Collision off-axis position dependence of relativistic nonlinear Thomson inverse scattering of an excited electron in a tightly focused circular polarized laser pulse

This paper presents a novel view of the impact of electron collision off-axis positions on the dynamic properties and relativistic nonlinear Thomson inverse scattering of excited electrons within tightly focused, circularly polarized laser pulses of varying intensities. We examine the effects of the transverse ponderomotive force, specifically how the deviation angle and speed of electron motion are affected by the initial off-axis position of the electron and the peak amplitude of the laser pulse. When the laser pulse intensity is low, an increase in the electron's initial off-axis distance results in reduced spatial radiation power, improved collimation, super-continuum phenomena generation, red-shifting of the spectrum's harmonic peak, and significant symmetry in the radiation radial direction. However, in contradiction to conventional understandings,when the laser pulse intensity is relatively high, the properties of the relativistic nonlinear Thomson inverse scattering of the electron deviate from the central axis, changing direction in opposition to the aforementioned effects. After reaching a peak, these properties then shift again, aligning with the previous direction. The complex interplay of these effects suggests a greater nuance and intricacy in the relationship between laser pulse intensity, electron position, and scattering properties than previously thought.

Design of a freeform,dual fields-of-view,dual focal lengths,off-axis three-mirror imaging system with a point-by-point construction-iteration process

In this Letter,we propose a novel configuration and design method of freeform,dual fields-of-view(FOVs),dual focal lengths,off-axis three-mirror zoom imaging systems.The switch of the two zooms is achieved by rotating a single mirror element.The design of a freeform,dual focal lengths zoom system is realized by a point-by-point design approach for the first time to our knowledge.This method enables the direct design of freeform surfaces from initial planes using given system specifications and configuration,and the designed system can be taken as a good starting point for further optimization.A freeform,dual FOVs,dual focal lengths,off-axis three-mirror zoom system is demonstrated.The F-numbers of the two zooms are 2 and 2.4.The dual FOVs are 3°×3°and2.5°×2.5°.After final optimization,both of the zooms achieve high performances.

Simultaneous detection of CH_(4)and CO_(2)through dual modulation off-axis integrated cavity output spectroscopy

This study established a novel method for the simultaneous detection of two-component gases.Radio frequency(RF)white noise disturbance laser current and wavelength modulation were simultaneously used to improve the off-axis integrated cavity output spectroscopy technique,and a high-precision dual modulation OA-ICOS(RF-WM-OA-ICOS)system was established.The two laser beams were coupled into one laser beam that was applied incident to the cavity of RF-WM-OA-ICOS system.The second harmonic signals of CH_(4)and CO_(2)gas simultaneously appeared in the rising or falling edge of a triangular wave.This method was used to measure CH_(4)and CO_(2)with different concentrations.The results indicated that the proposed system has high stability and can accurately and simultaneously measure the concentrations of CH_(4)and CO_(2),with an optimal integration time of 220 s.The minimum detection limit was 10 ppb for CH_(4)and 1.5 ppm for CO_(2).The corresponding noise equivalent absorption sensitivity values were calculated as 2.67×10^(-13)cm^(-1)·Hz^(-1/2)and 5.18×10^(-11)cm^(-1)·Hz^(-1/2),respectively.The proposed dual-component gas simultaneous detection method can also be used for high-precision simultaneous detection of other gases.Therefore,this study may serve as a reference for developing portable multicomponent gas analyzers.

Characteristic Analysis of Off-Axis Meta-Lens

Meta-lens are a new type of planar optical element that can flexibly manipulate the phase, polarization and amplitude of the beam, and are currently receiving a great deal of attention as they are easier to process and manufacture. Off-axis meta-lens are a special type of meta-lens with a certain degree of dispersion that can be used as a beam-splitting element, providing a unique and feasible way to realize micro-miniature instruments. We analyze the effects of different numerical apertures and off-axis angles on the spectral resolution, focusing efficiency and simulation results of off-axis meta-lens to provide ideas for subsequent research and application of off-axis meta-lens. A number of off-axis meta-lens with parameters NA = 0.408 α = 13°, NA = 0.18 α = 13° and NA = 0.408 α = 20° were simulated through Lumerical software. The results show that the off-axis angle is related to the resolution;the larger the angle, the better the spectral resolution but the lower the focusing efficiency;when the numerical aperture is smaller, the smaller the coverage of the phase distribution, which will lead to a larger deviation between simulation and theory. The designer needs to balance the numerical aperture, off-axis angle and other parameters reasonably according to the requirements in order to achieve the desired effect. The findings of this study have important reference values for the theoretical analysis of off-axis meta-lens and the design of parameters in practical applications. .

Far-field vector-diffraction of off-axis parabolic mirror under oblique incidence

Based on a full vector-diffraction theory, a detailed theoretical study is carried out, aiming at providing a clear insight into the effects of different focusing and off-axis parabola parameters on far-field vector-diffraction properties of an offaxis parabolic mirror in the presence of misalignments of the incoming beam. The physical origin of these effects is also explored. The results show that the far-field intensity profile is altered by the distortion-, coma-, and astigmatism-like aberrations, which are caused by oblique incidence rather than inherent aberrations for the off-axis configuration. The radius of 90% encircled energy also increases but does not change monotonically with incident beam size increasing, or rather,it first decreases and then increases. The focal shift strongly depends on the effective focal length and oblique incidence angle, but it is almost independent of the beam size, which affects the focusing spot patterns. The intensity distribution produces a higher astigmatic image with off-axis angle increasing. Coma-like aberration starts to become dominant with beam size increasing and results in larger curved propagation trajectory. The incident polarization also affects the intensity distribution. The variation in the Strehl ratio with oblique incidence angle strongly depends on the misalignment direction and beam size as well. In addition, we find that the difference in locus between the catacaustic and the diffraction focus in the meridian is small. But the locus of the sagittal foci is obviously different from the locus of the meridian foci and the catacaustic focus. Moreover, the peak intensity of the sagittal focus is maximum, and the ratio of the peak intensity to that in the meridian plane is approximately 1.5. Understanding these effects is valuable for assessing a practical focused intensity and describing the motion of charged particles under a strong electric field in ultraintense laser–matter interaction.

Off-axis multi-wavelength dispersion controllingmetalens for multi-color imaging

Dispersion control is crucial in optical systems,and chromatic aberration is an important factor affecting imaging quality in imaging systems.Due to the inherent property of materials,dispersion engineering is complex and needs to trade off other aberration in traditional ways.Although metasurface offers an effective method to overcome these limits and results in well-engineered dispersion,off-axis dispersion control is still a challenging topic.In this paper,we design a single-layer metalens which is capable of focusing at three wavelengths(473 nm,532 nm,and 632 nm)with different incident angles(0°,-17°and 17°)into the same point.We also demonstrate that this metalens can provide an alternative for the bulky color synthetic prism in a 3-chips digital micromirror device(DMD)laser projection system.Through this approach,various off-axis dispersion controlling optical devices could be realized.

Optical Design for the Off-axis Reflective Optics with Wide Field

Reflective optics with wide field of view has been applied more and more widely in EUVL or space optics, and also plays an important role in promoting scientific and technological research. Among the reflective optics, the off-axis reflective optics is the most hopeful solution to the ever-highest demands of these applications. This paper gives the requirements of both the above mentioned applications and the similarities and differences between these two kinds of optical systems. Finally, a design example of off-axis reflective optics with wide field of view is presented and described.

Properties of off-axis hollow Gaussian–Schell model vortex beam propagating in turbulent atmosphere

The analytical expression of off-axis hollow Gaussian–Schell model vortex beam(HGSMVB)generated by anisotropic Gaussian–Schell model source is first introduced.The evolution properties of off-axis HGSMVB propagating in turbulent atmosphere are analyzed.The results show that the off-axis HGSMVB with smaller coherence length or propagating in stronger turbulent atmosphere will evolve from dark hollow beam into Gaussian-like beam with a larger beam spot faster.The beams with different values of integer order N or the position for hollow and vortex factor R will have almost the same Gaussian-like spot distribution at the longer propagation distance.

Study of structure-property relationship of semiconductor nanomaterials by off-axis electron holography

As the scaling down of semiconductor devices, it would be necessary to discover the structure-property relationship of semiconductor nanomaterials at nanometer scale. In this review, the quantitative characterization technique off-axis electron holography is introduced in details, followed by its applications in various semiconductor nanomaterials including group IV, compound and two-dimensional semiconductor nanostructures in static states as well as under various stimuli. The advantages and disadvantages of off-axis electron holography in material analysis are discussed, the challenges facing in-situ electron holographic study of semiconductor devices at working conditions are presented, and all the possible influencing factors need to be considered to achieve the final goal of fulfilling quantitative characterization of the structure-property relationship of semiconductor devices at their working conditions.

Image Motion Compensation of Off-Axis TMA Three-Line ArrayAerospace Mapping Cameras

To enhance the image motion compensation accuracy of off-axis three-mirror anastigmatic( TMA)three-line array aerospace mapping cameras,a new method of image motion velocity field modeling is proposed in this paper. Firstly,based on the imaging principle of mapping cameras,an analytical expression of image motion velocity of off-axis TMA three-line array aerospace mapping cameras is deduced from different coordinate systems we established and the attitude dynamics principle. Then,the case of a three-line array mapping camera is studied,in which the simulation of the focal plane image motion velocity fields of the forward-view camera,the nadir-view camera and the backward-view camera are carried out,and the optimization schemes for image motion velocity matching and drift angle matching are formulated according the simulation results. Finally,this method is verified with a dynamic imaging experimental system. The results are indicative of that when image motion compensation for nadir-view camera is conducted using the proposed image motion velocity field model,the line pair of target images at Nyquist frequency is clear and distinguishable. Under the constraint that modulation transfer function( MTF) reduces by 5%,when the horizontal frequencies of the forward-view camera and the backward-view camera are adjusted uniformly according to the proposed image motion velocity matching scheme,the time delay integration( TDI) stages reach 6 at most. When the TDI stages are more than 6,the three groups of camera will independently undergo horizontal frequency adjustment. However, when the proposed drift angle matching scheme is adopted for uniform drift angle adjustment,the number of TDI stages will not exceed 81. The experimental results have demonstrated the validity and accuracy of the proposed image motion velocity field model and matching optimization scheme,providing reliable basis for on-orbit image motion compensation of aerospace mapping cameras.

Controllable Crack Propagation in Off-Axis Crushing of Stitched Composite Absorbers

Crack growth resistance plays a different role in crashworthiness analysis since the progressive energy absorption is based on controllable fracture mechanisms. In this regard, the present paper studies the efficient crack growth resistance in off-axis crushing of composite tubular structures by implementing natural fiber yarns. One of the through-to-thickness reinforcement methods known as stitching has been chosen to influence the axial and off-axis crushing process. Improving the crack growth resistance and appropriate fiber breakage at different stages of crushing process can significantly improve the resistance force and consequently the energy absorption capability of composite absorbers in axial and off-axis crushing. This analysis will be applied to non-stitched and stitched CFRP composite boxes which showed brittle fracture and transverse shearing crushing modes under off-axis loading of 10 degrees. The analytical methods are also implemented to analysze the effect of various failure mechanisms such as bending, friction, bundle fracture, and interlaminar crack growth for the observed crushing modes. The proposed model is able to predict the crushing load and crush force efficiency in close agreement from experimental studies.

Laminate Tailoring of Composite Tubular Structures to Improve Crashworthiness Design at Off-Axis Loading

This paper presents experimental and numerical investigation on the parameters effecting energy absorption capability of composite tubular structures at oblique loading to improve crashworthiness performance. Various inclined angles of 5°, 10°, 20° and 30° were selected for the study of off-axis loading. The results indicate that by increasing the lateral inclination angle the mean crushing force and also energy absorption capability of all tested sections decreased. From design perspective, it is necessary to investigate the parameters effecting this phenomenon. The off-axis loading effect that causes significant reduction in energy absorption was investigated and the effected parameters were improved to increase energy absorption capability. To establish this study, 10° off-axis loading was chosen to illustrate the obtained improvement in energy absorption capability. Five cases were studied with combinations of ply-orientation and flat trimming with 45° chamfer. This method was applied to the integrated 10° off-axis loading and the final results showed significant improvement in energy absorption capability of composite absorbers. Finite element model (FEM) was developed to simulate the crushing process of axial and off-axis composite section in LS-DYNA and the results were in good agreement with the experimental data.

Three-dimensional acoustic radiation force of a eukaryotic cell arbitrarily positioned in a Gaussian beam

Expressions are derived for calculating the three-dimensional acoustic radiation force(ARF)on a multilayer microsphere positioned arbitrarily in a Gaussian beam.A theoretical model of a three-layer microsphere with a cell membrane,cytoplasm,and nucleus is established to study how particle geometry and position affect the three-dimensional ARF,and its results agree well with finite-element numerical results.The microsphere can be moved relative to the beam axis by changing its structure and position in the beam,and the axial ARF increases with increasing outer-shell thickness and core size.This study offers a theoretical foundation for selecting suitable parameters for manipulating a three-layer microsphere in a Gaussian beam.

Simultaneous determination of polarization states and mode coefficients of fiber LP modes with four-channel off-axis holography

Four-channel off-axis holography is proposed to simultaneously understand the polarization states and the mode coefficients of linearly polarized (LP) modes in few-mode fiber. Far-field off-axis holograms in the four polarization directions ofthe fiber laser were acquired at the same moment through a four-channel holographic device. The weights, the relativephase differences, and the polarization parameters of the vector fiber laser mode can be solved simultaneously. The simulated and experimental mode analysis of the laser output by 1060-XP fiber with 6 LP modes at 632.8 nm is conducted, whichshows that the similarity of the total intensity distribution of the laser before and after mode analysis is above 0.97. Themode polarization states, the mode weights, and the relative phase differences of the few-mode laser can be determinedsimultaneously in a single shot by four-channel off-axis holography.

Vector bending sensor based on chirped long-period grating with off-axis micro-helix taper

Vector bending sensing has been consistently growing in many fields.A low-cost and high sensitivity vector bending sensor based on a chirped long-period fiber grating[LPFG]with an off-axis micro helix taper is proposed and experimentally demonstrated.The grating is composed of several sections of single-mode fiber with gradually larger lengths,and the off-axis micro helix tapers with fixed lengths when they are fabricated by using the arc discharge technology.The large refractive index modulation in the micro-helix taper greatly reduces the sensor size.The total length of the sensor is only 4.67 mm.The micro-helix taper-based LPFG can identify the bending direction due to the asymmetric structure introduced by the micro helix.The experimental results show that the transmission spectra of the sensor have distinct responses for different bending directions,and the maximum bending sensitivity is 14.08 nm/m^(-1)in the range from 0.128 m^(-1)to 1.28 m^(-1).The proposed bending sensor possesses pronounced advantages,such as high sensitivity,small size,low cost,and orientation identification,and offers a very promising method for bend measurement.

散乱点云的无垂直视差立体图像生成

散乱点云的立体显示能直观形象地还原被扫描物体。针对OpenGL未对Off-axis立体投影模型提供内建支持致使难以生成正负视差过渡平滑的立体图像,提出了一种Off-axis立体投影模型的OpenGL实现方法,依据双目成像原理与Off-axis模型推导投影矩阵,用以替换OpenGL中的投影矩阵,并利用OpenGL的四缓冲技术对散乱点云进行透视投影,从而生成符合深度感要求的无垂直视差立体图像,以便对散乱点云进行评估。实验证明,该方法能简单自然的实现无垂直视差的立体图像生成,且基于硬件加速渲染场景,能有效保证渲染速率,可广泛应用于对逼真度要求较高的立体显示环境。

“探测器级”单晶金刚石材料生长技术研究进展

为了获得高性能单晶金刚石探测器,综述了一种制备高质量单晶金刚石的方法。在制备过程中,尝试使用了Lift-off剥离技术,使衬底可重复利用,大大降低了金刚石材料的成本。研究表明,通过该方法制备的金刚石材料质量优于商用"电子器件级"金刚石;利用该类材料制作的金刚石探测器性能优异:对14 Me V中子和5.486 Me Vα粒子的能量分辨率分别达到1.5%和0.3%,电荷收集效率接近100%。

One-Dimensional Magnetic FeCoNi Alloy Toward Low-Frequency Electromagnetic Wave Absorption

Rational designing of one-dimensional(1D)magnetic alloy to facilitate electromagnetic(EM)wave attenuation capability in low-frequency(2-6 GHz)microwave absorption field is highly desired but remains a significant challenge.In this study,a composite EM wave absorber made of a FeCoNi medium-entropy alloy embedded in a 1D carbon matrix framework is rationally designed through an improved electrospinning method.The 1D-shaped FeCoNi alloy embedded composite demonstrates the high-density and continuous magnetic network using off-axis electronic holography technique,indicating the excellent magnetic loss ability under an external EM field.Then,the in-depth analysis shows that many factors,including 1D anisotropy and intrinsic physical features of the magnetic medium-entropy alloy,primarily contribute to the enhanced EM wave absorption performance.Therefore,the fabricated EM wave absorber shows an increasing effective absorption band of 1.3 GHz in the low-frequency electromagnetic field at an ultrathin thickness of 2 mm.Thus,this study opens up a new method for the design and preparation of high-performance 1D magnetic EM absorbers.

Ultrahigh Density of Atomic CoFe-Electron Synergy in Noncontinuous Carbon Matrix for Highly Efficient Magnetic Wave Adsorption

Improving the atom utilization of metals and clarifying the M–M’interaction is both greatly significant in assembling high-performance ultra-light electromagnetic wave-absorbing materials.Herein,a high-temperature explosion strategy has been successfully applied to assemble the hierarchical porous carbon sponge with Co–Fe decoration via the pyrolysis of the energetic metal organic framework.The as-constructed hybrid displays a superior reflection loss(RL)value of-57.7 d B and a specific RL value of-192 d B mg-1 mm-1 at 12.08 GHz with a layer thickness of 2.0 mm(loading of 15 wt%).The off-axis electron hologram characterizes the highly distributed numerous polarized nanodomain variable capacitors,demonstrating the dipole and interfacial polarization along the edges of the nanopores.More importantly,the X-ray absorption spectroscopy analysis verifies the mutual interaction between the metal cluster and carbon matrix and the electronic coupling responsible for the greatly improved electromagnetic wave absorption.

单向纤维复合材料的偏轴实验方法开发与评价(英文)

This study presents an integrated method suitable for off-axis tension and compression testing in unidirectional composites,and its application to the testing of in-plane shear characterization.A new rotating-grip test fixture,incorporating the attractive features of the existing pinned-end fixture and hydraulic wedge grips,has been developed.The proposed gripping system consists of two sets of jaw faces,each with a pair of self-aligning bearings that allows for loading in the axial and radial directions.Finite element analysis and experiments were performed to evaluate the effectiveness of the rotating-grip test fixture.Results from numerical calculations show that this method reduces stress concentrations near the end and produces relatively uniform stress distributions in the specimen gage section.Mechanical testing results show a considerable increase in the measured shear properties of composites,compared with the existing end grip systems.The results indicated that the new test fixture is significantly better than the conventional fixture,and is also comparable to the method of the oblique end-tab for off-axis testing.