedure. In addition, the samples with the compositional range of 15 ≤ x ≤ 16 also present the EB effect in zero field-cooled condition. To evaluate the causes of this scenario, EB field and coercive field as a function of temperature and cooling field have been investigated. The experimental results imply that the spin reconfiguration of superspin glass (SSG) clusters and the competition between antiferromagnetic and ferromagnetic interactions can account for the behavior of EB effect.

[en] In this work, hexagonal solid solutions of (Gd_0.95Eu_0.05)(OH)₃ with two distinctive morphologies of nanorods and nanotubes were successfully synthesized via hydrothermal treatment of mixed nitrate solutions in the presence of ammonium hydroxide. The hydroxide samples exhibited characteristic Eu³⁺ photoluminescence through the energy transfer from Gd³⁺ to Eu³⁺ and the self-excitation of Eu³⁺. The hydroxide precursors transformed into cubic (Gd_0.95Eu_0.05)₂O₃ at ∼500 deg. C via an intermediate monoclinic (Gd_0.95Eu_0.05)OOH phase, and the Eu³⁺ coordination accordingly experienced symmetry changes from D_3h to C_2v, and then to C₂/S₆. The cubic (Gd_0.95Eu_0.05)₂O₃ well retained the original morphologies of their polycrystalline precursors and exhibited a single-crystalline character at 1000 deg. C . Greatly enhanced photoluminescence (∼5000 times that of the hydroxides) was observed for the phase conversion.

[en] The spontaneous emission spectrum of a three-level Λ-type atom driven by a microwave field was studied. For the two transitions coupled to the same modified reservoir, we discussed the influence of photonic band gap and Rabi frequency of the microwave field on the emission spectrum. The emission spectrum is given for different locations of the upper band-edge frequency. With the transition frequencies moving from outside the band gap to inside, the number of peaks decreases in the emission spectrum and the multipeak structure of spectral line is finally replaced by a strong non-Lorentzian shape. With increase of the Rabi frequency of the microwave field, we find the spectral line changes from a multipeak structure to a two-peak structure, originating from the inhibition of spontaneous emission for the corresponding decay channel.

[en] This paper aims to develop an abnormal discharge detection device based on optical fiber signal transmission, and realize the reliable detection of abnormal discharge between fittings of high voltage electrical equipment. The detector and visible light detector developed in the arc light detection part can realize the efficient detection of ultraviolet light and visible light in the arc light. By optical fiber far - range signal transmission structure, this design developed multifunctional optical signal collector, which can be converted into analog electric signal, state quantity signal, digital quantity signal and other forms while collecting arc light efficiently. (paper)

[en] For a three-level Λ-type atom embedded in three-dimensional photonic crystals (PCs), the upper state population and spontaneous emission spectra are investigated with both transitions coupled to the same modified reservoir. By using an anisotropic dispersion model the analytic expressions of the upper state population and spontaneous emission spectra were obtained. The upper state population reaches a steady state value with a slight oscillation, and the spectra show a non-Lorentzian for both transition frequencies inside the band gap

[en] We report the phase evolution, microstructure, and critical current density (J_c) of the SiC doped MgB₂ superconductors. In our study, all samples were fabricated by hot pressing with a heating rate of 200 deg. C min^-1. The results show that the reaction of 2Mg+SiC = Mg₂Si+C can occur at about 500 deg. C, about 50 deg. C lower than the formation temperature of MgB₂. On the other hand, according to the experimental results and thermodynamic calculations, boron (B) does not react with SiC to form B₄C and Si, neither does MgB₂ react with SiC to form Mg₂Si and B₄C. The MgB₂ phase was formed via both a solid-solid reaction (during the heating process between about 500 and 650 deg. C) and a liquid-solid reaction (>650 deg. C) after the melting of Mg, and the two reactions resulted in differences in the grain size of the MgB₂. From scanning electron microscopy, the Mg₂Si particles are homogeneously distributed within the MgB₂ matrix, with particle sizes ranging from 35 to 230 nm. From the perspective of superconductivity, the C substitution results in strong electron scattering centers in the MgB₂ structure. It reduces the electron mean free path and thus may significantly enhance the magnetic J_c. The peak J_c of the 5 wt% SiC doped MgB₂ reaches above 10⁶ A cm^-2 at 5 K, and decreases slowly with increasing field, remaining high, above 10⁵ A cm^-2, at 7 T.