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COVER ARTICLE

  

COVER ARTICLE

Photon blockade effect in giant atom-coupled triple-cavity system
LUO Junhao, MA Kangjie, LIANG Yan, SHENG Zhijun, SUN Yiding, TAN Lei
2025, 74 (21): 214202. doi: 10.7498/aps.74.20251000
Abstract +
The photon blockade effects in a system consisting of an artificial giant atom coupled with three cavities are investigated. By solving the Schrödinger equation, we obtain the steady-state probability amplitudes of the system and derive the analytical expressions for the equal-time second-order correlation function. Based on these analytical expressions, the optimal conditions for achieving the photon blockade under different driving conditions are derived in detail.We first examine the energy spectra and transition pathways for the single-photon and two-photon excitations in weakly driven cavity mode, and then investigate the statistical properties of photons. It is demonstrated that the optimal conventional photon blockade can be achieved by selecting appropriate driving detuning as characterized by the equal-time second-order correlation function of $g^{\left(2\right)}\left(0\right)\approx{10}^{-3.4} $. Remarkably, we observe that both cavities of the system exhibit robust photon blockade effects against the weak driving. It is also found that with the increase of the coupling strength between the artificial giant atom and cavities, the photon blockade phenomenon becomes more pronounced while maintaining its robustness to the weak driving. Furthermore, we consider the case of simultaneously driving both the artificial giant atom and cavity modes. The unique multi-point coupling characteristics of the artificial giant atom provide additional transition pathways for photons, thereby allowing us to use the resulting quantum interference to further enhance photon blockade. When the system satisfies the optimal parametric conditions for both the conventional and unconventional photon blockade effects, one cavity exhibits exceptional photon blockade with $g^{\left(2\right)}\left(0\right)\approx{10}^{-6.5} $.This research greatly relaxes the stringent parameter requirements for the experimental realization of single-photon sources and provides a theoretical support for improving their quality, which is crucial for achieving high-performance single-photon sources.

SPECIAL TOPIC—Technology of magnetic resonance

  

EDITOR'S SUGGESTION

Near-zero-field nuclear magnetic resonance and hyperpolarization technology
LI Zeming, LV Yunxi, QI Haogang, QU Qianyue, TAN Zheng, WANG Li, JIANG Weiping, HU Yinan, ZHOU Xin
2025, 74 (21): 218701. doi: 10.7498/aps.74.20250771
Abstract +
Near-zero-field nuclear magnetic resonance (NMR) has become a rapidly developing spectroscopic and imaging method, providing promising opportunities for portable diagnostics and fast chemical analysis. A key technology is the atomic magnetometer, and its ongoing improvements have sparked growing interest in potential clinical applications.The near-zero-field NMR has long been limited by weak signal strength, but recent developments in the hyperpolarization method have provided an effective solution to this problem. Dissolution dynamic nuclear polarization (dDNP), parahydrogen-based polarization schemes (PHIP/SABRE), chemically induced dynamic nuclear polarization (CIDNP), and spin-exchange optical pumping (SEOP) have all demonstrated preliminary feasibility in this context.By combining such hyperpolarization strategies with near-zero-field detection, strong signals can be obtained without the need of traditional high-field magnets. This capability opens new pathways for applying near-zero-field NMR to both chemical sensing and biomedical imaging, enabling compact tools for rapid analysis and diagnostic applications. Here, we review the recent progress of the intersection of near-zero-field NMR and hyperpolarization techniques.

SPECIAL TOPIC—Quantum information processing

  

EDITOR'S SUGGESTION

Latest research progress of quantum identity authentication
WANG Xingfu, ZHENG Yanyan, GU Shipu, ZHANG Qi, ZHONG Wei, DU Mingming, LI Xiyun, SHEN Shuting, ZHANG Anlei, ZHOU Lan, SHENG Yubo
2025, 74 (21): 210302. doi: 10.7498/aps.74.20250920
Abstract +
The absolute security of quantum communication protocols relies on a critical premise: all participating parties are legitimate users. Ensuring the legitimacy of participant identities is paramount in complex real-world communication environments. Quantum identity authentication (QIA), in which fundamental principles of quantum mechanics are used to achieve unilateral or mutual authentication between communicating parties, constitutes an indispensable core component for building a comprehensive quantum secure communication system. It holds significant research value in the field of quantum communication.This review employs a comparative classification method to systematically outline the research trajectory of QIA protocols. By categorizing protocols based on the required quantum resources and the types of quantum protocols employed, the advantages and disadvantages of various categories are analyzed in terms of efficiency, security, and practicality. Single-photon protocols require low resources, and they are easy to implement, and compatible with existing optical components, but require high-efficiency single-photon detectors and exhibit weak noise resistance. Entangled-state protocols offer high security and strong resistance to eavesdropping, particularly suitable for long-distance or multi-party authentication. However, they greatly depend on the preparation and maintenance of high-precision, stable multi-particle entanglement sources, resulting in high experimental complexity. Continuous-variable (CV) protocols achieve high transmission efficiency in short-distance metropolitan area networks and are compatible with classical optical communication equipment, making experiments relatively straightforward. Yet, they require high-precision modulation technology and are sensitive to channel loss. Hybrid protocols aim to balance resource efficiency and security while reducing reliance on a single quantum source, but their design is complex and may introduce new attack vectors. Quantum key distribution (QKD) framework protocols embed identity authentication in the key distribution process, making them suitable for scenarios requiring long-term secure key distribution, although they often depend on pre-shared keys or trusted third parties. Quantum secure direct communication (QSDC) framework protocols integrate authentication with secure direct information transmission, offering high efficiency for real-time communication, but requiring high channel quality. Measurement-device-independent QSDC (MDI-QSDC) represents a key development direction that can resist attacks on measurement devices. Quantum teleportation (QT) framework protocols achieves cross-node authentication and unconditional security, making it suitable for quantum relay networks despite its high experimental complexity. The entanglement swapping framework protocol can resist conspiracy attacks and is suitable for multi-party joint scenarios, but it consumes a lot of resources and relies on trusted third party. Ping-pong protocol framework supports dynamic key updates and exhibits strong resistance to eavesdropping, making it suitable for temporary authentication on mobile terminals, although it typically only supports unilateral authentication and requires a bidirectional channel.Subsequently, this review details the latest QIA protocols of our research group, including a multi-party synchronous identity authentication protocol based on Greenberger-Horne-Zeilinger (GHZ) states, and a tripartite QSDC protocol with identity authentication capabilities utilizing polarization-spatial super-coding. The GHZ-based multi-party synchronous authentication protocol leverages the strong correlations inherent in GHZ states to achieve simultaneous authentication among multiple parties. Through a carefully designed two-round decoy-state detection mechanism, it effectively resists both external eavesdropping and internal attacks originating from authenticated users, thereby enhancing the efficiency and security of identity management in large-scale quantum networks. The core innovation of the polarization-spatial super-coding tripartite QSDC protocol lies in its deep integration of the authentication process with information transmission by utilizing the spatial degrees of freedom of single photons. This design accomplishes the identity verification of two senders and the transmission of secret information within a single protocol run, ensuring end-to-end security through a three-stage security check. This “authentication-as-communication” paradigm significantly improves the overall efficiency and practicality of the protocol. Its successful implementation also relies on advancements in quantum memory technology.Finally, the review outlines future research directions for quantum identity authentication and explores its potential applications in quantum communication. The QIA research needs to focus on reducing resource dependency, exploring more efficient protocol designs, further enhancing protocol integration and robustness, prioritizing the development of protocols adaptable to real-world environments, and actively investigating integration with novel scenarios. This comprehensive review aims to provide theoretical research foundations and technical support for the practical development of future quantum identity authentication.

SPECIAL TOPIC—Ultrafast physics in atomic, molecular and optical systems

  

EDITOR'S SUGGESTION

Revisiting near-threshold photoelectron interference in argon with a non-adiabatic semiclassical model
TAO Jianfei, JIN Xin, WU Kefei, LIU Xiaojing
2025, 74 (21): 213201. doi: 10.7498/aps.74.20250999
Abstract +
Purpose: The interaction of intense, ultrashort laser pulses with atoms gives rise to rich non-perturbative phenomena, which are encoded within the final-state photoelectron momentum distribution (PMD). A particularly enigmatic feature often observed in the multiphoton ionization regime (Keldysh parameter $ \gamma \gtrsim 1 $), is a complex, fan-like interference pattern in the near-threshold, low-energy region of the PMD. The physical origin of this structure has been a subject of extensive debate, with proposed mechanisms ranging from multipath interference in the Coulomb field to complex sub-barrier dynamics. This work aims to provide a physical explanation for this phenomenon. We hypothesize and demonstrate that this fan-like structure is not only the consequence of Coulomb focusing, but also a direct and sensitive signature of non-adiabatic dynamics occurring as an electron tunnels through the laser-dressed atomic potential barrier. Our goal is to clearly separate the key physical ingredients responsible for shaping this quantum interference. Methodology: To achieve this, we employ a synergistic three-pronged approach that combines experiment, exact numerical simulation, and a sophisticated theoretical model.1. Experiment: We perform velocity-map imaging measurements on argon atoms ionized by a 798-nm 35-fs laser pulse at a peak intensity of $ 6.3 \times 10^{13} $ W/cm2, and the experimental results clearly show the low-energy fan-like interference pattern.2. Quantum Benchmark: We solve the time-dependent Schrödinger equation (TDSE) within the single-active-electron (SAE) approximation by using a well-established model potential for argon, which accurately reproduces its ionization potential and ground-state properties. After performing a focal-volume average to simulate experimental conditions, the TDSE results show excellent qualitative agreement with the measurements, establishing the TDSE as a reliable quantum benchmark for our investigation.3. Semiclassical Model (CTMC-p): The core of our analysis relies on a custom-developed semiclassical trajectory model based on the Feynman path-integral formulation. In this framework, ionization process is divided into two steps: (i) an electron tunnels through the potential barrier at an initial time $ t_0 $ and position $ {\boldsymbol{r}}_0 $, and (ii) it propagates classically in the combined laser and ionic fields according to Newton’s equations. Crucially, each trajectory is endowed with a quantum phase accumulated along its path, $ \varPhi_k $, allowing for the coherent summation of all trajectories ending with the same final momentum, $ M_j = \displaystyle\sum\nolimits_k {\mathrm{e}}^{{\mathrm{i}}\varPhi_k} $. Our model combines two critical physical effects beyond standard treatments:• Non-Adiabatic Tunneling: We introduce a non-zero initial longitudinal momentum, $ v_{0 //} =-A(t_0)\times $$ \left(\sqrt{1+\gamma_{\text{eff}}^2}-1\right) $, acquired by the electron at the tunnel exit. This term accounts for the non-instantaneous nature of the tunneling process, a key non-adiabatic effect.• Core Polarization: We include an induced dipole potential, $ U_{\text{ID}} = -\alpha^{\mathrm{I}} {\boldsymbol{E}}(t) \cdot {\boldsymbol{r}}/r^3 $, to model the dynamic polarization of the Ar+ ionic core, a multi-electron effect.By selectively including or excluding these effects, we can clearly isolate their respective contributions to the final PMD. Results: Our central finding is that the non-adiabatic initial longitudinal momentum is the decisive factor for correctly describing the near-threshold interference. The benchmark TDSE calculation for a single intensity of $ 5 \times 10^{13} $ W/cm2 ($ \gamma \approx 1.6 $) reveals a distinct 6-lobe interference pattern. A traditional semiclassical simulation based on the quasi-static tunneling approximation (i.e., setting $ v_{0//} = 0 $) qualitatively fails, predicting an incorrect 8-lobe structure. However, upon including the non-zero initial longitudinal momentum ($ v_{0//} \neq 0 $), our non-adiabatic semiclassical model quantitatively reproduces the correct 6-lobe structure, showing that it is in excellent agreement with the TDSE benchmark.To understand the underlying physics, we perform a quantum-orbit decomposition. This analysis reveals that the overall fan-like structure arises from the interference of multiple trajectory types, including “direct” (Category Ⅰ), “forward-scattered” (Category Ⅱ, and “glory-scattered” (Category Ⅲ) orbits. Although the entire structure arises from the collective interference of these paths, we pinpoint the origin of the lobe-count correction. The initial longitudinal momentum contributes a phase term, $ \Delta\varPhi_{\text{initial}} \approx -{\boldsymbol{v}}_{0//} \cdot {\boldsymbol{r}}_0 $, to the total accumulated action. We find that the relative phase between the “direct” and “glory” trajectories is exquisitely sensitive to this term due to their vastly different paths and birth conditions. It is this specific and dramatic change in the Ⅰ-Ⅲ interference channel that ultimately corrects the topology of the entire pattern, reducing the lobe count from 8 to 6. In contrast, other interference pairs, such as the holographic pair Ⅱ-Ⅲ, are largely robust against this effect as their nearly identical birth conditions cause the initial phase term to cancel out in their relative phase. In parallel, our simulations show that the ionic core polarization has a negligible effect on this low-energy structure, but is essential for accurately describing higher-energy rescattering features by smoothing unphysical caustics caused by a pure Coulomb potential. Conclusion: We demonstrate clearly that the near-threshold fan-like interference pattern in the multiphoton regime is a direct manifestation of non-adiabatic dynamics during tunneling, specifically the acquisition of a longitudinal momentum component by the electron during its finite-time passage under the potential barrier. Our findings not only provide a clear, intuitive, and orbit-based physical picture for this complex quantum phenomenon but also highlight the predictive power of semiclassical methods when crucial non-adiabatic effects are properly incorporated. This understanding lays a foundation for future investigations, including the extension of this model to more complex molecular systems and its application in retrieving attosecond electron dynamics from holographic interference patterns.

EDITOR'S SUGGESTION

Two-dimensional reconstruction method of combustion field temperature and gas concentration based on adaptive region weight mixing model
CHEN Chuge, SHI Dingfeng, CONG Zhouyang, HUANG An, XU Zhenyu, NIE Wei, XIA Huihui, GUO Haofan
2025, 74 (21): 214203. doi: 10.7498/aps.74.20250988
Abstract +
Diagnosis of combustion flow fields in aeroengines, scramjets, and related systems plays a crucial role in understanding combustion mechanisms, evaluating combustion stability and performance, and and is also a major challenge in the development of advanced propulsion technologies. Among the non-intrusive diagnostic approaches, laser absorption spectroscopy has become one of the most representative techniques. In particular, tunable diode laser absorption spectroscopy (TDLAS) offers advantages such as a compact system architecture, easy miniaturization, strong environmental adaptability, and the capability of simultaneous temperature and concentration measurements. By employing multiple laser beams intersecting at different angles and collecting absorption spectra along various paths, the two-dimensional distribution of flow-field parameters can be reconstructed using computed tomography (CT) algorithms.However, traditional nonlinear tomographic algorithms based on polynomial models encounter difficulties in reconstructing flow fields with steep gradients. To solve this problem, we propose a hybrid reconstruction method that integrates a regional weighting mechanism. In this framework, the polynomial model is combined with a Gaussian radial basis function (RBF) model, and a regional weight matrix is iteratively updated in an adaptive manner. The regional weight matrix is determined by introducing perturbations into the current temperature field and jointly considering its temperature gradient. This design allows the hybrid model to capture global features while enhancing its ability to resolve local details. In addition, a regional weight regularization term is incorporated into the residual function to further improve reconstruction accuracy.To validate the proposed approach, numerical simulations are conducted on three representative combustion field distributions, and comparisons are made between polynomial model, RBF model, and traditional algebraic reconstruction technique (ART) algorithms. The results demonstrate that the hybrid model achieves higher representational capability and reconstruction accuracy, with maximum temperature and concentration errors reduced to 3.31% and 7.13% (for the Top-Hat case), respectively. A scanning TDLAS measurement platform and a thermocouple measurement platform are built on a standard McKenna burner to experimentally verify the method. The reconstructed distribution has good consistency with the experimental results, and the deviation between the reconstructed 1800 K central temperature and the thermocouple measurement value is only 10 K. These findings verify the effectiveness of the proposed method and highlight its potential as a reliable tool for combustion field diagnostics in propulsion systems.

EDITOR'S SUGGESTION

Study on risk of triboelectric charging and discharging of lunar rovers in lunar surface environment
XIA Qing, LI Mengyao, CAI Minghui, TANG Chengxiong, ZHANG Zun, YANG Tao, XU Liangliang, JIA Xinyu
2025, 74 (21): 219401. doi: 10.7498/aps.74.20251035
Abstract +
With China’s lunar exploration program steadily advancing from the landmark orbiting missions of Chang’e-1 to the historic sample-return feats of Chang’e-5 and the groundbreaking far-side landing of Chang’e-4, China has entered a critical phase of deepening lunar exploration, including preparations for crewed lunar missions. Among these ambitious endeavors, identifying and mitigating potential operational risks is crucial to ensuring the success of these ambitious efforts. This work focuses on a critical hazard unique to China’s lunar surface exploration efforts: the triboelectric charging and discharging phenomenon between lunar rover wheels and lunar dust, which has a significant impact on astronaut safety and the reliability of onboard electronic systems.Lunar surface missions will face the risk of triboelectric charging and discharging resulting from friction between lunar rover wheels and lunar dust. Preliminary theoretical studies indicate that metal wheels may become charged to a level of approximately –5000 V, with discharge pulse currents reaching an order of magnitude of 0.1 A, posing a severe threat to astronaut safety and the normal operation of device circuits.This paper employs ground-based experimental methods to investigate the triboelectric charging and discharging risks of lunar rover wheels in vacuum and simulated solar wind plasma environments. The research findings are given below.In a vacuum environment, when an aluminum alloy lunar rover wheel (136 mm in diameter) travels on a lunar dust layer at a speed of 0.003 m/s, it rapidly charges to a positive potential of several hundred volts. Discharge breakdown occurs when the wheel travels approximately 20 m and reaches a potential of 550 V. At this point, the captured discharge current pulse amplitude can reach 1.5 A, with a pulse duration of about 100 ns. Increasing the friction frequency significantly accelerates the charging rate and leads to more frequent discharges.In a simulated solar wind plasma environment, when the wheel travels at 0.003 m/s, the combined effect of the environment and friction results in a negative charging potential. After reaching equilibrium, the potential stabilizes at approximately –830 V, and discharges occur more frequently than in a vacuum environment. Discharge breakdown takes place when the wheel travels just 8.5 m, with the discharge current pulse amplitude reaching up to 0.3 A and a pulse duration of 100 ns.These discharge pulses cause electromagnetic interference to linear circuits, leading to abnormal output of voltage signals in subsequent modes. The abnormal signals have an amplitude on the order of 10 V and a duration of 29 ms.This study confirms that the risk of triboelectric charging and discharging in lunar rovers is relatively high. Although theoretical models predict that the lunar roving vehicle (LRV) would experience rapid dissipation of triboelectric charges (with no charging/discharging risk) when operating at 0.03 m/s, the experiments show that even at a slow speed of 0.003 m/s, the wheels still accumulate charges and experience frequent discharge breakdowns. The amplitude of discharge pulse can reach the level of 1 ampere, causing significant electromagnetic interference to nearby circuits. Clearly, theoretical models underestimate the risk of triboelectric charging and discharging in lunar surface environments. It is recommended that future engineering tasks pay close attention to this issue and further evaluate the extent of its hazards.

EDITOR'S SUGGESTION

Distributions of asymptotic transformation rates among quantum states
GAO Dongmei
2025, 74 (21): 210301. doi: 10.7498/aps.74.20250877
Abstract +
In quantum resource theories, manipulating and transforming resource states are often challenging due to the presence of noise. The resource manipulation process from a high resource state $ {\boldsymbol \rho} $ to a low resource state $ {\boldsymbol \rho} ' $ involves asymptotic multiple state replicas, which can be considered as overcoming this problem. Here, the asymptomatic transformation rate $ R\left( {{\boldsymbol \rho} \to {\boldsymbol \rho} '} \right) $ can characterize the corresponding quantum manipulation power, and can be calculated as the ratio of the copy number of initial states to the copy number of target states. Generally, the precise computations of asymptotic transformation rates are challenging, so it is important to establish rigorous and computable boundaries for them. Recently, Ganardi et al. have shown that the transformation rate to any pure state is superadditive for the distillable entanglement. However, it remains a question whether the transformation rate to any noise state is also superadditive in the general resource theory. Firstly, we study the general superadditive inequality satisfied by the transformation rate $ R\left( {{\boldsymbol \rho} \to {\boldsymbol \rho} '} \right) $ of any noise state $ {\boldsymbol \rho} ' $. In any multiple quantum resource theory, we also show that the bipartite asymptomatic transformation rate obeys a distributed relationship: when $ \alpha \geqslant 1 $, $ {R^\alpha }\left( {{\boldsymbol \rho} \to {\boldsymbol \rho} '} \right) $ satisfies monogamy relationship. Using similar methods, we demonstrate that both the marginal asymptotic transformation rate and marginal catalytic transformation rate satisfies these relationships. As a byproduct, we show an equivalence among the asymptomatic transformation rate, marginal asymptotic transformations, and marginal catalytic transformations under some restrictions. Here marginal asymptotic transformations and marginal catalytic transformations are special asymptotic transformations, where the initial state can be reduced into target state at a nonzero rate. These inequality relationships impose a new constraint on the quantum resource distribution and trade off among subsystems. Recently, reversible quantum resource manipulations have been studied, and it is conjectured that transformations can be reversibly executed in an asymptotic regime. In the future, we will explore a conclusive proof of this conjecture and then study the distributions of these reversible manipulations.

EDITOR'S SUGGESTION

Dissociation of fluoromethane trication induced by highly charged ion collisions
TAN Xu, FANG Fan, ZHANG Yu, SUN Dehao, WU Yijiao, YIN Hao, MENG Tianming, TU Bingsheng, WEI Baoren
2025, 74 (21): 213401. doi: 10.7498/aps.74.20251099
Abstract +
Investigating molecular fragmentation mechanisms and the kinetic energy distributions of fragments can offer crucial insights into their roles in plasma physics, radiation-induced damage in biological tissues, and interstellar chemistry. In this study, we conduct the experiments on collision between 3 keV/u ${\rm Ar}^{8+} $ ions and CH3F molecules by using a cold target recoil ion momentum spectrometer (COLTRIMS).We focus on the three-body fragmentation channel H++$ {\mathrm{C}\mathrm{H}}_{2}^{+} $+F+ resulting from C—F and C—H bond cleavage in CH3F3+ ions, and measure the three-dimensional momentum vectors of all fragment ions. The fragmentation mechanism involved is analyzed using ion-ion kinetic energy correlation spectra, Newton diagrams, Dalitz plots, and other correlation spectra.Our results reveal two different dissociation mechanisms for the H++$ {\mathrm{C}\mathrm{H}}_{2}^{+} $+F+ channel, i.e. concerted fragmentation and sequential fragmentation, with the former one being dominant. In the sequential fragmentation process, H+ and the intermediate CH2F2+ are firstly formed, followed by further fragmentation of the intermediates into $ {\mathrm{C}\mathrm{H}}_{2}^{+} $ and F+. No sequential pathways involving HF2+ or $ {\mathrm{C}\mathrm{H}}_{3}^{2+} $ intermediates are identified. Furthermore, we observe two types of concerted fragmentation processes with different dynamical characteristics, suggesting that hydrogen atoms in CH3F3+ may occupy different chemical environments. This phenomenon can originate from either molecular isomerization producing different structural geometries or the Jahn-Teller effect leading to inequivalent C—H bonds. This study reveals the three-body dissociation dynamics of CH3F3+ induced by highly charged ion collisions, highlighting the significant role of the Jahn-Teller effect or molecular isomerization in the ionic dissociation of polyatomic molecules.

EDITOR'S SUGGESTION

Investigation of self-bleaching wavelength of Yb-doped fiber lasers
TAO Mengmeng, WANG Yamin, WANG Ke, CHEN Hongwei, SHAO Chongyun, LI Qiaomu, YE Jingfeng
2025, 74 (21): 214205. doi: 10.7498/aps.74.20251017
Abstract +
In radiation environments, the radiation induced attenuation (RIA) of the active optical fiber can lead to a significant decline in the performance of fiber laser system. An effective way to solve this problem is to bleach the active fiber using pumps at certain wavelengths, namely photo-bleaching. Experiments have shown that output power of irradiated Yb-doped fiber laser experiences remarkable recovery under 976-nm pump. However, under 976-nm pump, signals at both 976 nm and 1070 nm co-exist in Yb-doped fiber. Moreover, it is difficult to distinguish which wavelength is responsible for the photo-bleaching process. Herein, a one-hundred-watt level Yb-doped fiber laser is irradiated with gamma-ray radiation. In the radiation process, a significant output decline from 129 W at 0 Gy to 81 W at 100 Gy is observed. Then, self-bleaching test is conducted with 976-nm pump. After 2-h bleaching, the output power is restored to 111 W, corresponding to a recovery ratio of about 37.0%. To verify the specific wavelength responsible for the performance recovery, photo-bleaching characteristics of Yb-doped fiber lasers are investigated under different pump wavelengths including 915, 976, 1070 and 1550 nm. Experiments show that laser signal at 1 μm waveband is the primary cause for the bleaching of Yb-doped fibers, while, the pump at 915, 976 and 1550 nm can hardly bleach the irradiated Yb-doped fiber. The RIA recovery curves of Yb-doped fibers are measured under different 1070-nm bleaching powers. And, related evolution parameters are obtained through curve fitting. With these parameters, the RIA evolution of the Yb-doped fiber and the corresponding output power evolution of the Yb-doped fiber laser in the radiation and bleaching process are simulated. Comparisons show that the numerical results are consistent with the measurements qualitatively, demonstrating the reliability of the model. This work has guiding significance for predicting the performance of fiber laser systems in radiation and bleaching environments.

EDITOR'S SUGGESTION

High-precision calculation of dynamic electric dipole polarizability of $^{11}\mathrm{Be}^{2+}$ ion
WU Fangfei, SHI Haotian, QI Xiaoqiu, ZUO Yani
2025, 74 (21): 213101. doi: 10.7498/aps.74.20250972
Abstract +
11Be, as a typical one-neutron halo nucleus, is of unique significance in studying atomic and nuclear physics. The nucleus comprises a tightly bound 10Be core and a loosely bound valence neutron, forming an exotic nuclear configuration that is significantly different from traditional nuclear configuration in both magnetic and charge radii, thereby establishing a unique platform for investigating nuclear-electron interactions. In this study, we focus on the helium-like 11Be2+ ion and systematically calculate the energies and wavefunctions of the $n^{3}S_1$ and $n^{3}{\mathrm{P}}_{0,1,2}$ states up to principal quantum number $n=8$ by employing the relativistic configuration interaction (RCI) method combined with high-order B-spline basis functions. By directly incorporating the nuclear mass shift operator $H_{\mathrm{M}}$ into the Dirac-Coulomb-Breit (DCB) Hamiltonian, we comprehensively investigate the relativistic effects, Breit interactions, and nuclear mass corrections for 11Be2+. The results demonstrate that the energies of states with $n\leqslant 5$ converge to eight significant digits, showing excellent agreement with existing NRQED values, such as $-9.29871191(5)$ a.u. for the $^{3}{\mathrm{S}}_1$ state. The nuclear mass corrections are on the order of 10–4 a.u. and decrease with principal quantum number increasing.By using the high-precision wavefunctions, the electric dipole oscillator strengths for $k^3{\mathrm{S}}_1 \rightarrow m^3{\mathrm{P}}_{0,1,2}$ transitions ($k \leqslant 5$, $m \leqslant 8$) are determined, resulting in low-lying excited states ($m\leqslant4$) accurate to six significant digits, thereby providing reliable data for evaluating transition probabilities and radiative lifetimes. Furthermore, the dynamic electric dipole polarizabilities of the $n'^3{\mathrm{S}}_1$ ($n' \leqslant 5$) states are calculated using the sum-over-states method. The static polarizabilities exhibit a significant increase with principal quantum number increasing. For the $J=1$ state, the difference in polarizability between the magnetic sublevels $M_J=0$ and $M_J=\pm1$ is three times the tensor polarizability. In the calculation of dynamic polarizabilities, the precision reaches 10–6 in non-resonant regions, whereas achieving the same accuracy near resonance requires higher energy precision. These high-precision computational results provide crucial theoretical foundations and key input parameters for evaluating Stark shifts in high-precision measurements, simulating light-matter interactions, and investigating single-neutron halo nuclear structures.
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