Catálogo de publicaciones - revistas

<jats:p>Molecular dynamics simulation of a sympathetically-cooled <jats:sup>113</jats:sup>Cd<jats:sup>+</jats:sup> ion crystal system is achieved. Moreover, the relationship between ions’ axial temperature and different electric parameters, including radio frequency voltage and end-cap voltage is depicted. Under stable trapping condition, optimum radio frequency voltage, corresponding to minimum temperature and the highest cooling efficiency, is obtained. The temperature is positively correlated with end-cap voltage. The relationship is also confirmed by a sympathetically-cooled <jats:sup>113</jats:sup>Cd<jats:sup>+</jats:sup> microwave clock. The pseudo-potential model is used to illustrate the relationship and influence mechanism. A reasonable index, indicating ions’ temperature, is proposed to quickly estimate the relative ions’ temperature. The investigation is helpful for ion crystal investigation, such as spatial configuration manipulation, sympathetic cooling efficiency enhancement, and temporal evolution.</jats:p>

<jats:p>A novel organized multipulse pattern and its birth dynamics under strong optomechanical effect in microfiber-assisted ultrafast fiber laser are investigated in this work. The background pulses are observed to obviously exhibit selectively amplifying self-organized process of evolving into quasi-stable equidistant clusters. The radio frequency spectrum of the multipulse pattern displays a harmonic mode-locking-like behavior with a repetition rate of 2.0138 GHz, corresponding to the frequency of torsional-radial (TR<jats:sub>2m</jats:sub>) acoustic mode in microfiber. The results show the evidence of optomechanical effect in dominating the birth dynamics and pattern of multipulse.</jats:p>

<jats:p>We develop a hybrid scheme of cross phase modulation based on electromagnetically induced transparency (EIT) and active Raman gain (ARG) in a multi-level atomic medium. The cross phase modulation, with low loss and without noise, is demonstrated in a room-temperature <jats:sup>85</jats:sup>Rb vapor. We show that a <jats:italic>π</jats:italic> radian nonlinear Kerr phase shift of the signal light relative to a reference light is observed when the signal light is modulated by the phase control field with the low light intensity. We also show that the linear and the third-order absorption can be eliminated via the Raman gain, and the phase noise of the signal light can be ignored when the phase control light is applied in this hybrid scheme.</jats:p>

<jats:p>High-order harmonics and attosecond pulse generation with coherent wake emission are theoretically investigated for the effect of pulse duration and carrier envelope phase (CEP) of few-cycle laser pulse. We find that short pulse duration will cause the negative chirp for the high harmonics. When the laser pulse is shortened to a few cycles, the influence of the laser CEP on the chirp of the harmonics will also become more prominent.</jats:p>

<jats:p>A biological sensing structure with a high-order mode (<jats:inline-formula> <jats:tex-math><?CDATA ${{\rm{E}}}_{21}^{y}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi mathvariant="normal">E</mml:mi> <mml:mrow> <mml:mn>21</mml:mn> </mml:mrow> <mml:mi>y</mml:mi> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_30_11_114208_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>) is designed, which is composed of a suspended racetrack micro-resonator (SRTMR) and a microfluidic channel. The mode characteristics, coupling properties, and sensing performances are simulated by using the finite element method (FEM). To analyze the mode confinement property, the confinement factors in the core and cladding of the suspended waveguide for the <jats:inline-formula> <jats:tex-math><?CDATA ${{\rm{E}}}_{11}^{x}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi mathvariant="normal">E</mml:mi> <mml:mrow> <mml:mn>11</mml:mn> </mml:mrow> <mml:mi>x</mml:mi> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_30_11_114208_ieqn2.gif" xlink:type="simple" /> </jats:inline-formula>, <jats:inline-formula> <jats:tex-math><?CDATA ${{\rm{E}}}_{11}^{y}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi mathvariant="normal">E</mml:mi> <mml:mrow> <mml:mn>11</mml:mn> </mml:mrow> <mml:mi>y</mml:mi> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_30_11_114208_ieqn3.gif" xlink:type="simple" /> </jats:inline-formula>, and <jats:inline-formula> <jats:tex-math><?CDATA ${{\rm{E}}}_{21}^{y}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi mathvariant="normal">E</mml:mi> <mml:mrow> <mml:mn>21</mml:mn> </mml:mrow> <mml:mi>y</mml:mi> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_30_11_114208_ieqn4.gif" xlink:type="simple" /> </jats:inline-formula> are calculated. The simulation results show that the refractive index (RI) sensitivity of the proposed sensing structure can be improved by using the high-order mode (<jats:inline-formula> <jats:tex-math><?CDATA ${{\rm{E}}}_{21}^{y}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi mathvariant="normal">E</mml:mi> <mml:mrow> <mml:mn>21</mml:mn> </mml:mrow> <mml:mi>y</mml:mi> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_30_11_114208_ieqn5.gif" xlink:type="simple" /> </jats:inline-formula>). The RI sensitivity for the <jats:inline-formula> <jats:tex-math><?CDATA ${{\rm{E}}}_{21}^{y}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi mathvariant="normal">E</mml:mi> <mml:mrow> <mml:mn>21</mml:mn> </mml:mrow> <mml:mi>y</mml:mi> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_30_11_114208_ieqn6.gif" xlink:type="simple" /> </jats:inline-formula> mode is ∼ 201 nm/RIU, which is twice to thrice higher than those for the <jats:inline-formula> <jats:tex-math><?CDATA ${{\rm{E}}}_{11}^{x}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi mathvariant="normal">E</mml:mi> <mml:mrow> <mml:mn>11</mml:mn> </mml:mrow> <mml:mi>x</mml:mi> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_30_11_114208_ieqn7.gif" xlink:type="simple" /> </jats:inline-formula> mode and the <jats:inline-formula> <jats:tex-math><?CDATA ${{\rm{E}}}_{11}^{y}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi mathvariant="normal">E</mml:mi> <mml:mrow> <mml:mn>11</mml:mn> </mml:mrow> <mml:mi>y</mml:mi> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_30_11_114208_ieqn8.gif" xlink:type="simple" /> </jats:inline-formula> mode. Considering a commercial spectrometer, the proposed sensing structure based on the SRTMR achieves a limit of detection (LOD) of ∼ 4.7 × 10<jats:sup>−6</jats:sup> RIU. Combined with the microfluidic channel, the SRTMR can possess wide applications in the clinical diagnostic assays and biochemical detections.</jats:p>

<jats:p>The determination of band offsets is crucial in the optimization of Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>-based devices, since the band alignment types could determine the operations of devices due to the restriction of carrier transport across the heterogeneous interfaces. In this work, the band offsets of the Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>/FTO heterojunction are studied using x-ray photoelectron spectroscopy (XPS) based on Kraut’s method, which suggests a staggered type-II alignment with a conduction band offset (Δ <jats:italic>E</jats:italic> <jats:sub>C</jats:sub>) of 1.66 eV and a valence band offset (Δ <jats:italic>E</jats:italic> <jats:sub>V</jats:sub>) of –2.41 eV. Furthermore, the electronic properties of the Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>/FTO heterostructure are also measured, both in the dark and under ultraviolet (UV) illuminated conditions (254 nm UV light). Overall, this work can provide meaningful guidance for the design and construction of oxide hetero-structured devices based on wide-bandgap semiconducting Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>.</jats:p>

<jats:p>We report experimental observations performed using a net anomalous dispersion Er-doped fiber ring laser without polarization-selective elements, highlighting the domain-wall solitary pulses generated under the incoherent polarization coupling. By adjusting the pump power and the polarization state appropriately, bright and dark solitons can stably co-exist in the cavity, both centered at 1562.16 nm with a 3-dB spectral width of ∼ 0.15 nm and a repetition rate of 3.83 MHz. Moreover, the 0.8 mm long thulium-doped fiber (TDF) facilitated the mode-locking and self-starting of the laser. This is the first demonstration of a laser being used to generate bright and dark solitons synchronously while using TDF as the saturable absorber (SA). Except possessing the all-fiber structure, the laser exhibits good stability, which may have a significant influence on improvement of the pulse-laser design, and may broaden practical applications in optical sensing, optical communication, and soliton multiplexed systems.</jats:p>

<jats:p>A theory of multiphoton photoemission is derived to explain the experimentally observed monotonic decrease with the wavelength in the electron yield of TiO<jats:sub>2</jats:sub> nanoparticles (NPs) by as large as four orders of magnitude. It is found that the fitting parameter corresponds to the energy position of Ti3d e<jats:sub>g</jats:sub> and t<jats:sub>2g</jats:sub> states, and the derived theory is a novel diagnostic of excited states in the conduction band, very importantly, applicable to individual NPs. The difference between four-photon slope NPs and three-photon slope NPs is attributed to the difference in defect density. The success of the theory in solving the puzzling result shows that thermal emission from high-lying levels may dominate over direct multiphoton ionization in solids when the photon number larger than four is required.</jats:p>

<jats:p>The phonon dispersion relations of crystalline solids play an important role in determining the mechanical and thermal properties of materials. The phonon dispersion relation, as well as the vibrational density of states, is also often used as an indicator of variation of lattice thermal conductivity with the external stress, defects, etc. In this study, a simple and fast tool is proposed to acquire the phonon dispersion relation of crystalline solids based on the LAMMPS package. The theoretical details for the calculation of the phonon dispersion relation are derived mathematically and the computational flow chart is present. The tool is first used to calculate the phonon dispersion relation of graphene with two atoms in the unit cell. Then, the phonon dispersions corresponding to several potentials or force fields, which are commonly used in the LAMMPS package to modeling the graphene, are obtained to compare with that from the DFT calculation. They are further extended to evaluate the accuracy of the used potentials before the molecular dynamics simulation. The tool is also used to calculate the phonon dispersion relation of superlattice structures that contains more than one hundred of atoms in the unit cell, which predicts the phonon band gaps along the cross-plane direction. Since the phonon dispersion relation plays an important role in the physical properties of condensed matter, the proposed tool for the calculation of the phonon dispersion relation is of great significance for predicting and explaining the mechanical and thermal properties of crystalline solids.</jats:p>

<jats:p>An efficient scheme for generating ultrabright <jats:italic>γ</jats:italic>-rays from the interaction of an intense laser pulse with a near-critical-density plasma is studied by using the two-dimensional particle-in-cell simulation including quantum electrodynamic effects. We investigate the effects of target shape on <jats:italic>γ</jats:italic>-ray generation efficiency using three configurations of the solid foils attached behind the near-critical-density plasma: a flat foil without a channel (target 1), a flat foil with a channel (target 2), and a convex foil with a channel (target 3). When an intense laser propagates in a near-critical-density plasma, a large number of electrons are trapped and accelerated to GeV energy, and emit <jats:italic>γ</jats:italic>-rays via nonlinear betatron oscillation in the first stage. In the second stage, the accelerated electrons collide with the laser pulse reflected from the foil and emit high-energy, high-density <jats:italic>γ</jats:italic>-rays via nonlinear Compton scattering. The simulation results show that compared with the other two targets, target 3 affords better focusing of the laser field and electrons, which decreases the divergence angle of <jats:italic>γ</jats:italic>-photons. Consequently, denser and brighter <jats:italic>γ</jats:italic>-rays are emitted when target 3 is used. Specifically, a dense <jats:italic>γ</jats:italic>-ray pulse with a peak brightness of 4.6 × 10<jats:sup>26</jats:sup> photons/s/mm<jats:sup>2</jats:sup>/mrad<jats:sup>2</jats:sup>/0.1%BW (at 100 MeV) and 1.8 × 10<jats:sup>23</jats:sup> photons/s/mm<jats:sup>2</jats:sup>/mrad<jats:sup>2</jats:sup>/0.1%BW (at 2 GeV) are obtained at a laser intensity of 8.5 × 10<jats:sup>22</jats:sup> W/cm<jats:sup>2</jats:sup> when the plasma density is equal to the critical plasma density <jats:italic>n</jats:italic> <jats:sub>c</jats:sub>. In addition, for target 3, the effects of plasma channel length, foil curvature radius, laser polarization, and laser intensity on the <jats:italic>γ</jats:italic>-ray emission are discussed, and optimal values based on a series of simulations are proposed.</jats:p>