Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Optical enhancement cavity (OEC) is a powerful tool for fundamental research and diagnostics. In this paper, the progress of a continuous-wave OEC to realize of megawatt cavity for a novel light source based on a steady-state microbunching (SSMB) mechanism, is reported. After efficiently suppressing all external noise and optimizing the alignment, mode-matching, and polarization matching, stable and long-term locking is achieved with the help of two feedback loops. The modal instability phenomenon caused by the surface thermoelastic deformation is observed. A pair of D-shape mirrors are utilized to remove the high-order modes. Finally, an intra-cavity average power of 30 kW is reached.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Low-noise terahertz (THz) radiation over 100 MV/cm generation by a linearly-polarized relativistic laser pulse interacting with a near-critical-density (NCD) plasma slab is studied by theory and particle-in-cell (PIC) simulations. A theoretical model is established to examine the dipole-like radiation emission. The THz radiation is attributed to the single-cycle, low-frequency surface current which is longitudinally constrained by the quasi-equilibrium established by the laser ponderomotive force and the ponderomotively-induced electrostatic force. Through theoretical analysis, the spatiotemporal characteristics, polarization property of the THz radiation， and the relation between the radiation strength with the initial parameters of driving laser and plasma are obtained, which are in good consistence with the PIC simulation results. Furthermore, it is found by PIC simulations that the generation of thermal electrons can be suppressed within the appropriate parameter regime, resulting in a clear THz radiation waveform. The appropriate parameter region is given for generating a low-noise intense THz radiation with peak strength reaching 100 MV/cm, which could find potential applications in nonlinear THz physics.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Different from the Hermitian case, non-Hermitian (NH) systems have novel properties and strongly relate to open and dissipative quantum systems. In this work, we investigate how to simulate $\tau$-anti-pseudo-Hermitian systems in a Hermitian quantum device using linear combinations of unitaries and duality quantum algorithm. Specifying the $\tau$ to operators $T$ and $PT$, we construct the two NH two-level systems, design quantum circuits including three qubits, and decide the quantum gates explicitly in detail. We also calculate the success probabilities of the simulation. Experimental implementation can be expected in small quantum simulator.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report comprehensive investigations on the structure of high-quality (111)-oriented SrRuO<jats:sub>3</jats:sub>films on SrTiO<jats:sub>3</jats:sub> substrates to elucidate the effect of (111) heteroepitaxial strain. It is found that SrRuO<jats:sub>3</jats:sub> film of ~40 nm is compressively strained in plane on the substrate with full coherency. Nevertheless, the out-of-plane spacing is almost the same as its bulk, which is at odds with the conventional paradigm. By probing a series of half-order Bragg reflections using synchrotron-based x-ray diffraction combined with the analyses of the scanning transmission electron microscopy images, we discovered that the heteroepitaxial strain is accommodated via the significant suppression of the degree of <jats:italic>c</jats:italic> <jats:sup>+</jats:sup> octahedral tilting, and the formation of three equivalent domain structures on (111) SrTiO<jats:sub>3</jats:sub> substrate. This anomalous effect shed light on the understanding of unconventional paradigm of film-substrate coupling for the (111) heteroepitaxial strain.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Antimony selenide (Sb<jats:sub>2</jats:sub>Se<jats:sub>3</jats:sub>) films are widely used in phase change memory and solar cells due to their stable switching effect and excellent photovoltaic properties. These properties of the films are affected by the film thickness. A method combining the advantages of Levenberg-Marquardt method and Spectral Fitting Method (LM-SFM) is presented to study the dependence of refractive index (RI), absorption coefficient, optical band gap, Wemple-DiDomenico parameters, dielectric constant and optical electronegativity of Sb<jats:sub>2</jats:sub>Se<jats:sub>3</jats:sub> films on their thickness. The results show that the RI and absorption coefficient of Sb<jats:sub>2</jats:sub>Se<jats:sub>3</jats:sub> films increase with the increase of film thickness, while the optical band gap decreases with the increase of film thickness. Finally, the reasons why the optical and electrical properties of the film change with its thickness is explained by XRD, EDS, Mott-Davis state density model and Raman microstructure analysis.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The research progresses on the investigations of atomic structure and collision dynamics with highly charged ions based on the heavy ion storage rings and electron ion beam traps in recent 20 years are reviewed. The structure part covers test of quantum electrodynamics and electron correlation in strong Coulomb field studied through dielectronic recombination spectroscopy and VUV/x-ray spectroscopy. The collision dynamics part includes charge exchange dynamics in ion-atom collisions mainly in Bohr velocity region, ion induced fragmentation mechanisms of molecules, hydrogen-bound and van de Waals bound clusters, interference and phase information observed in ion-atom/molecule collisions. With this achievements, two aspects of theoretical studies related to low energy and relativistic energy collisions are presented. The applications of data relevant to key atomic processes like dielectronic recombination and charge exchanges involving highly charged ions are discussed. At end of this review, some future prospects of research related to highly charged ions are proposed.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A novel high performance carrier stored trench bipolar transistor (CSTBT) with dual shielding structure (DSS-CSTBT) is proposed in this paper. The proposed DSS-CSTBT features a double trench structure with different trench profiles in the surface, in which a shallow gate trench is shielded by a deep emitter trench and a thick oxide layer under it. Compared with the conventional CSTBT (Con-CSTBT), the proposed DSS-CSTBT not only alleviates the negative impact of the shallow gate trench and highly doped CS layer on the breakdown voltage (<jats:italic>BV</jats:italic>) but also well reduces the gate-collector capacitance (<jats:italic>C</jats:italic> <jats:sub>GC</jats:sub>), gate charge (<jats:italic>Q</jats:italic> <jats:sub>G</jats:sub>) and turn off loss (<jats:italic>E</jats:italic> <jats:sub>OFF</jats:sub>) of the device. Furthermore, lower turn on loss (<jats:italic>E</jats:italic> <jats:sub>ON</jats:sub>) and gate drive loss (<jats:italic>E</jats:italic> <jats:sub>DR</jats:sub>) are also obtained. Simulation results show that with the same CS layer doping concentration (<jats:italic>N</jats:italic> <jats:sub>CS</jats:sub>) of 1.5×10<jats:sup>16</jats:sup> cm<jats:sup>-3</jats:sup>, the <jats:italic>BV</jats:italic> increases from 1312 V of the Con-CSTBT to 1423 V of the proposed DSS-CSTBT with oxide layer thickness under gate (<jats:italic>T</jats:italic> <jats:sub>og2</jats:sub>) of 1μm. Moreover, compared with the Con-CSTBT, the <jats:italic>C</jats:italic> <jats:sub>GC</jats:sub> at <jats:italic>V</jats:italic> <jats:sub>CE</jats:sub> of 25 V and miller plateau charge (<jats:italic>Q</jats:italic> <jats:sub>GC</jats:sub>) for the proposed DSS-CSTBT with <jats:italic>T</jats:italic> <jats:sub>og2</jats:sub> of 1μm are reduced by 79.4% and 74.3%, respectively. With the <jats:italic>V</jats:italic> <jats:sub>GE</jats:sub> increases from 0 V to 15 V, the total <jats:italic>Q</jats:italic> <jats:sub>G</jats:sub> for the proposed DSS-CSTBT with <jats:italic>T</jats:italic> <jats:sub>og2</jats:sub> of 1μm is reduced by 49.5%. As a result, at the same on-state voltage drop (<jats:italic>V</jats:italic> <jats:sub>CEON</jats:sub>) of 1.55 V, the <jats:italic>E</jats:italic> <jats:sub>ON</jats:sub> and <jats:italic>E</jats:italic> <jats:sub>OFF</jats:sub> are reduced from 20.3 mJ/cm<jats:sup>2</jats:sup> and 19.3 mJ/cm<jats:sup>2</jats:sup> for the Con-CSTBT to 8.2 mJ/cm<jats:sup>2</jats:sup> and 9.7 mJ/cm<jats:sup>2</jats:sup> for the proposed DSS-CSTBT with <jats:italic>T</jats:italic> <jats:sub>og2</jats:sub> of 1μm, respectively. Thus, the proposed DSS-CSTBT not only significantly improves the trade-off relationship between the <jats:italic>V</jats:italic> <jats:sub>CEON</jats:sub> and <jats:italic>E</jats:italic> <jats:sub>OFF</jats:sub> but also greatly reduces the <jats:italic>E</jats:italic> <jats:sub>ON</jats:sub>.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Controlling the spin transport at the single-molecule level, especially without the use of ferromagnetic contacts, becomes a focus of research in spintronics. Inspired by the progress on atomic-level molecular synthesis, through first-principles calculations, we investigate the spin-dependent electronic transport of graphene nanoflakes with side-bonded functional groups, contacted by atomic carbon chain electrodes. It is found that, by rotating the functional group, the spin polarization of the transmission at the Fermi level could be switched between completely polarized and unpolarized states. Moreover, the transition between spin-up and spin-down polarized states can also be achieved, operating as a dual-spin filter. Further analysis shows that, it is the spin-dependent shift of density of states, caused by the rotation, that triggers the shift of transmission peaks, and then results in the variation of spin polarization. Such a feature is found to be robust to the length of the nanoflake and the electrode material, showing great application potential. Those findings may throw light on the development of spintronic devices.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A finite volume charge method has been proposed to simulate PIN diodes and IGBT devices using SPICE simulators by extending the lumped-charge method. The new method assumes the local quasi-neutrality in the un-depleted N- base region and uses the total collector current, the nodal hole density and voltage as the basic quantities. In SPICE implementation, it makes the clear and accurate definitions of three kinds of nodes: the carrier density nodes, the voltage nodes, and the current generator nodes in the un-depleted N- base region. It uses the central finite difference to approximate electron and hole current generators, and sets up the current continuity equation in a control volume for every carrier density node in the un-depleted N<jats:sup>-</jats:sup> base region. It is easy to increase the number of nodes to describe the fast spatially varying carrier density in transient processes. We use this method to simulate IGBT devices in SPICE simulators and get a good agreement with TCAD simulations.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The calcium fluoride (CaF<jats:sub>2</jats:sub>) whispering gallery mode crystalline resonator is an excellent platform for nonlinear optical applications because of the decreasing in threshold caused by ultrahigh quality (<jats:italic>Q</jats:italic>) factor. In this paper, we achieve the observation of Raman lasing, first-order Raman comb and second-order Raman lasing in a CaF<jats:sub>2</jats:sub> disk resonator with a diameter of 4.96 mm and an ultrahigh-<jats:italic>Q</jats:italic> of 8.43×10<jats:sup>8</jats:sup> at 1550 nm wavelength. We also observe thermal effects in CaF<jats:sub>2</jats:sub> disk resonator, and the threshold of thermo-optical oscillation is approximately coincident with Raman lasing, since the intracavity power increases rapidly when the power reaches the threshold, and higher input pump power results in longer thermal drift and higher Raman emission power. With a further increase in pump power, the optical frequency combs range is from 1520 nm to 1650 nm, with a wavelength interval of 4×<jats:italic>FSR</jats:italic>. It is a promising candidate for the optical communication, biological environment monitoring, spectral analysis, and microwave signal sources.</jats:p>