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<jats:p>The mass- and field-shift parameters of the two 2s <jats:sup>2</jats:sup>S<jats:sub>1/2</jats:sub> → 2p <jats:sup>2</jats:sup>P<jats:sub>1/2,3/2</jats:sub> transitions in the Li-like Ca ions are calculated by using multi-configuration Dirac–Hartree–Fock (MCDHF) and the relativistic configuration interaction (RCI) methods with the inclusion of the transverse photon (Breit) interaction, vacuum polarization and self-energy corrections. In addition, the mass shift and field shift of these two transitions are calculated, where the field shift is calculated by using the evaluated value <jats:italic>δ</jats:italic>〈 <jats:italic>r</jats:italic> <jats:sup>2</jats:sup>〉 obtained by [<jats:italic>Atomic Data and Nuclear Data Tables</jats:italic> <jats:bold>99</jats:bold> 69 (2013)]. It is found that the mass shift of Li-like Ca ions is greater than the field shift.</jats:p>

<jats:p>Based on the fully relativistic multiconfiguration Dirac–Hartree–Fock (MCDHF) method and the corresponding program package GRASP2018, a new program for calculating the polarizabilities is developed. As the first application, the static electric-dipole polarizabilities of the ground state 2s<jats:sup>2</jats:sup> <jats:sup>1</jats:sup> <jats:italic>S</jats:italic> <jats:sub>0</jats:sub> and excited state 2s2p <jats:sup>3</jats:sup> <jats:italic>P</jats:italic> <jats:sub>0</jats:sub> of beryllium are calculated. By means of these polarizabilities, the blackbody radiation (BBR) shift of the 2s2p <jats:sup>3</jats:sup> <jats:italic>P</jats:italic> <jats:sub>0</jats:sub> → 2s<jats:sup>2</jats:sup> <jats:sup>1</jats:sup> <jats:italic>S</jats:italic> <jats:sub>0</jats:sub> clock transition is determined. The present results agree very well with other available theoretical results.</jats:p>

<jats:p>In the troposphere, the destruction of ozone and the formation of new particles are closely related to the iodine content, which mainly comes from iodide (I<jats:sup>−</jats:sup>) and iodate (<jats:inline-formula> <jats:tex-math> <?CDATA ${{\rm{IO}}}_{3}^{-}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mrow> <mml:mi mathvariant="normal">IO</mml:mi> </mml:mrow> <mml:mn>3</mml:mn> <mml:mo>−</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_30_4_043301_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>) in the seawater. Therefore, understanding the interactions between I<jats:sup>−</jats:sup>, <jats:inline-formula> <jats:tex-math> <?CDATA ${{\rm{IO}}}_{3}^{-}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mrow> <mml:mi mathvariant="normal">IO</mml:mi> </mml:mrow> <mml:mn>3</mml:mn> <mml:mo>−</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_30_4_043301_ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> and water molecules plays a certain role in alleviating the destruction of the ozone layer. Raman spectroscopy is commonly used to obtain the information of the interaction between I<jats:sup>−</jats:sup>, <jats:inline-formula> <jats:tex-math> <?CDATA ${{\rm{IO}}}_{3}^{-}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mrow> <mml:mi mathvariant="normal">IO</mml:mi> </mml:mrow> <mml:mn>3</mml:mn> <mml:mo>−</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_30_4_043301_ieqn3.gif" xlink:type="simple" /> </jats:inline-formula> and water molecules quickly and accurately. Herein, the effect of I<jats:sup>−</jats:sup> and <jats:inline-formula> <jats:tex-math> <?CDATA ${{\rm{IO}}}_{3}^{-}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mrow> <mml:mi mathvariant="normal">IO</mml:mi> </mml:mrow> <mml:mn>3</mml:mn> <mml:mo>−</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_30_4_043301_ieqn4.gif" xlink:type="simple" /> </jats:inline-formula> on the change in Raman band characteristics of water is investigated to reflect the associated intermolecular interactions change. With the addition of the two ions, the Raman band corresponding to OH stretching vibration moves towards the high wavenumber, indicating the formation of hydration structure. The narrowing of the Raman band from OH stretching vibration under weak hydrogen bond agrees well with the hydrogen bond variation, while the abnormal broadening of the Raman band from OH stretching vibration under strong hydrogen bond indicates the formation of H-down structure. With the increase of ions concentration, the frequency shift of the Raman band from OH stretching vibration under both weak and strong hydrogen bonds becomes more apparent. Meanwhile, the frequency shift of I<jats:sup>−</jats:sup> is more obvious than that of <jats:inline-formula> <jats:tex-math> <?CDATA ${{\rm{IO}}}_{3}^{-}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mrow> <mml:mi mathvariant="normal">IO</mml:mi> </mml:mrow> <mml:mn>3</mml:mn> <mml:mo>−</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_30_4_043301_ieqn5.gif" xlink:type="simple" /> </jats:inline-formula>, which indicates that I<jats:sup>−</jats:sup> is more likely to form the hydration structure with water than <jats:inline-formula> <jats:tex-math> <?CDATA ${{\rm{IO}}}_{3}^{-}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mrow> <mml:mi mathvariant="normal">IO</mml:mi> </mml:mrow> <mml:mn>3</mml:mn> <mml:mo>−</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_30_4_043301_ieqn6.gif" xlink:type="simple" /> </jats:inline-formula>. These results contribute to analyzing the different interactions between I<jats:sup>−</jats:sup>–water and <jats:inline-formula> <jats:tex-math> <?CDATA ${{\rm{IO}}}_{3}^{-}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mrow> <mml:mi mathvariant="normal">IO</mml:mi> </mml:mrow> <mml:mn>3</mml:mn> <mml:mo>−</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_30_4_043301_ieqn7.gif" xlink:type="simple" /> </jats:inline-formula>–water, then helping to prevent ozone depletion.</jats:p>

<jats:p>We analytically and numerically study the local dynamical characteristics of the Bessel beams reflected from an air—glass interface near the Brewster angle. A Taylor series expansion based on the angular spectrum component is applied to correct the reflection coefficients near the Brewster angle. Using a hybrid angular spectrum representation and vector potential method, the explicit expressions for the electric and magnetic field components of the reflected Bessel beams are derived analytically under paraxial approximation. The local energy, momentum, spin, and orbital angular momentum of the Bessel beams upon reflection near the Brewster angle are examined numerically by utilizing a canonical approach. Numerical simulation results show that the properties of these dynamical quantities for the Bessel beams near Brewster angle incidence change abruptly, and are significantly affected by their topological charge, half-cone angle, and polarization state. The present study has its importance in understanding the dynamical aspects of optical beams with vortex structure and diffraction-free nature during the reflection process.</jats:p>

<jats:p>Fresnel incoherent correlation holography (FINCH) is a unique three-dimensional (3D) imaging technique which has the advantages of scanning-free, high resolution, and easy matching with existing mature optical systems. In this article, an incoherent digital holographic spectral imaging method with high accuracy of spectral reconstruction based on liquid crystal tunable filter (LCTF) and FINCH is proposed. Using the programmable characteristics of spatial light modulator (SLM), a series of phase masks, none of whose focal lengths changes with wavelength, is designed and made. For each wavelength of LCTF output, SLM calls three phase masks with different phase constants at the corresponding wavelength, and CCD records three holograms. The spectral images obtained by this method have a constant magnification, which can achieve pixel-level image registration, restrain image registration errors, and improve spectral reconstruction accuracy. The results show that this method can not only obtain the 3D spatial information and spectral information of the object simultaneously, but also have high accuracy of spectral reconstruction and excellent color reproducibility.</jats:p>

<jats:p>This study is to report a ZnSe quantum dot with a large two-photon absorption cross section and good biocompatibility, which can be used in bioimaging. Fluorescence emission at 410 nm is observed in the quantum dot under 760-nm laser excitation. These biocompatible quantum dots exhibit a two-photon cross-section of 9.1 × 10<jats:sup>5</jats:sup> GM (1 GM = 10<jats:sup>−50</jats:sup> cm<jats:sup>4</jats:sup>⋅s/photon). Two-photon excited laser scanning microscopic images show that cells co-cultured with ZnSe quantum dots are found in the blue channel at a fluorescence intensity that is 14.5 times that of control cells not co-cultured with quantum dots. After incubating zebrafish larvae with ZnSe quantum dots for 24 h, the fluorescence intensity of the yolk sac stimulated by ultraviolet light is 2.9 times that of the control group. The proposed material shows a great potential application in biological imaging.</jats:p>

<jats:p>We present the design and fabrication of a novel dual-function high contrast gratings that can be used as a polarization-selective beam splitter with transverse magnetic polarization, which performs two independent functions, <jats:italic>i.e.</jats:italic>, reflection focusing and power equalization at a wavelength of 1550 nm. This dual-function grating profile is optimized by the rigorous coupled-wave analysis and the finite-element method. Simple analytical expressions of phase and modal guideline for the beam splitter design are given. The beam splitter based on the grating structure is experimentally studied at a distance of 160 μm from the reflection plane, the results are consistent with the theoretical results basically.</jats:p>

<jats:p>Aiming at the problem of scanning distortion in <jats:italic>X</jats:italic>–<jats:italic>Y</jats:italic> galvanometer light detecting and ranging (Lidar) scanning system, we propose a method of image scanning distortion correction with controllable driving voltage compensation. Firstly, the geometrical optics vectors model is established to explain the principle of pincushion distortion in the galvanometer scanning system, and the simulation result of scanning trajectory is consistent with experiments. The linear relationship between the driving voltage and the scanning angle of the galvanometer is verified. Secondly, the relationship between the deflection angle of the galvanometer and the scanning trajectory and the driving voltage is deduced respectively, and an image scanning correction algorithm with controllable driving voltage compensation is obtained. The simulation experiment results of the proposed method show that the root-mean-square error (RMSE) and the corresponding curve between the scan value and the actual value at different distances, have a good correction effect for the pincushion distortion. Finally, the <jats:italic>X</jats:italic>–<jats:italic>Y</jats:italic> galvanometer scanning Lidar system is established to obtain undistorted two-dimensional scanned image and it can be applied to the three-dimensional Lidar scanning system in the actual experiments, which further demonstrates the feasibility and practicability of our method.</jats:p>

<jats:p>We propose a core rotation-sensing element for improving the sensitivity of the micro-optical gyroscope using the large nonreciprocal effect with a photonic crystal. The sharp transmission peak of electromagnetically induced transparency in photonic crystal generated from a periodic distribution of cold atoms is sensitive to the rotation. Our numerical results show that the sensitivity of relative rotation is about 50 times higher and the sensitivity of absolute rotation is more than two orders higher than that of the traditional resonant optical gyroscope. Also, the sensitivity of the gyroscope can be manipulated by varying the atomic density, modulation frequency, probe pulse width, and photonic crystal length, etc.</jats:p>

<jats:p>Our recently proposed three-step method showed the promising potential to improve the accuracy of relative wavelength response (RWR) characterization in the wavelength-modulation spectroscopy (WMS) over the commonly used summation method. A detailed comparison of the three-step method and the summation method, for the wavelength-scanned WMS gas-sensing, was performed with different laser parameters (modulation indexes and scan indexes) and gas properties (pressures and concentrations). Simulation results show that the accuracy of the predicted gas parameters is strongly limited by the RWR characterization with large modulation index and high gas pressure conditions. Both fitting residuals of RWR and errors of predicted gas parameters from the recently proposed three-step method are nearly 2 orders of magnitude smaller than those from the summation method. In addition, the three-step method is further improved by introducing a coupling term for the 2<jats:sup>nd</jats:sup> harmonic amplitude. Experiments with CO<jats:sub>2</jats:sub> absorption transition at 6976.2026 cm<jats:sup>−1</jats:sup> were conducted and validated the simulation analysis. The modified-three-step method presents an improved accuracy in RWR description with at least 5% smaller fitting residual for all conditions compared with the three-step method, although the deviation of the deduced CO<jats:sub>2</jats:sub> concentrations between these two methods does not exceed 0.2%.</jats:p>