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<jats:p>Conventional parameter estimation methods for pseudo-random binary code-linear frequency modulation (PRBC-LFM) signals require prior knowledge, are computationally complex, and exhibit poor performance at low signal-to-noise ratios (SNRs). To overcome these problems, a blind parameter estimation method based on a Duffing oscillator array is proposed. A new relationship formula among the state of the Duffing oscillator, the pseudo-random sequence of the PRBC-LFM signal, and the frequency difference between the PRBC-LFM signal and the periodic driving force signal of the Duffing oscillator is derived, providing the theoretical basis for blind parameter estimation. Methods based on amplitude method, short-time Fourier transform method, and power spectrum entropy method are used to binarize the output of the Duffing oscillator array, and their performance is compared. The pseudo-random sequence is estimated using Duffing oscillator array synchronization, and the carrier frequency parameters are obtained by the relational expressions and characteristics of the difference frequency. Simulation results show that this blind estimation method overcomes limitations in prior knowledge and maintains good parameter estimation performance up to an SNR of –35 dB.</jats:p>

<jats:p>High-level <jats:italic>ab initio</jats:italic> calculations of the Λ–S states for aluminum monoiodide (AlCl) molecule are performed by utilizing the explicitly correlated multireference configuration interaction (MRCI-F12) method. The Davidson correction and scalar relativistic correction are investigated in the calculations. Based on the calculation by the MRCI-F12 method, the spin–orbit coupling (SOC) effect is investigated with the state-interacting technique. The adiabatic potential energy curves (PECs) of the 13 Λ–S states and 24 Ω states are calculated. The spectroscopic constants of bound states are determined, which are in accordance with the results of the available experimental and theoretical studies. Finally, the transition properties of 0<jats:sup>+</jats:sup>(2)–X0<jats:sup>+</jats:sup>, 1(1)–X0<jats:sup>+</jats:sup>, and 1(2)–X0<jats:sup>+</jats:sup> transitions are predicted, including the transition dipole moments (TDMs), Franck–Condon factors (FCFs), and the spontaneous radiative lifetimes.</jats:p>

<jats:p>The energy levels, transition energies, transition probabilities, weighted oscillator strengths, and line strengths of Li-like ions (<jats:italic>Z</jats:italic> = 7–11) in dense plasmas are investigated in this work. The relativistic effects and electron correlation effects are described by the MCDHF method. The ion sphere model is applied to include the dense plasma screening effect. The ground configuration 1s<jats:sup>2</jats:sup>2s and the excited 1s<jats:sup>2</jats:sup>2p, 1s<jats:sup>2</jats:sup>3<jats:italic>l</jats:italic> (<jats:italic>l</jats:italic> = 0–2) are considered. The configuration sets are enlarged until <jats:italic>n</jats:italic> = 7 where the calculated energy levels have converged. The critical free electron densities of 1s<jats:sup>2</jats:sup>3d states are estimated. Except for 1s<jats:sup>2</jats:sup>3s–1s<jats:sup>2</jats:sup>3p transitions, the transition energies for Δ <jats:italic>n</jats:italic> = 0 increase, and for Δ <jats:italic>n</jats:italic> ≠ 0 decrease with increasing free electron densities. For 1s<jats:sup>2</jats:sup>3s–1s<jats:sup>2</jats:sup>3p transitions, the spectra show blue-shift at lower free electron densities and red-shift at higher free electron densities, and the energy level crossing phenomens are observed at higher free electron densities.</jats:p>

<jats:p>The exciton Stark shift and polarization in hemispherical quantum dots (HQDs) each as a function of strength and orientation of applied electric field are theoretically investigated by an exact diagonalization method. A highly anisotropic Stark redshift of exciton energy is found. As the electric field is rotated from Voigt to Faraday geometry, the redshift of exciton energy monotonically decreases. This is because the asymmetric geometric shape of the hemispherical quantum dot restrains the displacement of the wave function to the higher orbital state in response to electric field along Faraday geometry. A redshift of hole energy is found all the time while a transition of electron energy from this redshift to a blueshift is found as the field is rotated from Voigt to Faraday geometry. Taking advantage of the diminishing of Stark effect along Faraday geometry, the hemispherical shapes can be used to improve significantly the radiative recombination efficiency of the polar optoelectronic devices if the strong internal polarized electric field is along Faraday geometry.</jats:p>

<jats:p>Inspired by a recent experiment [<jats:italic>Phys. Rev. Lett.</jats:italic> <jats:bold>122</jats:bold> 253201(2019)] that an unprecedented quantum interference was observed in the way of stimulated Raman adiabatic passage (STIRAP) due to the coexisting resonant- and detuned-STIRAPs, we comprehensively study this effect. Our results uncover the scheme robustness towards any external-field fluctuations coming from laser intensity noise and imperfect resonance condition, as well as the persistence of high-contrast interference pattern even when more nearby excited levels are involved. We verify that an auxiliary dynamical phase accumulated in hold time caused by the presence of the quasi-dark state in detuned-STIRAP can sensitively manipulate the visibility and frequency of the interference pattern, representing a new hallmark to measure the hyperfine energy accurately. The robust stability of the scheme comes from the intrinsic superiority embedded in the STIRAP mechanism that preserves the coherence of population transfer, which promises a remarkable performance of quantum interference in a practical implementation.</jats:p>

<jats:p>Micromotion induced by the radio-frequency field contributes greatly to the systematic frequency shifts of optical frequency standards. Although different strategies for mitigating this effect have been proposed, trapping ions optically has the potential to provide a generic solution to the elimination of micromotion. This could be achieved by trapping a single ion in the dipole trap composed of a highpower laser field. Here, we present the setup of the dipole trap composed of a 532 nm laser at a power of 10 W aiming to optically trap a single <jats:sup>40</jats:sup>Ca<jats:sup>+</jats:sup> and we observe an AC-Stark shift of the fluorescence spectrum line of ∼22 MHz caused by the 532 nm dipole beam. The beam waist of the dipole laser is several microns, which would provide a dipole potential strong enough for all-optical trapping of a single <jats:sup>40</jats:sup>Ca<jats:sup>+</jats:sup> ion.</jats:p>

<jats:p>We propose a scheme in which an arbitrary incidence can be made perfectly reflected/transmitted with a phase modulator. We analyze the variation of intracavity field as well as output field with closed-loop phase <jats:italic>ϕ</jats:italic> <jats:sub>1</jats:sub> of the control fields and relative phase <jats:italic>ϕ</jats:italic> <jats:sub>2</jats:sub> of the probe beams. With two phases, medium absorption and light interference can be controlled so that photon escape from the cavity can be manipulated, thus an intensity switching based on phase modulation can be realized. And the condition for perfect transmitter or reflector is obtained. Then based on the transmission/reflection analysis, the total absorption of this system can be investigated. Therefore our scheme can be used as an absorption interferometer to explore the optical absorption in some complicated system. The state delay of the output light intensity, which is dependent on <jats:italic>ϕ</jats:italic> <jats:sub>1</jats:sub> or <jats:italic>ϕ</jats:italic> <jats:sub>2</jats:sub>, can be applied in the realization of quantum phase gate and subtle wave filter. And based on this scheme, we implement the state transfer between perfect transmitter/reflector and non-perfect coherent photon absorber via relative-phase modulation.</jats:p>

<jats:p>A new pressure-calibration method for calibrating the reduction of second harmonic (2<jats:italic>f</jats:italic>) amplitude caused by pressure broadening effect in sealed microbial growth environment is present. The new method combines with linewidth compensation and modulation depth compensation and makes the 2<jats:italic>f</jats:italic> amplitude accurately retrieve metabolic CO<jats:sub>2</jats:sub> in microbial growth. In order to verify the method, a simulation experiment is developed, in which the increasing CO<jats:sub>2</jats:sub> concentration leads to the increasing pressure. Comparing with the relation between the traditional 2<jats:italic>f</jats:italic> amplitude and gas concentration, there is a monotonous relation between the calibrated 2<jats:italic>f</jats:italic> amplitude and CO<jats:sub>2</jats:sub> concentration, particularly, a linear relation is present when the CO<jats:sub>2</jats:sub> concentration is replaced with the CO<jats:sub>2</jats:sub> particle number. In terms of microbial measurement, the growth of <jats:italic>Escherichia coli</jats:italic> is measured, and the culture bottle is sealed during the microbial growth process. The experimental results show that, comparing to the microbial growth retrieved by traditional 2<jats:italic>f</jats:italic> amplitude, the calibrated 2<jats:italic>f</jats:italic> amplitude can accurately retrieve microbial growth in sealed environment.</jats:p>

<jats:p>We propose and demonstrate a passively mode-locked erbium-doped fiber laser (EDFL) based on zinc-oxide/polydimethylsiloxane (ZnO/PDMS) saturable absorber (SA) that evanescently interacts with the light on a tapered fiber. The ZnO/PDMS composite is coated on the whole surface of the tapered fiber to guarantee the maximum efficiency of the SA device, with a measured insertion loss of 0.87 dB and a modulation depth of 6.4%. The proposed laser can generate soliton mode-locking operation at a threshold power of 33.07 mW. The generated output pulse yields a repetition rate and pulse width of 9.77 MHz and 1.03 ps, respectively. These results indicate that the proposed ZnO/PDMS-clad tapered fiber could be useful as an efficient, compatible, and low-cost SA device for ultrafast laser applications.</jats:p>

<jats:p>We experimentally demonstrated a stable multi-wavelength bright–dark pulse pair in a mode-locked thulium-doped fiber laser (TDFL). The nonlinear polarization rotation (NPR) and nonlinear optical loop mirror (NOLM) were employed in a figure-eight cavity to allow for multi-wavelength mode-locking operation. By incorporating different lengths of high birefringence polarization-maintaining fiber (PMF), the fiber laser could operate stably in a multi-wavelength emission state. Compared with the absence of the PMF, the birefringence effect caused by PMF resulted in rich multi-wavelength optical spectra and better intensity symmetry and stability of the bright–dark pulse pair.</jats:p>