Accepted Papers
Recent catalogue
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Vol.74 No.20
2025-10-20
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Vol.74 No.19
2025-10-05
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Vol.74 No.18
2025-09-20
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Vol.74 No.17
2025-09-05
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VIEWS AND PERSPECTIVES
2025, 74 (20): 200201.
doi: 10.7498/aps.74.20250864
Abstract +
The multilayer structure of extreme ultraviolet (EUV) masks limits the penetration depth of traditional inspection techniques at non-working wavelengths, thus hindering the effective examination of buried phase defects. Developing defect characterization techniques operating at the 13.5 nm wavelength is crucial for overcoming the quality bottleneck in EUV mask fabrication. Synchrotron radiation light source, with their stable EUV wavelength, cleanliness, and high power density, represents an ideal light source for EUV mask defect characterization research. In this work the current state of technology development for mask characterization at the world's four major synchrotron radiation facilities are systematically reviewed. Through comparative analysis, their working principles, technical advantages, and limitations are investigated in depth, and provide a forward-looking discussion on future trends. In response to the specific requirements for EUV mask defect detection and review, this paper discusses the requirements for the next-generation system platform, which integrates deep detection and review functions, develops novel compact light sources, and innovatively combines the advantages of various imaging techniques to improve the numerical aperture (NA) of imaging systems. This aims to achieve a theoretical resolution of over 20 nm, meeting the future demands of the EUV lithography industry for higher NA (>0.55) and shorter wavelengths (6.7 nm). Regarding the prospects of extending synchrotron radiation to industrial applications, a compact synchrotron radiation source, which can be developed on-site in semiconductor facilities, is introduced to accelerate the research and development cycle, while achieving the synergistic integration of imaging technologies. This paper focuses on the application of phase recovery principle of ptychography to Fourier synthesis illumination (FSI), achieving aberration correction in lens-based systems through synthetic aperture extension. In this paper, the working principles, performance benchmarks, technical challenges, and emerging development trends of existing synchrotron radiation-based EUV mask characterization techniques are investigated. It provides an important reference for designing next-generation EUV mask characterization system platforms.
GENERAL
2025, 74 (20): 200202.
doi: 10.7498/aps.74.20250982
Abstract +
Clouds exert a significant influence on infrared radiation, making cloud detection a crucial step in the application of infrared hyperspectral data. In particular, water vapor interference and the limited accuracy in high-cloud identification constitute two key challenges for ground-based infrared hyperspectral cloud detection. Traditional threshold-based cloud detection methods are difficult to adapt to different locations and dynamically changing atmospheric conditions,while machine learning methods can achieve cloud detection with higher accuracy, greater robustness, and improved automation. Building on the advantages of machine learning, observational data from the atmospheric sounder spectrometer by infrared spectral technology (ASSIST), collected at Lijiang (Yunnan), Motuo (Xizang Autonomous Region), and Ritu (Xizang Autonomous Region) in China, are used to analyze the spectral differences between sunny and cloudy conditions in this study. Based on these differences, a spectral feature enhancement-driven machine learning method for cloud detection is proposed. Finally, by incorporating synchronous observations from lidar, meteorological stations, and all-sky imagers, the proposed method is systematically evaluated under different relative humidity (RH) and cloud base height (CBH) conditions. The experimental results show that the consistency between the results obtained by the proposed method and lidar-based detection is as high as 97.61%. Under different RH conditions, the proposed method outperforms the method based on original spectral features. Notably, when ${\text{RH}} > 70{\text{%}} $, the accuracy of clear-sky spectral identification improves significantly: increasing from 86.01% to 91.89%. Similarly, under different CBH conditions, the proposed method also exhibits superior performance compared with the method in which original spectral features are used. In particular, the accuracy improvements are especially notable when identifying mid-level clouds with ${\text{3 km}} < {\text{CBH}} \leqslant 5{\text{ km}}$, as well as high-level clouds with ${\text{CBH}} > 5{\text{ km}}$. When ${\text{3 km}} < {\text{CBH}} \leqslant 5{\text{ km}}$, the accuracy increases from 95.45% to 98.64% and when ${\text{CBH}} > 5{\text{ km}}$, the accuracy improves from 87.5% to 91.67%. The proposed method significantly enhances the automation and accuracy of cloud detection, thereby providing higher-quality fundamental datasets for supporting subsequent applications such as radiative transfer simulation, remote sensing parameter retrieval, and data assimilation in numerical weather prediction (NWP) models.
GENERAL
2025, 74 (20): 200301.
doi: 10.7498/aps.74.20250715
Abstract +
Entanglement detection and classification of different kinds of entangled states in quantum many-body systems have always been a key topic in quantum information and quantum computation. In this work, we investigate the entanglement detection and classification of three special entangled states: 4-qubit GHZ state, 4-qubit $ {\mathrm{W}}\overline{{\mathrm{W}}} $ state, and 4-qubit SGT state, which cannot be distinguished by the general quantum Fisher information (QFI) under the usual local operations. By utilizing the experimentally mature and controllable one-axis twisting model, along with optimized rotations and adjustable interaction strength, we successfully classify the three states by QFI. Additionally, we also study the effects of four types of environmental noise on entanglement detection, namely, bit-flip channel, amplitude-damping channel, phase-damping channel, and depolarizing channel. The results show that under local operations, the changes of the QFI from the 4-qubit GHZ state with decoherence parameter p in four noise channels are significantly different from those of the $ {\mathrm{W}}\overline{{\mathrm{W}}} $ state and SGT state, and thus making them distinguished. However, the QFI about the $ {\mathrm{W}}\overline{{\mathrm{W}}} $ state and the QFI about the SGT state exhibit the same variations and cannot be classified. In the one-axis twisting model, the variation curves of the QFI of the three states under the four noise channels are different from each other, which can be clearly observed. It should be noted that in the bit-flip channel, the QFI curves of the $ {\mathrm{W}}\overline{{\mathrm{W}}} $ state and the SGT state overlaps in the middle region ($ p\approx0.5 $), which prevents their classification. Our work provides a new method for entanglement detection and classification in quantum many-body systems, which will contribute to future research in quantum science and technology.
INSTRMENTATION AND MEASURMENT
2025, 74 (20): 200401.
doi: 10.7498/aps.74.20250852
Abstract +
Gravitational wave astronomy has rapidly developed into a powerful means of probing compact objects and understanding the evolution of the Universe. In order to improve sensitivity and expand the detection band, ground-based laser interferometers such as LIGO, Virgo, and KAGRA are constantly upgraded. This review summarizes their systematic development with an emphasis on noise sources and mitigation strategies. After outlining the principle of gravitational wave detection with laser interferometry, we analyze dominant noise sources, including quantum vacuum fluctuations, thermal noise, and seismic disturbances, and introduce techniques such as frequency-dependent squeezed light, advanced seismic isolation, multi-stage suspensions, and cryogenic mirrors. For LIGO, we highlight the transition from the Initial to Advanced configurations, which results in strain sensitivities of the order of $10^{-24}/\sqrt{\text{Hz}}$ and leads directly to the first detection, GW150914, and over one hundred subsequent events during O1 to O4. The unique superattenuator system of Virgo and its recent implementation of squeezed light, as well as the underground design of KAGRA and the use of cryogenic sapphire test masses, represent different approaches to suppressing low-frequency and thermal noise. In addition, we compare the technical routes adopted by different detectors and summarize the lessons learned from their upgrades, thereby providing valuable guidance for designing future detectors. Finally, we present next-generation projects, including LIGO Voyager, the Cosmic Explorer, and the Einstein Telescope, which aim to increase sensitivity by up to orders of magnitude and provide new research opportunities for developing gravitational-wave cosmology and fundamental physics. Overall, the development of detector technologies has been a key driving force for advances in gravitational wave astronomy, and the forthcoming facilities will change our ability to explore the universe.
GENERAL
2025, 74 (20): 200501.
doi: 10.7498/aps.74.20250954
Abstract +
The rich dynamical analysis and predefined-time synchronization of simple memristive chaotic systems are of great significance in fully understanding the mechanism of dynamics formation and expanding the potential applications of chaotic systems. A four-dimensional memristive chaotic system with only a single nonlinear term is proposed to reveal various dynamic behaviors under the change of parameters and initial conditions, and to realize effective synchronization control. Based on dissipativity analysis and Lyapunov exponent computation, and combined with bifurcation analysis and multi steady state exploration, it is shown that the system possesses an infinite number of unstable equilibrium points and exhibits homogeneous and heterogeneous multistability, including point attractors, periodic attractors, and chaotic attractors. Moreover, it is found that amplitude modulation of the output signals of the system can be precisely achieved by adjusting internal parameters of the memristor, thus providing a theoretical basis for achieving effective amplitude modulation of periodic and chaotic signals. A predefined-time sliding mode surface with linear and bidirectional power-law nonlinear decay terms is constructed to address synchronization. Sufficient conditions for predefined-time convergence of synchronization errors are derived using Lyapunov stability theory, and a double-stage sliding mode controller with an adjustable upper bound on synchronization time is designed. The resulting control law ensures an adjustable synchronization time bound and rapid error suppression under arbitrary disturbances. Numerical simulations further confirm the effectiveness and robustness of the proposed control scheme, indicating that even under external disturbances or significant variations in initial conditions, the error variables can still converge precisely within the predefined time.
GENERAL
2025, 74 (20): 200601.
doi: 10.7498/aps.74.20251032
Abstract +
The measurement of total energy on a target is a critical step in evaluating the performances of high-power laser systems. However, the laser spot on the target exhibits characteristics such as high power density, non-uniform spatial distribution and temporal distribution, and large spot size, which present a significant challenge to the accurate measurement of total energy. To meet the requirement for high-precision measurement of the total energy of a large spot, this work focuses on plate-based energy measurement technology. First, we investigate the physical processes of laser-heated plates and obtain analytical solutions, demonstrating that uniformly arranged temperature sensor arrays can shorten the relaxation period. Second, to overcome the limitations of traditional energy inversion algorithms, such as the need to preheat the absorber and potential non-uniform temperature effects, we propose correction methods. The non-preheated calorimetry method eliminates the requirement that the absorber temperature must be higher than the ambient temperature during the initial rating period. It iteratively optimizes the ambient temperature and heat loss coefficients based on corrected temperature invariance. Additionally, a non-uniform temperature correction algorithm is employed to minimize the errors caused by limited sensor sampling rates through reconstructing the temperature curve during the injection and adjustment periods. Finally, we develop a plate measurement device and conduct laser calibration tests, achieving a system repeatability of 2.7%, linearity of 0.3%, and a combined standard uncertainty of 4%. This study lays a theoretical foundation for flat-plate laser energy measurement technology, offering important insights into optimizing the apparatus design, improving usability, and achieving high-precision energy inversion.
GENERAL
2025, 74 (20): 200602.
doi: 10.7498/aps.74.20250915
Abstract +
Torsion information is important for rotating systems, industrial monitoring, transportation engineering, and medical equipment. Optical fiber torsion sensors have significant advantages, such as immune to electromagnetic interference, small size, and light weight. Sagnac loop interferometer (SI) torsion sensors have attracted much attention due to their compact structure, high sensitivity, excellent stability, and low cost. However, their nonlinear response limits the measurement range, while the wide full width at half maximum and low signal-to-noise ratio (SNR) reduce the resolution of torsion sensors. To solve these problems, a fiber ring laser torsion sensor (FRLTS) based on homemade polarization-maintaining photonic crystal fiber (PM-PCF) is proposed in this work. The torsion sensor introduces a PM-PCF based SI into the erbium-doped fiber ring cavity as a filter and torsion sensor device. The interference spectrum of SI is derived by the transmission matrix method and simulated, and then the sensing principle of the sensor is obtained. Subsequently, the experimental system is set up to study the lasing output characteristics and torsion response of the FRLTS. By taking advantage of the narrow linewidth and high signal-to-noise ratio (SNR) of fiber ring lasers, a high-resolution fiber torsion sensor is successfully obtained. The experimental results show that the maximum linear torsion measurement range of the sensor can be extended to 480° (from –260° to 220°), the maximum torsion sensitivity is 0.032 nm/(°), and the resolution is as high as 0.681°. Furthermore, in a temperature range from 20 ℃ to 95 ℃, the temperature-induced wavelength variation is only 4×10–3 nm/℃, corresponding to a torsion angle measurement error of 0.16(°)/℃. Compared with existing reports, its temperature stability is increased by 37.5 times, while the temperature-induced error in angle measurements is reduced by 9.375 times. The proposed FRLTS not only successfully achieves high-resolution and wide-range torsion sensing, but also effectively suppresses cross-sensitivity caused by temperature. Therefore, the torsion sensor has significant potential applications in fields such as aerospace and robotics where precise measurement of minute torsion angle is required in special environments.
SPECIAL TOPIC—High-pressure modulation and in situ characterization of optoelectronic properties
2025, 74 (20): 200701.
doi: 10.7498/aps.74.20251034
Abstract +
Two-dimensional (2D) materials, due to their outstanding photoelectric properties, have demonstrated significant potential in both fundamental scientific research and future technological applications, including optoelectronics, energy storage, and conversion devices, establishing them as a cutting-edge research field in condensed matter physics and materials science. The distinctive layered structure of 2D materials renders their physical properties highly sensitive to external stimuli. High-pressure technology, serving as an efficient, continuous, and clean tuning tool, enables precise structural control and optimization of the photoelectric properties of 2D materials by compressing atomic distances, strengthening interlayer coupling, and even inducing structural phase transitions. This article focuses on prototypical two-dimensional materials, including graphene, transition metal dichalcogenides (TMDs), and two-dimensional metal halide perovskites. Employing the diamond anvil cell combined with multimodal in situ high-pressure characterization techniques such as X-ray diffraction, Raman spectroscopy, photoluminescence, and electrical transport measurements, we systematically elucidate the effects of high pressure on the structural and photoelectric properties of these materials. The key findings indicate that high pressure can induce the graphene to transition from a semimetal state to a semiconducting state, even a superconducting state, triggering off structural phase transitions and semiconductor-to-metal transitions in TMDs such as MoS2 and WTe2, and leading to a pressure-dependent bandgap narrowing and significant enhancement of luminescence intensity in two-dimensional perovskites. This work highlights the utility of high-pressure techniques in revealing the intrinsic correlations between the microstructure and macroscopic properties of two-dimensional materials. Furthermore, it discusses the key challenges and opportunities in this emerging research area, providing insights into the development and practical application of novel functional materials.
GENERAL
2025, 74 (20): 200702.
doi: 10.7498/aps.74.20250824
Abstract +
Coherence, as a core element of cutting-edge X-ray research technology, has driven the vigorous development of many experiments such as coherent X-ray diffraction imaging and X-ray holography in the past two decades, as well as the construction of fourth-generation synchrotron radiation sources and hard X-ray free electron lasers. To measure the size of synchrotron radiation light source and coherence of beamline, an X-ray measurement system based on two-dimensional (2D) single grating interferometry is established in this work, and the measurement principles and propagation models used in the system are also investigated. Firstly, based on the VanCittert-Zernike theorem, the relationship between the visibility of the interference lattice and the spatial coherence of X-rays is established. Secondly, by combining the Talbot self imaging effect of a single grating, the X-ray spatial coherence length of the grating plane is measured, and the spatial distribution of the corresponding light source is obtained through further calculation. The relevant measurement experiments of this study are conducted at the BL09B bending magnet beamline of the Shanghai Synchrotron Radiation Facility (SSRF). A 2D checkerboard π phase-shift grating is used as the core device in the experiment. This setup can not only enable the acquisition of transverse coherence lengths in the vertical and horizontal directions but also further measure the transverse coherence lengths in the directions forming 45° and 135° angles with respect to the horizontal direction. The experimental process strictly follows the technical specifications outlined in this paper: measuring interferograms at different positions downstream of the phase grating along the beam propagation direction. For each interferogram, the corresponding visibility values are extracted by analyzing the harmonic peaks in its Fourier-transformed image. Ultimately, the transverse coherence length in each direction is derived based on the evolution law of visibility as a function of the grating-to-detector distance. The experimental results show that the coherence length of the emitted X-rays on SSRF testline is 4.2 μm(H)×13.8 μm(V) at 15 keV, and the size of the bending magnet source is 124 μm(H)×38 μm(V). The results obtained by this method can provide important references for measuring the electron source size and developing experimental methods with high requirements for uniform illumination.
NUCLEAR PHYSICS
2025, 74 (20): 202101.
doi: 10.7498/aps.74.20250898
Abstract +
In this work, we investigate the properties of strange quark matter (SQM) and color-flavor-locked (CFL) quark matter under zero temperature or strong magnetic fields within MIT bag model. We find that the thermodynamical properties of CFL quark matter are strongly affected by pairing energy gap Δ and magnetic field. The sound velocity of CFL quark matter and the tidal deformability of CFL quark stars both increase with Δ increasing, while the central baryon density of the maximum star mass in CFL state decreases with Δ. Specifically, the equation of state (EOS) of the CFL quark matter becomes stiffer with the increase of Δ, and the pressure becomes anisotropic when considering the magnetic field in the CFL quark matter. Our results indicate that the mass-radius relations of the CFL quark matter within the MIT bag model can describe the recent observations of pulsars, and that the maximum mass of CFL quark star increases with the increase of Δ. Moreover, the research results indicate that the mass of CFL quark star depends on the magnetic field strength and its orientation distributions within the magnetars, and the polytropic index of CFL quark matter decreases with the increase of star mass.
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