Catálogo de publicaciones - revistas

<jats:p>A scheme is used to explore the behavior of three-dimensional (3D) atom localization in a Y-type hot atomic system. We can obtain the position information of the atom due to the position-dependent atom–field interaction. We study the influences of the system parameters and the temperature on the atom localization. More interestingly, the atom can be localized in a subspace when the temperature is equal to 323 K. Moreover, a method is proposed to tune multiparameter for localizing the atom in a subspace. The result is helpful to achieve atom nanolithography, photonic crystal and measure the center-of-mass wave function of moving atoms.</jats:p>

<jats:p>Taking into account the dephasing process in the realistic atomic ensemble, we theoretically study the generation of atomic spin squeezing via atomic coherence induced by the coupling and probe fields. Using the Heisenberg–Langevin approach, we find that the perfect spin squeezing in the <jats:italic>X</jats:italic> component can be obtained while the coupling and probe fields produce the maximum coherence between the ground state sublevels 1 and 2. Moreover, the degree of atomic spin squeezing in the <jats:italic>X</jats:italic> component can be strengthened with the increasing atomic density and/or Rabi frequency of the mixing field. The theoretical results provide a proof-of-principle demonstration of generating the atomic spin squeezing via quantum coherence in the realistic atomic ensemble which may find potential applications in quantum information processing and quantum networks.</jats:p>

<jats:p>We design and construct a resonant photodetector (RPD) with a <jats:italic>Q</jats:italic> factor of 320.83 at the resonant frequency of 38.5 MHz on the basis of a theoretical analysis. Compared with the existing RPD under the same conditions, the signal-to-noise-ratio of the error signal is increased by 15 dB and the minimum operation power is reduced from −55 dBm to −70 dBm. By comparing the standard deviations of the stability curves, we confirm that the RPD has a dramatic improvement on ultralow power extraction. In virtue of the RPD, we have completed the demonstration of channel multiplexing quantum communication.</jats:p>

<jats:p>We propose a three-cavity coupled cavity optomechanical (COM) structure with tunable system parameters and theoretically investigate the probe-light transmission rate. Numerical calculation of the system’s spectra demonstrates distinctive compound-induced transparency (CIT) characteristics, including multiple transparency windows and sideband dips, which can be explained by a coupling between optomechanically-induced transparency (OMIT) and electromagnetically-induced transparency. The effects of optical loss (gain) in the cavity, number and topology of active cavity, tunneling ratio, and pump laser power on the CIT spectrum are evaluated and analyzed. Moreover, the optical group delay of CIT is highly controllable and fast–slow light inter-transition can be achieved. The proposed structure makes possible the advantageous tuning freedom and provides a potential platform for controlling light propagation and fast–slow light switching.</jats:p>

<jats:p>Ultrafast laser filament-induced breakdown spectroscopy (FIBS) is a potential technique for quantitative analysis of trace elements. In this work, we investigate the effect of the distance between focusing lens and target surface on the FIBS quantitative analysis of Mn element in aluminum alloys, and several major parameters are calculated such as the linear correlation coefficient (<jats:italic>R</jats:italic> <jats:sup>2</jats:sup>), limits of detection (LOD), relative standard deviation (RSD), and root-mean-square error of cross-validations (RMSECV). The results show that the quantitative analysis parameter values before and after filament position are different. The optimal value can be obtained at the filament region, the average values of total 23 positions of <jats:italic>R</jats:italic> <jats:sup>2</jats:sup>, LOD, RSD, and RMAECV were 99.45%, 1.41 mg/kg, 7.12%, and 0.56%, respectively. Besides, the spatial distributions of quantitative analysis parameter values in filament region are noticeable, and this is essentially due to intensity clamping effect in a filament.</jats:p>

<jats:p>Decoherence of fiber laser sources is of great importance in imaging applications, and most current studies use ordinary multi-mode fibers (MMFs). Here, a newly designed single-trench fiber (STF) is investigated to reduce the spatial coherence of fiber light source and compared with MMFs. By bending two fibers with different turns, speckle contrast of a 0.8-m-long STF can be reduced from 0.13 to 0.08, while a 0.8-m-long MMF shows an inverse result. Through speckle contrast and decoupling-mode analysis, the reason of this inverse trend is revealed. Firstly, the STF supports more modes than the MMF due to its larger core diameter. Secondly, mode leak from the first core of the STF can couple to the second core when bending the STF. Thus, power distribution among high and low-order modes become more even, reducing the spatial coherence considerably. However, in the MMF, high-order modes become leaky modes and decrease slightly when bending the fiber. This work provides a new method to modulate coherence of light source and a new angle to study decoherence principle using special fibers.</jats:p>

<jats:p>The Stokes polarimeter based on liquid crystal variable retarders (LCVRs) is envisaged as a promising novel technique for polarization measurement in space applications due to the inherent advantage of eliminating the need for conventional rotating polarizing optics and increasing the measuring speed. However, the intrinsic multi-beam interference in LCVRs limits its polarization accuracy by several percent. How to eliminate the influence of the interference effect becomes an urgent issue for the liquid-crystal-based Stokes polarimeter. The present study introduces a simplified but effective interference model based on the thin-film optics and polarized light theory to simulate the relationship between the interference effect of the LCVRs-based Stokes polarimeter and the polarization accuracy. The simulation results show that the transmittance variation of LCVR with the derived voltage is caused by multi beam interference between the indium tin oxide (ITO) film and the liquid crystal within LCVR, which produces a few percent of instrumental polarization. The instrumental polarization is about 0.01 and different for different wavelengths. An optimization method was proposed to reduce the instrumental polarization to 0.002, effectively improving the polarization sensitivity of the Stokes polarimeter limited by the interference. In addition, an experimental setup was built up to measure and analyze the influence of the interference effect of the LCVRs-based Stokes polarimeter on the polarization accuracy before and after the optimization. The experiment results are in good agreement with the simulation.</jats:p>

<jats:p>To measure the equivalent ratio distribution of the two-stage lean premixed (DLP) flame, we propose using acetone/toluene planar laser-induced fluorescence (PLIF) technology to simultaneously measure the concentrations of the two components. Appropriate excitation laser wavelength and filters are used to assess the influence of acetone and toluene on each other’s fluorescence signal at room temperature. Experimental results show that acetone has a strong absorption effect on toluene’s fluorescence signal, the effective absorption cross-section is 5.77 × 10<jats:sup>−20</jats:sup> cm<jats:sup>−2</jats:sup>. Acetone has an obvious quenching effect on the toluene fluorescence signal, and the Stern–Volmer coefficient is 0.50 kPa<jats:sup>−1</jats:sup>. The collisions between the molecules of toluene and acetone will lead to the enhancement of the fluorescence signal of acetone, and the enhancement coefficient is exponential with the acetone’s concentration. The quantitative relationship between the fluorescence intensity and the concentrations of the two tracers is obtained by establishing the photophysical model of toluene and acetone’s fluorescence signals.</jats:p>

<jats:p>We theoretically introduce two new photon-modulated atomic coherent states (ACSs) via using the Schwinger bosonic representation of the angular momentum operators (the sequential operations <jats:inline-formula> <jats:tex-math><?CDATA ${J}_{\pm }^{n}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>J</mml:mi> <mml:mo>±</mml:mo> <mml:mi>n</mml:mi> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_29_12_124213_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>) on an ACS, and investigate their nonclassicality using the Wigner distribution, photon number distribution, and entanglement entropy. It is found that photon-modulated ACSs possess more stronger nonclassicality than the original ACS in certain regions of <jats:italic>τ</jats:italic>, the nonclassicality enhances with increasing number <jats:italic>n</jats:italic> of the operations <jats:italic>J</jats:italic> <jats:sub>±</jats:sub> and the operation <jats:inline-formula> <jats:tex-math><?CDATA ${J}_{+(-)}^{n}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>J</mml:mi> <mml:mrow> <mml:mo>+</mml:mo> <mml:mo stretchy="false">(</mml:mo> <mml:mo>−</mml:mo> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> <mml:mi>n</mml:mi> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_29_12_124213_ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> enhances the entanglement in the region of small (large) <jats:italic>τ</jats:italic>.</jats:p>

<jats:p>Fluid-conveying pipe systems are widely used in various equipments to transport matter and energy. Due to the fluid–structure interaction effect, the fluid acting on the pipe wall is easy to produce strong vibration and noise, which have a serious influence on the safety and concealment of the equipment. Based on the theory of phononic crystals, this paper studies the vibration transfer properties of a locally resonant (LR) pipe under the condition of fluid–structure interaction. The band structure and the vibration transfer properties of a finite periodic pipe are obtained by the transfer matrix method. Further, the different impact excitation and fluid–structure interaction effect on the frequency range of vibration attenuation properties of the LR pipe are mainly considered and calculated by the finite element model. The results show that the existence of a low-frequency vibration bandgap in the LR pipe can effectively suppress the vibration propagation under external impact and fluid impact excitation, and the vibration reduction frequency range is near the bandgap under the fluid–structure interaction effect. Finally, the pipe impact experiment was performed to verify the effective attenuation of the LR structure to the impact excitation, and to validate the finite element model. The research results provide a technical reference for the vibration control of the fluid-conveying pipe systems that need to consider blast load and fluid impact.</jats:p>