Accepted
, , Received Date: 2025-08-21
Abstract +
Gold nanorods (AuNRs) have become highly promising biomedical probes due to their tunable plasmonic properties, but their real-time, high-resolution imaging of subcellular behavior, particularly their orientation dynamics reflecting critical nano-bio interactions, is hindered by the diffraction limits and drawbacks of existing super-resolution methods, such as reliance on high-intensity lasers and exogenous labeling. To solve this problem, we develop coherent modulation amplitude projection imaging (CMAPI), a novel label-free technique that uses spatially and temporally modulated pairs of femtosecond pulses to coherently control the two-photon photoluminescence (TPPL) of AuNRs. By using AuNRs as three-level systems with a measurable intermediate state, CMAPI encodes sub-diffraction-limit spatial and orientational information into the frequency domain through precise manipulation of inter-pulse delay, phase, and polarization. Experimental results confirm the nonlinear excitation nature of AuNRs, with single-pulse polarization response following a cos2θ dependence. Under two-pulse excitation, the emission exhibits obvious coherence-dependent behavior: at zero delay, the response is controlled by quantum superposition; under a delay that matches the intermediate state lifetime (0.5 ps), the three-level model accurately describes the response; under a longer delays (10 ps), the system returns to incoherent emission. CMAPI retrieves nanoscale information through Fourier analysis of photon arrival times, producing simultaneous amplitude and phase images that reveal AuNRs’ precise positions (about 60 nm localization precision), in-plane orientations (e.g. quadrant-specific arrangement inferred from phase sign), and local environmental coupling, such as plasmon-induced phase jumps, all under ultralow excitation power (<5 μW/μm2) to avoid light damage. This approach enables visualization of features beyond the diffraction limit, distinguishing multiple AuNRs within a single diffractive spot, as validated by scanning electron microscopy. CMAPI provides a powerful, non-invasive platform for quantifying dynamic biological processes involving anisotropic nanoparticles. These process include conformational shifts during endocytosis, torque transmission in molecular motors, and real-time tracking of nanoscale interactions, thereby offering profound insights into theranostic probe design and fundamental biophysical research.
, , Received Date: 2025-08-29
Abstract +
, , Received Date: 2025-08-08
Abstract +
Multiphoton microscopy (MPM) has become an essential research tool in biomedicine. Current MPM systems predominantly rely on Ti:sapphire lasers provided tunable femtosecond pulses at 720–950 nm. To access the second biological transparency window (1000–1350 nm), complex optical parametric oscillators are typically required. urthermore, sources operating in the third biological transparency window (1600–1750 nm) are attracting significant attention for enhanced imaging depth. However, no ultrafast laser source simultaneously covering all three transparency windows exists, thus hindering the widespread application of MPM in life sciences. Here, we demonstrate a fiber-laser-based ultrafast source that generates four-color tunable pulses across 800–1650 nm, covering the full spectral range for multiphoton excitation. This source utilizes our proposed spectral selection technique via self-phase modulation (SESS). SESS ensures SPM-dominated spectral broadening, producing isolated spectral lobes. Filtering the outermost lobes will generate near-transform-limited pulses with broad wavelength tunability. Using this supercontinuum excitation source, we successfully realize label-free imaging of diverse biomedical specimens, validating the performance of MPM empowered by this novel driving source.
, , Received Date: 2025-08-06
Abstract +
In order to better understand and predict the complex interface instability phenomena induced by non-uniform shock waves in practical engineering and scientific applications, a detailed investigation has been conducted on the interaction between a Mach reflection wave configuration and a planar gas interface. Particular attention is paid to the role of the Mach stem scale in governing the evolution of interface instability and the associated mechanisms of perturbation growth. Numerical simulations show that when the Mach reflection wave configuration interacts with the interface, the complex wave structures impart initial velocity perturbations onto the interface, thereby triggering instability. This process is further influenced by the non-uniform post-shock flow field, under which the initially perturbed interface gradually evolves into a concave cavity and subsequently into jet-like bubble structures. These patterns are notably different from the spike and bubble morphologies observed in classical Richtmyer-Meshkov instability. A systematic quantitative analysis of the perturbation amplitude reveals that the instability growth can be divided into two different stages: an initial linear growth stage and a nonlinear development stage. The transition between these stages is governed by interface deformation mechanisms, particularly the bending of the slip line intersecting the interface and the subsequent formation of the curl-up jet. When the shock strength and incidence angle of the Mach reflection configuration are kept constant, the Mach stem scale emerges as the decisive parameter controlling the characteristic time of slip line curling and jet development. The results show that during the linear stage, perturbation growth is primarily determined by shock strength and incidence angle, and is insensitive to the Mach stem scale. In contrast, during the nonlinear stage, the perturbation growth rate increases with the augmentation of Mach stem scales, highlighting the scale-dependent nature of the nonlinear stage. Furthermore, theoretical models are critically examined against numerical simulation results. While existing models can reasonably capture the initial velocity perturbations imprinted on the interface by the Mach reflection configuration, they are unable to combine the effects of Mach stem scale and the sustained driving influence of post-shock flow non-uniformities. This limitation underscores the need for improved theoretical descriptions. Overall, these findings provide new insights into the intrinsic coupling among shock strength, incidence angle, and Mach stem scale in determining the evolution of shock-induced interface instability. These insights not only deepen the fundamental understanding of Richtmyer-Meshkov-type instabilities in non-classical regimes but also provide valuable references for the development of predictive theoretical models and also for engineering applications such as inertial confinement fusion and high-speed propulsion systems.
, , Received Date: 2025-08-05
Abstract +
In radio-frequency capacitively coupled dusty plasma discharge, the grooves on the lower electrode plate significantly modify the electric potential distribution in the sheath region, thereby influencing the collective dynamic behavior of dust particles. Experimentally, when micrometer-sized dust particles are injected into the discharge chamber, a distinct layer of dust particles forms above the groove-induced potential well, exhibiting a characteristic bowl-shaped cloud structure. The volume of the dust cloud shows a strong dependence on RF power and discharge pressure. As power increases or pressure decreases, the dust cloud moves upward due to the influence of axial force on the particles. Besides, dust voids form in the middle of each dust layer, and their diameter evolution is influenced by particle number, RF power, and pressure. Particularly, when the diameters of the electrode grooves are small, the diameters of the dust voids first increase, then decrease and finally disappear as discharge pressure increases. Furthermore, a three-dimensional hybrid model is theoretically established. This model couples a fluid model with a dust particle model to explain the collective behavior of dust particles. This behavior is governed by the resultant axial force which includes axial electric field force, ion drag force, and gravity, as well as the resultant radial force, which consides radial electric field force and ion drag force. It is also found that in the DC-overlapped RF plasma, the suspension height of dust particles first increases and then decreases as the negative DC bias is increased. The change in dust particle height can reflect the transition of plasma discharge from α-model to γ- mode.
, , Received Date: 2025-08-25
Abstract +
, , Received Date: 2025-08-22
Abstract +
The liquid phase serves as a critical environment for chemical and biological reactions. The chemical and biological reaction dynamics of molecules in liquids exhibit evolution behaviors that are significantly different from those of isolated molecules in the gas phase. The in-depth investigation of the ultrafast excited-state dynamics of liquid-phase molecules is of great importance for uncovering the microscopic mechanisms underlying complex chemical and biological processes. Photoelectron spectroscopy not only reveals the electronic structure of excited-state molecules but also exhibits high sensitivity to structural changes, making it a powerful tool for studying the relaxation dynamics. Liquid-phase time-resolved photoelectron spectroscopy utilizes a liquid microjet within a high vacuum. In this pump-probe technique, an initial pump pulse excites the liquids to initiate dynamics, followed by a delayed probe pulse that ionizes the evolving system. The time-dependent energy distribution of the resulting photoelectrons, which encodes the ultrafast dynamics, is measured by a magnetic-bottle time-of-flight (TOF) analyzer. This review systematically summarizes recent advancements in the time-resolved liquid-phase photoelectron spectroscopy technology for studying ultrafast dynamics in liquids, detailing the fundamental working principles of magnetic-bottle spectrometers and the preparation techniques for liquid microjet targets. Furthermore, typical applications are discussed, concluding with an analysis of current technical challenges and future research directions.
, , Received Date: 2025-08-19
Abstract +
Luminescence and anisotropy in two-dimensional (2D) materials have important implications for both fundamental material physics and potential applications such as polarized light-emitting devices. However, many natural-occuring 2D materials typically exhibit either luminescence or anisotropy, but not both. In this work, we utilize van der Waals (vdW) engineering to construct a heterostructure (HS) with anisotropic luminescent properties, which is composed of isotropic monolayer (1L) MoS2 (with strong intrinsic luminescence) and low-symmetry NbIrTe4 (strong anisotropy without photoluminescence). Experimentally, we characterize the optical response of the HS by using angle-resolved PL spectroscopy. The results indicate that the intrinsic anisotropic potential field of NbIrTe4 at the interface effectively breaks the in-plane isotropic symmetry of MoS2, inducing a pronounced polarization-dependent emission of A and B excitons. The anisotropy ratio is enhanced to ~1.58, corresponding to a linear polarization degree of approximately 22%. This work provides new insights into 2D interfacial coupling and offers useful guidance for the design and engineering of next-generation high-performance, tunable polarized light-emitting devices.
, , Received Date: 2025-08-09
Abstract +
Owing to, Solid-state batteries have gradually become the focus of people's attention and research in recent years due to the advantages of high energy density and high safety factor. Lithium dendrites are a key factor affecting battery safety and service life, and in severe cases, battery short circuits can occur. Compared with liquid batteries, solid-state batteries rely on solid-state electrolytes with higher mechanical strength, which can effectively inhibit the growth of lithium dendrites, but with the increase of the number of charge-discharge cycles, the dead lithium produced by the incomplete dissolution of lithium dendrites gradually accumulates, and the performance of the battery gradually decreases. In this work, the problem of dead lithium in solid-state batteries is studied by using COMSOL Multiphysics 6.2 finite element simulation software. Due to the fact that existing research on dead lithium mainly focuses on phase field models combined with binary physics, there is little research on the influence of electrochemical parameters on dead lithium. Therefore, the phase field method is used to simulate the dissolution of lithium dendrites and the formation of dead lithium under the coupling of force-thermal-electrochemical fields. When the heat transfer model is coupled, the difference in the morphology of dead lithium before and after the coupled heat transfer model is further studied by applying an external pressure to change the stress of lithium dendrites. When the coupled mechanical field changes, the morphology of dead lithium before and after the coupled mechanical field is further studied by changing the temperature magnitude. At the same time, the effects of changes in three electrochemical parameters, namely diffusion coefficient, interfacial mobility and anisotropic strength, on the area of dead lithium are also explored. The research results indicate that when the heat transfer model or mechanical field is coupled into the phase field model, the dendrite dissolution cut-off time and dead lithium area will change. When the base rises at high temperature or when low external pressure or high external pressure is applied, the area of dead lithium decreases. For changing the electrochemical parameters, reducing the diffusion coefficient, increasing the interfacial mobility and reducing the anisotropic strength can effectively reduce the area of dead lithium.
, , Received Date: 2025-09-08
Abstract +
The charge transfer cross sections of collisions between He ions in the solar wind and H2O molecule constitute essential data required for the astrophysical plasma modeling. However, experimental measurements of single charge transfer (SCT) cross sections for He+-H2O collisions at low-to-intermediate energies (corresponding to the velocity range of the solar wind) are extremely scarce, and first-priciple theoretical calculations have not been conducted. In this study, employing the time-dependent density functional theory nonadiabatically coupled with the molecular dynamics, the SCT cross sections are calculated for He+-H2O collisions over a broad energy range of 1.33–1800 keV. An inverse collision framework is used to investigate the charge transfer dynamics and electron-ion coupling processes. It is found that the SCT cross section exhibits a strong dependence on the molecular orientation. Furthermore, there are significant differences in the contributions of different molecular orientations to the cross section between low-energy and high-energy regions. The computed cross section results show good agreement with the existing data obtained from experiments and classical theoretical models. This indicates that the present theoretical method and numerical framework are not only applicable to handling the charge transfer processes in collisions between dressed ions and molecules but also enable the quantitative analysis of the effect of molecular orientation on the cross section. This study lays a foundation for cross section calculations of complex collision systems. The datasets presented in this paper are openly available at https://doi.org/10.57760/sciencedb.j00213.00193 .
, , 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.
,
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.
,
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.
,
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.
,
Abstract +
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.
- 1
- 2
- 3
- 4
- 5
- ...
- 15
- 16
