Monoenergetic ion beam generation by driving ion solitary waves with circularly polarized laser light

Experimental data from the Trident Laser facility is presented showing quasimonoenergetic carbon ions from nm-scaled foil targets with an energy spread of as low as ±15% at 35?MeV. These results and high-resolution kinetic simulations show laser acceleration of quasimonoenergetic ion beams by the generation of ion solitons with circularly polarized laser pulses (500?fs, λ=1054 nm). The conversion efficiency into monoenergetic ions is increased by an order of magnitude compared with previous experimental results, representing an important step towards applications such as ion fast ignition.     

Nuclear orientation by anisotropic collisions

The anisotropic interaction of fast ions with atoms or a solid results in an orientation of the spatial distribution of the orbital angular momenta of excited electronic levels. This orientation of the electronic shell is transfered via hyperfine (hf) interaction to the nuclei and a vector polarization of the nuclear spins is observed. Since this kind of fast beam interaction generates an anisotropy in a rather general way, this technique seems to provide a universal source for polarized ions. General concepts of this type of interaction are discussed, and the applications to produce nuclear spin polarized ions and future developments in this field are outlined.     

Novel MRI applications of laser-polarized noble gases

Gas-phase nuclear magnetic resonance (NMR) has great potential as a probe for a variety of interesting physical and biomedical problems that are not amenable to study by water or similar liquid. However, NMR of gases was largely neglected due to the low signal obtained from the thermally polarized gases with very low sample density. The advent of optical pumping techniques for enhancing the polarization of the noble gases³He and¹²⁹Xe has bought new life to this field, especially in medical imaging where³He lung inhalation imaging is approaching a clinical application. However, there are numerous applications in materials science that also benefit from the use of these gases. We review primarily nonmedical applications of laser-polarized noble gases for both NMR imaging and spectroscopy and highlight progress with examples from our laboratory including high-resolution imaging at millitesla applied field strength and velocity imaging of convective flow. Porous media microstucture has been probed with both thermal and laser-polarized xenon, as xenon is an ideal probe due to low surface interaction with the grains of the porous media.     

Linear polarization Yb<Superscript>3+</Superscript>-doped fiber laser with novel innerclad structures

Results on high radiance Yb³⁺-doped fiber lasers with novel double innerclad structures (double-D clad and four hole) and polarized output at ≈1090 nm are presented. We have demonstrated >40% of the total output power being polarized, making the fiber laser suitable for LIDAR and second-harmonic generation (SHG) applications. It also showed a 10-nm tuning range with low (less than 10 mW) average power variations. The narrow linewidth source was pumped with a low cost, low brightness laser diode, and exhibited a relatively low slope efficiency, which gives room for improvement by using a 976-nm pump source where Yb³⁺ has a narrower linewidth and at least five times higher absorption.     

Changes in statistics of the instantaneous Stokes parameters of a quasi-monochromatic electromagnetic beam on propagation

The changes in the probability density functions (PDFs) are discussed, of the instantaneous Stokes parameters of a quasi-monochromatic electromagnetic beam propagating in free space. Such changes may be caused by correlations between the components of the electric field at a pair of points in the source plane. When the fluctuations of the electric field are governed by Gaussian statistics the PDFs of the instantaneous Stokes parameters at any distance from the source are completely determined by the two-point correlation properties of the field in the source plane. These results can be used for synthesis of sources generating random beams with prescribed statistical properties. They also may find applications in remote sensing, tomography and communications with partially coherent and partially polarized light.     

Generation of radially polarized beams using spatial light modulator

Radially polarized beams have attracted much attention and found many applications in many optical systems, recently. And generation of radially polarized beams is necessary for experimental research and applications. In this paper, a kind of generation method was proposed. Two beams are obtained by spatial light modulator and pi phase plate, and then interfere to form desirable radially polarized beams. Experimental results show that radially polarized beams are higher property, which shows this kind of interferential generation of radially polarized laser beams work effectively.     

Some Applications of a 57Co Monochromatic Circularly Polarized Source

A recently constructed monochromatic, circularly polarized Mössbauer source was used for the determination of the magnetic texture. The advantages of the polarized source are demonstrated by showing that in a particular recording material the magnetic moments are inclined from an original direction of magnetization, tending to align in the plane and along the axis of the tape.     

Manipulating Nonlinear Photocurrent from Interlayer Coupling in Bilayer Metamaterials for Polarized Terahertz Generation

Polarized terahertz (THz) wave generation is of great significance for chiral and anisotropic sensing applications. However, how to manipulate amplitude, polarization, and ellipticity of the THz generation is still a fundamental challenge. Herein, polarized THz wave generation is achieved from a bilayer metamaterial consisting of T-shaped structure (TSS) and split resonator rings (SRRs) by combining Maxwell and hydrodynamic equations. The elliptically polarized THz wave can be synthetized directly from horizontally and vertically polarized THz components due to the orthogonal nonlinear photocurrents along the arm-directions of TSS and SRRs, respectively. Besides, the ellipticity and the orientation angle of the THz polarization ellipse can be modulated by the twist angle between the SRRs and TSS layers. The maximum ellipticity can reach 0.34 while the orientation angle is tunable from −0.45 to 0.48π by tuning the twist angle. This work proposes an interlayer coupling method for the polarized THz sources based on metamaterials in potential circular dichroism and chiral sensing applications.     

Probing time delay of strong-field resonant above-threshold ionization

The high-resolution three-dimensional photoelectron momentum distributions via above-threshold ionization(ATI)of Xe atoms are measured in an intense near circularly polarized laser field using velocity map imaging and tomography reconstruction. Compared to the linearly polarized laser field, the employed near circularly polarized laser field imposes a more strict selection rule for the transition via resonant excitation, and therefore we can selectively enhance the resonant ATI through certain atomic Rydberg states. Our results show the self-reference ionization delay, which is determined from the difference between the measured streaking angles for nonadiabatic ATI via the 4 f and 5 f Rydberg states, is 45.6 as. Our method provides an accessible route to highlight the role of resonant transition between selected states, which will pave the way for fully understanding the ionization dynamics toward manipulating electron motion as well as reaction in an ultrafast time scale.     

能量连续可调LCS光源SINAP-III

X/γ探测器在航天等国家战略需求领域具有非常广泛和重要的应用。 然而, X/γ探测器要在其有效能区进行精确的标定后才能发挥作用。 目前我国缺乏sub MeV～MeV能量连续可调、 单色性好的γ源, 而用于航天的X/γ探测器无法完成精确定标, 从而使航天探测的发展出现瓶颈问题。 提出了升级原有的激光康普顿散射(LCS)原理性实验装置的方案, 建立了一个通过改变激光入射角来连续调节散射光子能量、 准单色、 极化、 sub MeV～MeV LCS光源(SINAP-III), 从而开拓LCS光源在我国航天领域（如用于航天的X/γ探测器能量定标和抗辐射加固评估研究）的崭新应用前景, 并为将来建设一个基础和应用研究相结合的多功能的γ源实验平台打下基础。 The X/γ detectors in the field of national stratagem, such as astronautical technology, have very broad and important application. These detectors, however, will play their role properly only after accurate calibrations in effective energy region. For the shortage of continuously adjustable and quasi monochromatic γ source in China, it is impossible for the detector employed in aerospace to achieve an accurate calibration so that development of such detector has encountered a big obstacle (or a bottleneck). Therefore, we propose to upgrade the original LCS device to an adjustable photon energy by changing incident angle of laser beam, monochromatic, and polarized sub MeV~MeV LCS γ source(SIMAP III) , in order to explore the new applications of LCS γ source in aerospace as well as to establish a platform for a multifunctional of γ source.     

Production of polarized molecules of hydrogen isotopes

The possibility of producing polarized molecules of hydrogen isotopes by their spin separation in the inhomogeneous field of superconducting magnets has been demonstrated. This method proposed in our previous works has been implemented with a source of polarized atoms developed at the Budker Institute for Nuclear Physics. The measured flux of polarized molecules is compared with the simulation results. The possibility of developing a more intense source of polarized molecules is discussed.     

Experimental verification of focus tailoring using circularly polarized vortex beams with annular pupil mask

The focusing properties of circularly polarized vortex beam are experimentally verified by examining two-photon fluorescent emission patterns inside an fluorescent microsphere. Very good agreements between the experimental and theoretical results have been obtained. Annular pupil masks are used to tailor the profile at the focus. When an circularly polarized beam with the appropriate handedness is used in combination with an annular pupil aperture, a strong longitudinal component is observed, which results in a raised center and a smaller focal spot. This interesting focusing property can be utilized in applications that require a distinct longitudinal component.     

Circularly polarized localized near-field radiation at the nanoscale

Diffraction-limited circularly polarized electromagnetic radiation has been widely used in the literature for various applications at both optical and microwave frequencies. With advances in nanotechnology, emerging plasmonic nano-optical applications, such as all-optical magnetic recording, require circularly polarized electromagnetic radiation beyond the diffraction limit. In this study, a plasmonic cross-dipole nano-antenna is investigated to obtain a circularly polarized near-field optical spot with a size smaller than the diffraction limit of light. A cross-dipole nano-antenna is composed of four metallic nano-rods placed at a perpendicular orientation with respect to each other. The performance of the nano-antenna is investigated through numerical simulations. In the first part of this study, the nano-antenna is illuminated with a diffraction-limited circularly polarized radiation. An optimal antenna geometry is specified to obtain an intense optical spot that satisfies two necessary conditions for circular polarization: a phase difference of 90° and a unit amplitude ratio between the electric field components in the vicinity of the antenna gap. In the second part of this study, the nano-antenna is illuminated with diffraction-limited linearly polarized radiation. It is shown that the phase difference between the electric field components can be adjusted by selecting either different antenna lengths or different gap distances in the vertical and horizontal directions. Due to the relatively short wavelength of surface plasma waves on the antenna, it is demonstrated that the phase difference can be sufficient to obtain circularly polarized light. An optimal physical configuration for the nano-antenna and the polarization angle of the incident light is identified to obtain a circularly polarized optical spot beyond the diffraction limit from diffraction-limited linearly polarized radiation.     

Carbon Quantum Dot Optical Properties for potential infiltration into Hollow Core Photonic Crystal Fibers

Carbon quantum dots (CQD) have received significant attention in recent years due to their potential applications in optics and sensing. In this study, the authors report on the first characterization of the optical activity and broad absorption spectrum covering from short-wave ultraviolet, at 200 nm, to mid-infrared, at 1600 nm, of CQD synthesized using the “low-molecular-weight alcohols electrochemical carbonization” method. The CQD are analyzed using spectroscopic techniques, optical activity in the infrared, and high-resolution transmission electron microscopy. Results show a CQD size distribution of 5±3 nm and spherical morphology. The absorption spectra show increased absorption at both, high and low frequency. Additionally, the specific rotation of the CQD solution is significantly higher than that of pure ethanol, by three orders of magnitude. These findings suggest that CQD may have potential applications in polarized infrared filters and/or sensors due to their ability to rotate the polarization state of light at 1550 nm. The results of this study provide valuable insights into the optical properties of CQD and their potential for infiltration into hollow core photonic crystal fibers, making them a promising material for future research and development in the field of optics and sensing.     

光阴极电子枪微波与激光同步系统研究

光阴极微波电子枪中,微波与激光脉冲的同步问题是其能否稳定工作的关键之一.我们自行设计、采用了一种取样锁相电路,用频率不很稳定的激光脉冲的基波与S波段高频微波直接取样鉴相,提高了锁相精度,实现了超快激光脉冲与高频微波的精准同步,这在国内还是第一次.均方根时间抖动为0.57ps,时间抖动的最大值为2.6ps,锁相精度完全满足SDUV项目光阴极微波电子枪的要求.     

Angular distribution of photoelectrons at 584 Å using polarized radiation

Photoelectron angular distributions for Ar, Xe, N₂, O₂, CO, CO₂, and NH₃ have been obtained at 584 Å by observing the photoelectrons at a fixed angle and simply rotating the plane of polarization of a highly polarized photon source. The radiation from a helium DC glow discharge source was polarized (84%) using a reflection type polarizer.     

Status of the polarized ions source for the JINR accelerator complex

The project assumes the design and construction of a universal high-intensity source of polarized deuterons (protons) using a charge-exchange plasma ionizer. The output D ⁺↑ (H ⁺↑) current of the source is expected to be at a level of 10 mA. The polarization will be up to 90% of the maximal vector (±1) for D ⁺↑ (H ⁺↑) and tensor (+1, ?2) for D ⁺↑ polarization. Realization of the project is carried out in close cooperation with INR of the RAS (Moscow). The equipment available from the CIPIOS ion source (IUCF, Bloomington, USA) is partially used for the Dubna setup. The new source at the JINR Nuclotron accelerator facility will make it possible to increase the polarized deuteron beam intensity up to the level of 10¹⁰ d/pulse. The first results of the source of polarized atoms testing are presented.     

一种分焦平面偏振成像系统光源标定方法北大核心CSCD

水下偏振成像技术是目前水下成像研究的热点,由于自然光在水中衰减大,水下成像系统多采用主动照明方式。针对分焦平面偏振成像系统中偏振照明光源与偏振探测像元偏振方向不匹配引起采集图像偏振信息存在的偏差,进而影响目标图像增强质量的问题,提出了一种分焦平面偏振成像系统光源标定方法。阐述了偏振光源的标定原理,然后给出偏振光源标定的实施步骤,最后采用偏振去雾算法和图像质量评价方法对标定前后的水下目标图像进行了图像增强和图像质量评价。评价结果表明,标定后的增强图像质量优于未标定的增强图像质量,平均梯度最大提升了2.48倍。该标定方法简单有效,实用性强,适用于分焦平面偏振成像系统偏振光源标定。     

真实海洋表面的太阳耀光偏振辐射特性仿真与分析

由于镜面反射的原因,海洋表面呈现反射强烈的太阳耀光.水体本身属于低反射率的暗目标,太阳耀光成为水体航空航天遥感图像中的噪声;太阳耀光具有强偏振的特点,经过计算可以作为评价在轨传感器偏振指标的替代定标标准光源;也可以用来计算气体成分或者反演气溶胶参数.无论是去除噪声还是获取标准光源,都需要精确计算其辐射特性物理参数.文章...     

Focusing of radially polarized beam with radial cosine phase wavefront

Radially polarized beam has gained much interest recently due to its properties and applications. In this article, the focusing properties of radially polarized beam with radial cosine phase wavefront are investigated theoretically. Results show that when the radially polarized beam with radial cosine wavefront phase is focused, the focal pattern differs considerably with frequency parameter in the cosine function term. In the high numerical aperture focusing system, focal shift occurs, and novel focal patterns evolve considerably, for instance, from only one peak to two or multiple overlapping peaks. In addition, peak intensity ratio of radially polarized component to longitudinal polarized component in the focal region fluctuates smoothly for low-frequency parameter, then drops sharply, and comes back remarkably with increasing frequency parameter. Simultaneously focal shift increases slowly, and then decreases, suddenly, focal shift sign changes that results from focal switch phenomenon, and then fluctuates.