Accepted
, , Received Date: 2025-09-01
Abstract +
The virtual cathode is an important phenomenon in thermionic emission, and it is widely present in various electronic devices and systems such as vacuum tubes, electron guns, high-power microscopes, X-ray tubes, concentrated solar thermionic converters, and emissive probes. Since the virtual cathode can directly affect the performance of these devices, it is of great significance to study the characteristics of the virtual cathode and conduct experimental measurements on it. In our recent research, a one-dimensional model of thermionic emission was established, and the analytical expressions for the potential barrier and the spatial width of the virtual cathode were derived. With the development of virtual cathode theories, measuring the virtual cathode experimentally has become a reality. In this study, based on our one-dimensional theoretical model, the absolute error theory of the virtual cathode is established, and the contributions of different parameters, such as the hot-cathode temperature, the saturated electron emission current, the electron collection current, Dushman constant, and the work function of hot cathodes, to the absolute errors in the virtual cathode measurement are systematically analyzed. The research results show that the main factors affecting the measurement of the virtual cathode potential are closely related to the size of the virtual cathode. When the virtual cathode potential generated by hot-cathodes is strong, the uncertainty of the hot-cathode temperature becomes the main error source, with a probability of about 61% for the potential barrier measurement, but when the virtual cathode is weak, the main factor becomes the uncertainty of the electron current measurement with a probability of about 39%. Besides, when measuring the virtual cathode width, for common hot-cathodes such as oxide (BaO) cathode, tungsten cathode, and molybdenum cathode, the main factors affecting the measurement results are the uncertainties in the hot-cathode temperature and the work function. These uncertainties account for approximately 94%, 96% and 97% of the measurement variability, corresponding to the above three cathodes, respectively. Only when the virtual cathode is very weak, does the uncertainty of the electron current become the main error source for the measurement of the virtual cathode width.
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Abstract +
Moiré lattices are photonic lattices featuring moiré patterns.Quasiperiodic photonic moiré lattices possess flat energy bands,enabling the localization of the beam and long-distance optical guiding.However,intense lasers alter the induced refractive index of photorefractive crystals,limiting milliwatt-level guiding in quasiperiodic moiré lattices based on such materials.To realize effcient optical guiding with long-distance and low-dispersion propagation,this study introduces the concept of moiré lattices into plasmas,leveraging the high damage threshold of plasmas,and proposes a plasma moiré lattice.
Theoretical calculations were performed by approximating quasiperiodic moiré lattices with periodic ones constructed using specific adjacent angles and employing the finite difference method.It is demonstrated that plasma moiré lattices also exhibit flat energy bands where the propagation constant remains independent of the transverse wavenumber,providing a theoretical foundation for long-distance guiding.
Three-dimensional particle-in-cell simulations were conducted to investigate the guiding characteristics of relativistic intense laser pulses (a0=1,corresponding to Ez =4 × 1012 V/m) in plasma moiré lattices.Under the given parameters,the lattice can effectively confine laser pulses of different initial spot sizes to a similar channel depth,enabling stable long-distance propagation over d=1000λ0.When the initial spot size exceeds the channel depth,part of the beam energy converges toward the center,leading to an increase in the peak intensity by a factor of two,while the other part is scattered,resulting in a decrease in total energy.
Under conditions of matched average density,compared to conventional preformed parabolic plasma density channels,the plasma moiré lattice significantly suppresses laser redshift usually caused by wakefield excitation.For example,for a high-energy short pulse (W=25.4 mJ,τ0=15λ0) or a low-energy long pulse (W=2 mJ,τ0=30λ0),the redshift in the moiré lattice is markedly less than that in the parabolic channel after propagating d=800λ0,as stronger wakefield is excited in the latter.
By scaling the moiré lattice up 75 times,the plasma moiré lattice can effectively guide intense terahertz pulses (center frequency f0=5 THz,λ0=60 µm,a0=0.45,W=24.7 mJ).During long-distance propagation up to 5ZR(Rayleigh length) in the moiré lattice,intense terahertz pulses experience negligible photon deceleration,maintain their original central frequency,and achieve low-dispersion transmission.
The plasma moiré lattice provides a new approach for high-effciency,low-dispersion transmission of intense lasers and terahertz pulses.Potential experimental implementations could involve generating such lattices using two-beam interference with masks or dielectric barrier discharge methods,allowing tunable lattice constants for optimized guiding of diverse electromagnetic pulses.
Theoretical calculations were performed by approximating quasiperiodic moiré lattices with periodic ones constructed using specific adjacent angles and employing the finite difference method.It is demonstrated that plasma moiré lattices also exhibit flat energy bands where the propagation constant remains independent of the transverse wavenumber,providing a theoretical foundation for long-distance guiding.
Three-dimensional particle-in-cell simulations were conducted to investigate the guiding characteristics of relativistic intense laser pulses (a0=1,corresponding to Ez =4 × 1012 V/m) in plasma moiré lattices.Under the given parameters,the lattice can effectively confine laser pulses of different initial spot sizes to a similar channel depth,enabling stable long-distance propagation over d=1000λ0.When the initial spot size exceeds the channel depth,part of the beam energy converges toward the center,leading to an increase in the peak intensity by a factor of two,while the other part is scattered,resulting in a decrease in total energy.
Under conditions of matched average density,compared to conventional preformed parabolic plasma density channels,the plasma moiré lattice significantly suppresses laser redshift usually caused by wakefield excitation.For example,for a high-energy short pulse (W=25.4 mJ,τ0=15λ0) or a low-energy long pulse (W=2 mJ,τ0=30λ0),the redshift in the moiré lattice is markedly less than that in the parabolic channel after propagating d=800λ0,as stronger wakefield is excited in the latter.
By scaling the moiré lattice up 75 times,the plasma moiré lattice can effectively guide intense terahertz pulses (center frequency f0=5 THz,λ0=60 µm,a0=0.45,W=24.7 mJ).During long-distance propagation up to 5ZR(Rayleigh length) in the moiré lattice,intense terahertz pulses experience negligible photon deceleration,maintain their original central frequency,and achieve low-dispersion transmission.
The plasma moiré lattice provides a new approach for high-effciency,low-dispersion transmission of intense lasers and terahertz pulses.Potential experimental implementations could involve generating such lattices using two-beam interference with masks or dielectric barrier discharge methods,allowing tunable lattice constants for optimized guiding of diverse electromagnetic pulses.
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Abstract +
The development of high-performance chip-scale ion traps is pivotal for the integration and scaling of ion-trap-based quantum computers. While cryogenic environments can significantly suppress anomalous heating, operating ion traps at room temperature remains highly attractive for its simplicity and lower cost. This work reports significant progress in coherently controlling multiple ions confined in a custom-fabricated, room-temperature surface-electrode trap, establishing a critical foundation for advanced quantum protocols like quantum error correction and future scalable architectures.
Research Objectives and Methods: Our study aimed to characterize a home-built chip trap and demonstrate its capabilities for multi-ion quantum logic under ambient conditions. The trap features a six-wire electrode design on a high-resistivity silicon substrate, with ions trapped at a height of 154 µm. We employed a combination of Doppler cooling, Electromagnetically Induced Transparency (EIT) cooling, and resolved-sideband cooling to prepare the ions in the motional ground state. Coherent manipulations were performed using both a 729 nm laser (for qubits between the $|\text{S}_{1/2},m_j=-1/2\rangle$ and $|\text{S}_{1/2},m_j=+1/2\rangle$ states) Quantum state detection was achieved via state-dependent fluorescence using an EMCCD camera, enabling site-resolved readout.
Key Results:
Low Room-temperature Heating Rates: The trap exhibited low heating rates, measured to be 0.074(8) quanta/ms in the axial direction (at 833 kHz) and 0.237(51) quanta/ms in the radial direction (at 1.3 MHz). The spectral density of electric-field noise is on the order of 10-13 V2/m2Hz at trap frequencies above 500 kHz, ranking among the best for room-temperature devices. The spectral density of electric-field noise followed an approximate f-2.52(22) dependence, potentially influenced by external filtering circuits.
High-Fidelity Single-Ion Control: A single 40Ca+ ion was cooled to an average phonon number of 0.04(2) in its axial motion. High-fidelity coherent operations were demonstrated: carrier Rabi oscillations using the 729 nm laser showed a single-pulse fidelity of approximately 98.98(8)%, while microwave-driven operations achieved a fidelity of 99.95(2)%. Ramsey interferometry with microwaves revealed a coherence time T*2 of 5.0(4) ms.
Site-Resolved Multi-Ion Coherent Control: The core achievement was the global coherent manipulation of ion chains containing up to 20 ions. We characterized the system by driving motional sideband transitions on various axial modes of 5- and 6-ion chains. The resulting Rabi oscillations, measured with site-resolved fluorescence, clearly showed the collective dynamics and mode-dependent coupling strengths dictated by the normalized mode eigenvectors. Furthermore, global carrier transitions were demonstrated on a 2D zigzag crystal of 20 ions, confirming the ability to execute simultaneous operations on a large qubit array.
Global Control of 2D Ion Crystals: With 20 ions, a 2D zigzag crystal was formed and globally addressed using both laser and microwave drives. Laser-driven carrier transitions showed strong decay due to multimode motional coupling, while microwave-driven oscillations remained nearly decay-free, consistent with the Lamb–Dicke parameter being negligible for microwave fields.
Conclusion: We have successfully demonstrated that our room-temperature surface-electrode trap can support low-heating confinement, high-fidelity single- and multi-qubit operations, and coherent control of large ion arrays. The site-resolved observations of mode-dependent coupling highlight the potential for exploiting collective vibrational modes for selective quantum control. These results validate the trap as a robust and promising platform for medium-scale quantum information processing and quantum simulation at room temperature. Future work will focus on structural optimizations to reduce radial heating and integration with cryogenic systems to further suppress noise, ultimately advancing toward large-scale quantum computing architectures.
Research Objectives and Methods: Our study aimed to characterize a home-built chip trap and demonstrate its capabilities for multi-ion quantum logic under ambient conditions. The trap features a six-wire electrode design on a high-resistivity silicon substrate, with ions trapped at a height of 154 µm. We employed a combination of Doppler cooling, Electromagnetically Induced Transparency (EIT) cooling, and resolved-sideband cooling to prepare the ions in the motional ground state. Coherent manipulations were performed using both a 729 nm laser (for qubits between the $|\text{S}_{1/2},m_j=-1/2\rangle$ and $|\text{S}_{1/2},m_j=+1/2\rangle$ states) Quantum state detection was achieved via state-dependent fluorescence using an EMCCD camera, enabling site-resolved readout.
Key Results:
Low Room-temperature Heating Rates: The trap exhibited low heating rates, measured to be 0.074(8) quanta/ms in the axial direction (at 833 kHz) and 0.237(51) quanta/ms in the radial direction (at 1.3 MHz). The spectral density of electric-field noise is on the order of 10-13 V2/m2Hz at trap frequencies above 500 kHz, ranking among the best for room-temperature devices. The spectral density of electric-field noise followed an approximate f-2.52(22) dependence, potentially influenced by external filtering circuits.
High-Fidelity Single-Ion Control: A single 40Ca+ ion was cooled to an average phonon number of 0.04(2) in its axial motion. High-fidelity coherent operations were demonstrated: carrier Rabi oscillations using the 729 nm laser showed a single-pulse fidelity of approximately 98.98(8)%, while microwave-driven operations achieved a fidelity of 99.95(2)%. Ramsey interferometry with microwaves revealed a coherence time T*2 of 5.0(4) ms.
Site-Resolved Multi-Ion Coherent Control: The core achievement was the global coherent manipulation of ion chains containing up to 20 ions. We characterized the system by driving motional sideband transitions on various axial modes of 5- and 6-ion chains. The resulting Rabi oscillations, measured with site-resolved fluorescence, clearly showed the collective dynamics and mode-dependent coupling strengths dictated by the normalized mode eigenvectors. Furthermore, global carrier transitions were demonstrated on a 2D zigzag crystal of 20 ions, confirming the ability to execute simultaneous operations on a large qubit array.
Global Control of 2D Ion Crystals: With 20 ions, a 2D zigzag crystal was formed and globally addressed using both laser and microwave drives. Laser-driven carrier transitions showed strong decay due to multimode motional coupling, while microwave-driven oscillations remained nearly decay-free, consistent with the Lamb–Dicke parameter being negligible for microwave fields.
Conclusion: We have successfully demonstrated that our room-temperature surface-electrode trap can support low-heating confinement, high-fidelity single- and multi-qubit operations, and coherent control of large ion arrays. The site-resolved observations of mode-dependent coupling highlight the potential for exploiting collective vibrational modes for selective quantum control. These results validate the trap as a robust and promising platform for medium-scale quantum information processing and quantum simulation at room temperature. Future work will focus on structural optimizations to reduce radial heating and integration with cryogenic systems to further suppress noise, ultimately advancing toward large-scale quantum computing architectures.
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Abstract +
As a unique optical phenomenon, the Goos–Hänchen (GH) shift has attracted considerable interest due to its broad potential in high-sensitivity sensing, optical switching, and nanoscale photonic devices. In this work, a multilayer heterostructure constructed by alternating layers of black phosphorene (BP) and silicon (Si) is designed, and its GH shifts are systematically investigated, aiming to achieve large-amplitude, electrically tunable GH shifts in the near-infrared region. Furthermore, we elaborate on the underlying phase-modulation mechanisms and the sensing performance of the proposed structure. Based on the transfer matrix method and the optical conductivity of BP calculated via the Kubo formalism, we comprehensively examine the cooperative effects of polarized modes, structural periodicity, incident optical energy, and external voltage on the evolution of the reflection phase and the consequent GH displacement. The results indicate that the incorporation of BP, through the introduction of complex surface conductivity, substantially modifies the phase response of transverse magnetic (TM) waves near the conventional Brewster angle, converting the original π-phase jump into a continuous and differentiable phase transition. This effect enables a GH shift as large as 40λ even in a single-period structure. Although transverse electric (TE) waves do not exhibit Brewster-angle behavior, several-wavelength-scale GH shifts can still be achieved under near-grazing incidence due to Fabry–Pérot interference. Further analysis reveals that increasing the number of (BP–Si) periods steepens the slope of the reflection phase, thereby enhancing the GH shift of the TM wave from 40λ to 128λ in a fourperiod structure at the incident optical energy of 1.52 eV. In addition, the application of an external voltage modulates the energy bandgap and optical conductivity of BP, providing dual control over the magnitude and angular position of the GH shift. For example, under an external voltage of 0.5 eV, the maximum GH shift of the TM wave in a single-period structure at an incident optical energy of 1.4 eV increases from 184λ to 586λ. The structure also exhibits an ultrahigh refractive index sensitivity exceeding 105λ/RIU toward variations in the refractive index of the terminal medium, with further enhancement under electrical bias. These findings reveal the mechanism through which two-dimensional materials induce phase continuity and enhanced GH shifts, while demonstrating the strong potential of BP–Si multilayers for the development of tunable near-infrared photonic components and high-sensitivity optical sensing platforms.
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Geodesic acoustic modes (GAMs), the high-frequency branch of zonal flows, play a crucial role in regulating turbulence and the associated anomalous transport in tokamaks. Although often treated as electrostatic oscillations, GAMs intrinsically possess an electromagnetic component, manifested as magnetic field perturbations. This component is essential for GAM's interaction with electromagnetic turbulence and for the existence of global GAM eigenmodes. However, a long-standing discrepancy exists between magnetohydrodynamic (MHD) and gyro-kinetic theories regarding the three-dimensional (3D) structure of these perturbations. MHD models consistently predict a full 3D structure, with dominant $m=2$ components in the radial and poloidal magnetic field perturbations and dominant $m=1$ component in the toroidal magnetic field perturbation, where $m$ denotes the poloidal wavenumber. In contrast, most gyro-kinetic studies, adopting the conventional parallel vector potential approximation ($\delta\vec{A} \approx \delta A_\|\vec{b}$), are restricted to describing only the $m=2$ poloidal component while systematically neglecting the radial and parallel (toroidal) components. This limitation has created a theoretical gap, preventing a unified understanding of the electromagnetic nature of GAMs.
To address this issue, we employ a self-consistent electromagnetic gyro-kinetic model without invoking the parallel vector potential approximation. Starting from the linear electromagnetic gyro-kinetic equation, we describe the perturbed distribution functions of both ions and electrons. The model is closed with a self-consistent set of field equations—including the quasi-neutrality condition and both the parallel and perpendicular components of Ampère’s law—which determine the evolution of the electrostatic potential $\delta\phi$, the parallel vector potential $\delta A_\|$, and the parallel magnetic perturbation $\delta B_\|$ (associated with the perpendicular vector potential $\delta A_\perp$). By retaining the full perturbed magnetic vector potential $\delta\vec{A}$, the framework naturally incorporates both parallel current perturbations (linked to $\delta A_\|$) and diamagnetic effects (linked to $\delta B_\|$). Analytical solutions are obtained in the long-wavelength limit for a large-aspect-ratio, circular tokamak, including first-order finite-Larmor-radius (FLR) and finite-orbit-width (FOW) effects.
For the first time within a gyro-kinetic framework, our analysis yields the complete 3D magnetic perturbation structure of the electromagnetic GAM. The results explicitly demonstrate that the radial ($\delta B_r$) and poloidal ($\delta B_\theta$) perturbations exhibit a dominant $m=2$ standing-wave structure, while the parallel perturbation ($\delta B_\|$) exhibits a dominant $m=1$ structure. This spatial structure is in excellent qualitative agreement with the predictions of ideal MHD theory, thereby resolving the long-standing discrepancy between the two theoretical approaches. Moreover, the gyro-kinetic model provides a refined physical picture beyond the reach of single-fluid MHD. The analytical expressions reveal distinct roles of ions and electrons: the $m=2$ radial and poloidal magnetic field perturbations, associated with parallel currents, are more strongly influenced by the ion thermal pressure, whereas the $m=1$ parallel magnetic field perturbation, linked to diamagnetic effects, receives a relatively larger contribution from the electron thermal pressure. These results not only unify the theoretical description of GAM magnetic perturbations but also advance our understanding of their kinetic physics, offering a more accurate foundation for experimental diagnostics and numerical simulation.
To address this issue, we employ a self-consistent electromagnetic gyro-kinetic model without invoking the parallel vector potential approximation. Starting from the linear electromagnetic gyro-kinetic equation, we describe the perturbed distribution functions of both ions and electrons. The model is closed with a self-consistent set of field equations—including the quasi-neutrality condition and both the parallel and perpendicular components of Ampère’s law—which determine the evolution of the electrostatic potential $\delta\phi$, the parallel vector potential $\delta A_\|$, and the parallel magnetic perturbation $\delta B_\|$ (associated with the perpendicular vector potential $\delta A_\perp$). By retaining the full perturbed magnetic vector potential $\delta\vec{A}$, the framework naturally incorporates both parallel current perturbations (linked to $\delta A_\|$) and diamagnetic effects (linked to $\delta B_\|$). Analytical solutions are obtained in the long-wavelength limit for a large-aspect-ratio, circular tokamak, including first-order finite-Larmor-radius (FLR) and finite-orbit-width (FOW) effects.
For the first time within a gyro-kinetic framework, our analysis yields the complete 3D magnetic perturbation structure of the electromagnetic GAM. The results explicitly demonstrate that the radial ($\delta B_r$) and poloidal ($\delta B_\theta$) perturbations exhibit a dominant $m=2$ standing-wave structure, while the parallel perturbation ($\delta B_\|$) exhibits a dominant $m=1$ structure. This spatial structure is in excellent qualitative agreement with the predictions of ideal MHD theory, thereby resolving the long-standing discrepancy between the two theoretical approaches. Moreover, the gyro-kinetic model provides a refined physical picture beyond the reach of single-fluid MHD. The analytical expressions reveal distinct roles of ions and electrons: the $m=2$ radial and poloidal magnetic field perturbations, associated with parallel currents, are more strongly influenced by the ion thermal pressure, whereas the $m=1$ parallel magnetic field perturbation, linked to diamagnetic effects, receives a relatively larger contribution from the electron thermal pressure. These results not only unify the theoretical description of GAM magnetic perturbations but also advance our understanding of their kinetic physics, offering a more accurate foundation for experimental diagnostics and numerical simulation.
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Recent advances in crosstalk simulation using integer-order memristive synapses have shown considerable progress. However, most existing models still employ a single-memristor structure, which constrains synaptic weight modulation and makes it difficult to represent both excitatory and inhibitory synaptic connections in a unified manner. These models also often fail to capture the memory effects and nonlocal dynamic properties inherent in biological neurons. To address these issues, this study introduces a fractional-order memristive bridge synapse model for crosstalk coupling. By combining Hindmarsh–Rose (HR) and FitzHugh–Nagumo (FN) neurons, we construct an 8D heterogeneous coupled neural network based on fractional calculus—designated as the Fractional-Order Memristive Bridge Crosstalk-Coupled Neural Network (FMBCCNN). A major innovation is the incorporation of a fractional-order memristive bridge structure that mimics synaptic connections in a bridge configuration. This design provides both historical memory characteristics and bidirectional synaptic weight regulation, overcoming limitations of traditional coupling forms.
Using dynamical analysis tools such as phase portraits, bifurcation diagrams, and Lyapunov exponents, we systematically investigate how synaptic and crosstalk strengths influence system behavior under conventional fractional-order conditions. The results reveal diverse dynamical behaviors, including attractor coexistence, forward and reverse period-doubling bifurcations, and chaotic crises. Further analysis under the more generalized condition of non-uniform fractional orders shows that, compared with the conventional case, the system maintains continuous periodic motion over broader parameter ranges and exhibits clear parameter hysteresis. Although local dynamic patterns remain similar, the corresponding parameter intervals are substantially widened. In addition, the system displays more concentrated and marked alternation between periodic and chaotic behaviors. We also simulate the effect of varying the fractional-order derivative, offering a more general mathematical characterization of neuronal firing activity.
Finally, the chaotic sequences generated by the system are applied to an image encryption algorithm incorporating bit-plane decomposition and DNA encoding. Security analysis confirms that the encrypted images have pixel correlation coefficients below 0.01 in horizontal, vertical, and diagonal directions, information entropy greater than 7.999, and a key space of 22080. These results verify the excellent encryption performance and reliability of the proposed scheme and the generated sequences.
Using dynamical analysis tools such as phase portraits, bifurcation diagrams, and Lyapunov exponents, we systematically investigate how synaptic and crosstalk strengths influence system behavior under conventional fractional-order conditions. The results reveal diverse dynamical behaviors, including attractor coexistence, forward and reverse period-doubling bifurcations, and chaotic crises. Further analysis under the more generalized condition of non-uniform fractional orders shows that, compared with the conventional case, the system maintains continuous periodic motion over broader parameter ranges and exhibits clear parameter hysteresis. Although local dynamic patterns remain similar, the corresponding parameter intervals are substantially widened. In addition, the system displays more concentrated and marked alternation between periodic and chaotic behaviors. We also simulate the effect of varying the fractional-order derivative, offering a more general mathematical characterization of neuronal firing activity.
Finally, the chaotic sequences generated by the system are applied to an image encryption algorithm incorporating bit-plane decomposition and DNA encoding. Security analysis confirms that the encrypted images have pixel correlation coefficients below 0.01 in horizontal, vertical, and diagonal directions, information entropy greater than 7.999, and a key space of 22080. These results verify the excellent encryption performance and reliability of the proposed scheme and the generated sequences.
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Dual-wavelength lasers in the EUV (extreme ultraviolet) band can be applied in many fields such as high-resolution imaging, EUV nonlinear optics, and high-density plasma diagnostics. In this paper, the 46.9 nm and 69.8 nm dual-wavelength laser of Ne-like Ar (Ar8+) ion pumped by capillary discharge has been obtained. In order to realize to change the amplitude of the main pulse current over a wide range, several parameters of the main pulse power supply such as charging voltage of the Marx generator, the conduction voltage of the spark gap switch, and the conductivity of the deionized water in the Blumlein transmission line, have been adjusted to vary the amplitude of the main pulse current from 8.4 kA to 15.8 kA. On this basis, the influence of the initial argon pressure and the main pulse current amplitude on the intensities of 46.9 nm and 69.8 nm lasers were studied. The experimental results show that there is an optimum pressure under every main pulse current amplitude. The optimum pressures for 69.8 nm laser are lower than those for the 46.9 nm laser. Based on the variation of laser intensity with the initial pressure and the main pulse current amplitude, the optimal experimental parameters for the 46.9 nm laser are current of 10.9 kA and initial pressure of 18.1 Pa and those for the 69.8 nm laser are current of 14.5 kA and initial pressure of 18.5 Pa. When the main pulse current amplitude is 14.5 kA and the initial pressure is 18.5 Pa, the dual-wavelength laser with both strong 46.9 nm and 69.8 nm laser can be obtained. The different influencing rules of the initial pressure and the main pulse current on the 46.9nm and 69.8nm lasers can guide other groups to explore the possibility of achieving 69.8 nm laser by using the existing 46.9 nm laser device. Meanwhile, the research on the optimal parameters of 46.9 nm and 69.8 nm lasers is benefit to enhance the energy of lasers and expand their application fields. One of future studies will focus on the applications of the dual-wavelength laser in sum frequency and difference frequency of EUV lasers.
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Cavity optomechanical systems have become a topic of great interest in recent years, and the coupled-cavity model is also a classic theoretical framework. This paper aims to construct a coupledcavity optomechanical system to study induced transparency, Fano resonance, and fast-slow light effects in such a system. By transferring phenomena typically studied in a single optical cavity to a coupled-cavity system, we analyze specific phenomena detected in optical and microwave cavities, such as transmission and absorption spectra, to investigate induced transparency. We also examine Fano resonance in the model by varying detuning, and study fast-slow light effects through group velocity. This paper first constructs the corresponding physical model, as shown in Figure 1. Based on the theoretical model, a reasonable Hamiltonian is proposed. By introducing appropriate dissipation and fluctuation noise terms, the Langevin equations of motion are derived. Next, the Langevin equations are linearized, and the resonant terms are retained to obtain O+ . The amplitude of the field modes is then derived using the input-output relations. Following the experimental data from referenced literature, a numerical simulation program is implemented in Mathematica. By substituting the relevant parameters and performing calculations, the results are obtained through simulation. For the first time, the interactions among photons, magnons, microwaves, and phonons— as well as the interplay between photons in the two cavities—are investigated in a coupled cavity optomagnomechanical system. Electromagnetically induced transparency (EIT), Fano resonance, and fast-slow light effects are studied in this coupled-cavity optomagnomechanical framework. Phenomena typically examined in a single optical cavity are extended to the coupled-cavity system, with specific observations analyzed separately in the optical and microwave cavities. When δ=ωb, the absorption spectrum splits, and the absorption peak decreases from its maximum to its minimum. This phenomenon arises from the disruption of quantum interference effects. The resonance condition suppresses the generation of Fano resonance. At the resonant frequency ω0, the group delay is greater than zero, indicating slow-light propagation, and this effect is enhanced with increasing coupling strength. Additionally, a group delay of τ is achieved. Meanwhile, on either side of the resonant frequency, the group delay peaks exhibit a decreasing positive value and an increasing negative value, respectively, signifying a gradual weakening of the slow-light effect and a corresponding enhancement of the fast-light effect. This paper investigates the MIT, MMIT, and OMIT windows in a coupled-cavity optomagnomechanical (OMM) system under a strong control field and weak probe field. The MMIT phenomenon is observed through nonlinear phonon-magnon interactions. Additionally, the photon-magnon interaction in the microwave cavity leads to MIT, while OMIT is achieved via the radiation pressure interaction between photons and nonlinear phonons in the optical cavity. The frequency of the probe field is tuned to interact with both the microwave and optical cavities. When the probe field couples with the microwave cavity, its absorption at the resonant frequency is significantly suppressed under optomechanical coupling, resulting in a pronounced optical switching effect on transmission. We analyze the asymmetric Fano resonance phenomenon, which reflects the existence of quantum interference mechanisms within the system and influences the fast- and slow-light conversion processes. Furthermore, by selecting appropriate coupling parameters, not only can the fast- and slow-light effects be enhanced, but dynamic switching between them can also be achieved.
Abstract +
This work presents a Rydberg-atom-based Loran-C receiver designed to overcome long-standing limitations of conventional systems, including low sensitivity and bulky form factors. In the proposed design, a reference electrode couples the low-frequency Loran-C signal into an atomic vapor cell equipped with integrated parallel plates; an auxiliary DC bias field is applied to optimize this coupling. By leveraging electromagnetically induced transparency (EIT) in conjunction with the Stark effect, the receiver enables direct, high-sensitivity measurement of the electric field's amplitude and phase. An FPGA-based acquisition stage and a MATLAB signal-processing pipeline were implemented to perform ground-wave/sky-wave discrimination, time-difference-of-arrival (TDOA) estimation, position fixing, and timing recovery. Experimental results confirm that the Rydberg-atom-based receiver successfully provides both positioning and timing capabilities. These findings demonstrate that Rydberg-atom sensors can significantly enhance the sensitivity and dynamic range of Loran-C systems at low frequencies, thereby establishing a quantum-sensing pathway toward next-generation, high-reliability navigation and timing architectures.
Abstract +
Bound states in the continuum (BIC) has made significant progress in photonic integrated circuits, but there are still some limitations in practical applications. When the mode deviates from the BIC, its Q value decays rapidly. These limit the performance of BIC under wide-angle incidence. The application limitation of BIC is mainly because all types of BIC are discrete mode points in the k-space. This kind of point-like BIC or quasi-BIC, on the one hand, has extremely high requirements for the incident angle; even a slight deviation can cause a sharp drop in the Q factor. On the other hand, it is also extremely sensitive to the geometric parameters of the structure (such as the size, position and offset of the holes). Even the slightest manufacturing error can cause the formant position to shift and the Q value to drop sharply. Therefore, if we can construct a BIC in a continuous k-space, we can largely remove the constraints on the application of traditional BIC. In this work, we designed a simple photonic crystal slab and performed calculations and analyses of its band structure and quality factor. By optimized the structural parameters, a square-shaped quasi-BIC loop with tunable side length was identified in k-space. Based on the relationship between the quasi-BIC loop and the equifrequency contours, together with the characteristics of the mode field distribution, it was revealed that this square-shaped quasi-BIC originates from the effect of total internal reflection and standing-wave resonances in the structure. The existence of the square-shaped quasi-BIC loop is further confirmed by the Fano spectral line with high quality factors at a special incident angle or frequency which corresponds to the position of the quasi-BIC loop. The square-shaped quasi-BIC loop provides a large anglebandwidth response and expand the applied range of BIC.
, , Received Date: 2025-05-25
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The Stark effect in Rydberg atoms exhibits remarkable sensitivity to external electric fields, thus forming the fundamental basis for precision electric field measurements. This study systematically and comprehensively investigates the regulatory effects of DC and AC electric fields on cesium Rydberg atoms, both experimentally and theoretically. Utilizing a two-photon three-level system, we generate 28D5/2 Rydberg states and establish electromagnetically induced transparency (EIT) as the macroscopic observable. Our experimental results demonstrate distinct Stark splitting patterns under DC fields, revealing three fine-structure states each with polarization-dependent frequency shift,they being the negative polarizability states (mj = 1/2, 3/2) exhibiting rightward shifts, and the positive polarizability state (mj = 5/2) showing leftward displacement. For power-frequency AC fields (50 Hz), we observe characteristic double-frequency modulation of the EIT-Stark spectra, with measurement limitations emerging at field strengths above 24 V/cm due to laser scanning range constraints. To overcome this limitation, we develop an innovative DC field regulated measurement scheme, establishing a dynamic model for the combined AC/DC field interaction with Rydberg atoms. The model successfully derives demodulation expressions for extracting both DC and AC field components from the composite spectral shifts. Experimental validation shows that applying an 8 V/cm DC bias field can extend the measurable AC field range to 32 V/cm, achieving a 33.3% improvement over direct measurement methods within a 1 GHz laser scanning range, while maintaining exceptional accuracy with demodulation errors below 0.8% across all tested configurations. The detailed error analysis reveals that the measurement precision improves with the increase of field strength, with a standard deviation of σ = 0.2196%, demonstrating the robustness of our approach. Compared with existing techniques, this DC-field regulation method effectively addresses the critical challenge of limited laser scanning range in strong-field measurements, while preserving the quantum advantages of Rydberg atom sensors. The research provides both theoretical foundations and practical solutions for measuring power-frequency strong electric fields in power systems, with potential applications extending to other low-frequency strong-field measurement scenarios. Future work will focus on enhancing measurement stability in extreme field conditions, improving accuracy, and further expanding the operational range of this quantum sensing technology.
, , Received Date: 2025-07-01
Abstract +
The viscosities of matters under extreme conditions, i.e. warm dense matter (WDM) and hot dense matter (HDM), have significant applications in various fields, such as the design of inertial confinement fusion targets, the astrophysical structure evolution, and the interfacial instability and mixing development under extreme conditions. Since the temperature and pressure ranges accessible by experimental techniques for viscosity measurement are very limited, the acquisition of viscosity data under extreme conditions mainly relies on theoretical calculations. This work introduces a variety of molecular dynamics (MD) methods and models for calculating the viscosities of WDM and HDM, they being quantum MD (QMD), orbital-free MD (OFMD), average atom model combined with hypernetted chain (AAHNC), effective potential theory combined with average atom model (EPT+AA), hybrid kinetics MD (KMD), integrated Yukawa viscosity model (IYVM), Stanton-Murillo transport model (SMT), pseudo-ion in jellium (PIJ), one-component plasma model (OCP), and random-walk shielding-potential viscosity model (RWSP-VM). Simultaneously, the viscosities of various elements obtained by these methods are shown, ranging from low to high atomic number (Z), i.e., H, C, Al, Fe, Ge, W, and U. The accuracy and the applicability of each method are analyzed in detail by comparison. RWSP-VM, which is based on physical modeling and independent of MD data, has comparable accuracy to simulation data over a wide range of temperature and pressure, and is an efficient method of obtaining viscosity data of WDM and HDM. This work will pave the way for calculating the shear viscosities under extreme conditions, and may play an important role in promoting the relevant applications. The data calculated from RWSP-VM in this work are openly available at https://doi.org/10.57760/sciencedb.j00213.00180 .
, , Received Date: 2025-09-22
Abstract +
In order to investigate the enhancement mechanism of atmospheric-pressure oxygen pulsed discharge in a parallel-plate dielectric barrier discharge (DBD) with microstructures fabricated on the dielectric surface of the high-voltage electrode, this work systematically analyzes the electron transport processes, the formation and evolution of electric fields, and the spatial distribution of particles by using a two-dimensional fluid model. The introduction of microstructures can cause significant electric field distortion, generating a strong transverse electric field that locally confines and focuses electrons beneath the micro-structured region, leading to the formation of a stable corona-mode discharge.At the same time, the reduced local discharge gap near the microstructure enhances the longitudinal electric field, resulting in a temporal asynchrony between the corona discharge under the microstructure and the parallel-plate discharge in the adjacent flat regions. As the geometric dimensions of the microstructures increase, a secondary discharge is triggered, further modulating the overall discharge behavior. Under conditions where the corona discharge is suppressed by higher protrusions, the occurrence of secondary discharge effectively increases the proportion of high-energy electrons and the spatially averaged density of reactive oxygen atoms. Simulation results reveal that the corona discharge and the secondary discharge significantly raise electron density, electron temperature, and the proportion of high-energy electrons, thereby intensifying the discharge activity. These findings offer deep insight into the micro-mechanisms of microstructure-induced discharge enhancement and provide valuable guidance for designing highly efficient plasma devices with tailored geometric features.
, , Received Date: 2025-08-15
Abstract +
Memristors exhibit controllable nonlinear characteristics, generating chaotic signals that are characterized by randomness, sensitivity, and unpredictability, thereby demonstrating significant potential applications in information encryption and signal processing. With the integration of chaos theory and electronic technology, constructing memristive hyperchaotic systems has become a hot topic in nonlinear science and information security. To overcome the limitation of monotonic dynamic characteristics in traditional chaotic systems, we design a novel memristor-based hyperchaotic system with richer dynamic behavior and higher application value in this paper. Moreover, the characteristic analysis, theoretical verification, application exploration, and hardware implementation are conducted to support the engineering applications of the system. Building upon the classical Chen system, this work is innovatively combined with a cubic nonlinear magnetically controlled memristor model as a feedback element. By establishing a mathematical model of the memristor and coupling it with the state equations of the Chen system, we design a four-dimensional memristor-based hyperchaotic system. First, by integrating numerical computation with differential equation theory, a comprehensive mathematical model is established to analyze fundamental properties, such as symmetry and dissipativity, thereby validating the system's rationality. Second, the system’s dynamical behaviors are analyzed, including attractor phase diagrams, Lyapunov exponents, power spectra, parameter effects, transient dynamics, and coexisting attractors. Simultaneously, variational methods are utilized to analyze unstable periodic orbits within the system. A symbolic coding approach based on orbital characteristics is established to convert orbital information into symbolic sequences, and orbital pruning rules are explored to provide a basis for optimal orbital control. Furthermore, a digital image encryption method is proposed based on this system. Using chaotic sequences as keys, image pixels are scrambled and diffused. The effectiveness of encryption is validated through histogram analysis, correlation analysis, information entropy evaluation, and testing of anti-attack capabilities. Finally, a DSP-based digital circuit hardware platform is constructed to run the system, and the hardware experimental results are compared with software simulation outcomes. These findings reveal that the introduction of memristors induces linearly distributed equilibrium points in phase space, generating hidden attractors that enrich the chaotic behavior of the system. The simulation of dynamic behavior confirms the rich dynamics of this four-dimensional memristor-based hyperchaotic system. The proposed digital image encryption method demonstrates robust security performance. The DSP hardware experiments and software simulations yield highly consistent attractor phase diagrams, validating the correctness and feasibility of the system.
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Abstract +
Polymer-dispersed liquid crystal (PDLC) gratings, as an emerging optical material, offer significant advantages such as low fabrication cost, suitability for large-area processing, and rapid electro-optic response. They show great potential in holographic waveguide displays and optical interconnection systems, where they are often used as key beam-splitting and coupling components. However, most current beam-splitting devices based on PDLC materials are limited to generating 2×2 diffraction arrays, which considerably restricts their ability to achieve multi-channel and multi-order light field modulation, thereby failing to meet the growing demands of high-dimensional optical information processing.
To overcome this limitation, this study proposes a fabrication scheme for two-dimensional PDLC gratings based on holographic multi-beam interference. First, starting from holographic interference theory, we rigorously derived the light intensity distribution function of the multibeam interference field. Second, a physical model of a volume holographic transmission grating with a refractive index distribution matching the interference field intensity was constructed using the finite element analysis software COMSOL Multiphysics. Utilizing this model, we simulated and optimized the final diffraction performance by varying key fabrication parameters, such as the exposure intensity ratio between the reference and object beams and the grating layer thickness.
During the experimental validation phase, we successfully fabricated a one-dimensional PDLC grating using a symmetrical three-wave interference exposure method. Under normal incidence with a 532 nm laser, the fabricated one-dimensional PDLC grating demonstrated symmetric diffraction, with the pair of first-order beams both exhibiting a diffraction efficiency exceeding 44%, thereby preliminarily verifying the reliability of the model. Building on this foundation, we further designed an innovative five-wave interference exposure setup. Using a custom-made quadrilateral pyramid beam splitter, we achieved five-beam interference and successfully prepared a two-dimensional PDLC grating that met the design specifications. Test results demonstrate that under normal incidence at 532 nm, this two-dimensional grating produces a 3×3 two-dimensionaldiffraction array. The 1st-order diffraction angle is 18.4°, and the beamsplitting energy ratio of each single 1st-order diffracted light exceeds 10%, achieving efficient energy distribution.
To overcome this limitation, this study proposes a fabrication scheme for two-dimensional PDLC gratings based on holographic multi-beam interference. First, starting from holographic interference theory, we rigorously derived the light intensity distribution function of the multibeam interference field. Second, a physical model of a volume holographic transmission grating with a refractive index distribution matching the interference field intensity was constructed using the finite element analysis software COMSOL Multiphysics. Utilizing this model, we simulated and optimized the final diffraction performance by varying key fabrication parameters, such as the exposure intensity ratio between the reference and object beams and the grating layer thickness.
During the experimental validation phase, we successfully fabricated a one-dimensional PDLC grating using a symmetrical three-wave interference exposure method. Under normal incidence with a 532 nm laser, the fabricated one-dimensional PDLC grating demonstrated symmetric diffraction, with the pair of first-order beams both exhibiting a diffraction efficiency exceeding 44%, thereby preliminarily verifying the reliability of the model. Building on this foundation, we further designed an innovative five-wave interference exposure setup. Using a custom-made quadrilateral pyramid beam splitter, we achieved five-beam interference and successfully prepared a two-dimensional PDLC grating that met the design specifications. Test results demonstrate that under normal incidence at 532 nm, this two-dimensional grating produces a 3×3 two-dimensionaldiffraction array. The 1st-order diffraction angle is 18.4°, and the beamsplitting energy ratio of each single 1st-order diffracted light exceeds 10%, achieving efficient energy distribution.
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