Catálogo de publicaciones - revistas

<jats:p>We investigate nonlocal advantage of quantum coherence (NAQC) in a correlated dephasing channel modeled by the multimode bosonic reservoir. We obtain analytically the dephasing and memory factors of this channel for the reservoir having a Lorentzian spectral density, and analyze how they affect the NAQC defined by the <jats:italic>l</jats:italic> <jats:sub>1</jats:sub> norm and relative entropy. It is shown that the memory effects of this channel on NAQC are state-dependent, and they suppress noticeably the rapid decay of NAQC for the family of input Bell-like states with one excitation. For the given transmission time of each qubit, we also obtain the regions of the dephasing and memory factors during which there is NAQC in the output states.</jats:p>

<jats:p>Counter-rotating-wave terms (CRWTs) are traditionally viewed to be crucial in open small quantum systems with strong system–bath dissipation. Here by exemplifying in a nonequilibrium qubit–phonon hybrid model, we show that CRWTs can play the significant role in quantum heat transfer even with weak system–bath dissipation. By using extended coherent phonon states, we obtain the quantum master equation with heat exchange rates contributed by rotating-wave-terms (RWTs) and CRWTs, respectively. We find that including only RWTs, the steady state heat current and current fluctuations will be significantly suppressed at large temperature bias, whereas they are strongly enhanced by considering CRWTs in addition. Furthermore, for the phonon statistics, the average phonon number and two-phonon correlation are nearly insensitive to strong qubit–phonon hybridization with only RWTs, whereas they will be dramatically cooled down via the cooperative transitions based on CRWTs in addition. Therefore, CRWTs in quantum heat transfer system should be treated carefully.</jats:p>

<jats:p>We report on a research of the loading of ultracold sodium atoms in an optical dipole trap, generated by two beams from a high power fiber laser. The effects of optical trap light power on atomic number, temperature and phase space density are experimentally investigated. A simple theory is proposed and it is in good accordance with the experimental results of the loaded atomic numbers. In a general estimation, an optimal value for each beam with a power of 9 W from the fiber laser is achieved. Our results provide a further understanding of the loading process of optical dipole trap and laid the foundation for generation of a sodium Bose–Einstein condensation with an optical dipole trap.</jats:p>

<jats:p>We simulate the polarization manipulation of bright-dark vector bisolitons at 1-μm wavelength regime. Through changing the pulse parameters, different kinds of pulse shapes and optical spectra are generated in output orthogonal polarization directions. When the input vector bisoliton is polarization-locked with 1064 nm central wavelength, “1+1” fundamental dark-dark and “2+1” pseudo-high-order bright-dark group-velocity-locked vector solitons can be achieved through changing the projection angle. When the input vector bisoliton is group-velocity-locked with 1063 nm and 1065 nm central wavelengths, “2+1” and “2+2” pseudo-high-order bright-dark group-velocity-locked vector solitons, bright-dark group-velocity-locked vector solitons with chirp-like temporal oscillations are generated. Our simulation results can provide beneficial conduct for polarization manipulation of vector multi-solitons, and have promising applications in quantum information register, optical communications, nanophotonics, and all-optical switching.</jats:p>

<jats:p>We reported a chalcogenide glass-based rib waveguide fabricated using photolithography and dry etching method. A commercial software (COMSOL Multiphysics) was used to optimize the waveguide structure and the distribution of the fundamental modes in the waveguide based on the complete vector finite component. We further employed thermal annealing to optimize the surface and sidewalls of the rib waveguides. It was found that the optimal annealing temperature for GeAsSeS films is 220 °C, and the roughness of the films could be significantly reduced by annealing. The zero-dispersion wavelength (ZDW) could be shifted to a short wavelength around ∼ 2.1 μm via waveguide structural optimization, which promotes supercontinuum generation with a short wavelength pump laser source. The insertion loss of the waveguides with cross-sectional areas of 4.0 μm × 3.5 μm and 6.0 μm × 3.5 μm was measured using lens fiber and the cut-back method. The propagation loss of the 220 °C annealed waveguides could be as low as 1.9 dB/cm at 1550 nm.</jats:p>

<jats:p>A beam steering effect of high-power quantum cascade (QC) lasers emitting at ∼ 4.6 μm was investigated. The continuous wave (CW) output power of an uncoated, 6-mm-long, 7.5-μm-wide buried-heterostructure QC laser at 25 °C was as high as 854.2 mW. The maximum beam steering angle was offset by ± 14.2° from the facet normal (0°) in pulsed mode. The phenomenon was judged explicitly by combining the diffraction limit theory and Fourier transform of the spectra. It was also verified by finite element method software simulation and the calculation of two-dimensional (2D) effective-index model. The observed steering is consistent with a theory for coherence between the two lowest order lateral modes. Therefore, we have established an intrinsic linkage between the spectral instabilities and the beam steering by using the Fourier transform of the spectra, and further presented an extremely valid method to judge the beam steering. The content of this method includes both three equidistant peak positions in the Fourier transform of the spectra and the beam quality located between once the diffraction limit (DL) and twice the DL.</jats:p>

<jats:p>High quality Zn<jats:sub>0.5</jats:sub>Co<jats:sub> <jats:italic>x</jats:italic> </jats:sub>Fe<jats:sub>2.5 – <jats:italic>x</jats:italic> </jats:sub>O<jats:sub>4</jats:sub> (<jats:italic>x</jats:italic> = 0, 0.05, 0.1, 0.15) serial magnetic nanoparticles with single cubic structures were prepared by the modified thermal decomposition method, and Zn<jats:sub>0.5</jats:sub>Co<jats:sub> <jats:italic>x</jats:italic> </jats:sub>Fe<jats:sub>2.5 – <jats:italic>x</jats:italic> </jats:sub>O<jats:sub>4</jats:sub>/SiO<jats:sub>2</jats:sub> composite magnetic nanoparticles were prepared by surface modification of SiO<jats:sub>2</jats:sub>. The magnetic anisotropy of the sample increases with the increase of the doping amount of Co<jats:sup>2+</jats:sup>. When the doping amount is 0.1, the sample shows the transition from superparamagnetism to ferrimagnetism at room temperature. In the Zn<jats:sub>0.5</jats:sub>Co<jats:sub> <jats:italic>x</jats:italic> </jats:sub>Fe<jats:sub>2.5 – <jats:italic>x</jats:italic> </jats:sub>O<jats:sub>4</jats:sub>/SiO<jats:sub>2</jats:sub> serial samples, the maximum value of specific loss power (SLP) with 1974 W/g<jats:sub>metal</jats:sub> can also be found at doping amount of <jats:italic>x</jats:italic> = 0.1. The composite nanoparticles are expected to be an excellent candidate for clinical magnetic hyperthermia.</jats:p>

<jats:p>Vertical GaN Schottky barrier diodes with TiN anodes were fabricated to investigate the electrical performance. The turn-on voltage and specific on-resistance of diodes are deduced to be approximately 0.41 V and 0.98 mΩ⋅cm<jats:sup>2</jats:sup>, respectively. The current-voltage curves show rectifying characteristics under different temperatures from 25 °C to 200 °C, implying a good thermal stability of TiN/GaN contact. The low-frequency noise follows a 1/<jats:italic>f</jats:italic> behavior due to the multiple traps and/or barrier inhomogeneous at TiN/GaN interface. The trapping/de-trapping between traps and Fermi level causes the slight capacitance dispersion under reverse voltage.</jats:p>

<jats:p>The toxicity and degradation of hybrid lead-halide perovskites hinder their extensive applications. It is thus of great importance to explore non-toxic alternative materials with excellent stability and optoelectronic property. We investigate the atomic structures and optoelectronic properties of non-toxic organic tin bromide perovskites (OTBP) with one/zero-dimensional (1D/0D) structures by first-principles calculations. The calculated atomic structures show that the 1D/0D OTBPs are stable and the structure of inorganic octahedra in 0D is higher order than that in 1D. Moreover, the origination of exceptional purity emitting light in experiments is explained based on the calculated electronic structure.</jats:p>

<jats:p>Hard coatings have been widely applied to enhance tribological performance of mechanical components. However, it was predicted that thin hard coatings may have a weakening effect which could reduce the coating/substrate system’s resistance to plastic yielding compared with the uncoated substrate material. In this paper, analytical simulation is utilized to investigate the origin of weakening effect. The functions of material mechanical properties and coating thickness on the weakening effect are theoretically investigated. Partial-unloading spherical nanoindentation tests are performed on tungsten coated single crystalline silicon and copper to acquire the stress-strain curves and compared with the uncoated cases. The experimental results are in consistence with the analytical solutions, demonstrating the presence of weakening effect.</jats:p>