- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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Electron holography for vortex beams
摘要： A combined technology of vortex beam technique and electron holography has been developed. A range of about 10 times the diameter of the grating opening was irradiated and electron holography, electron vortex beam, orbital angular momentum, helical wavefront, wave propagation two-wave interference between a Bragg diffraction wave as a vortex beam and transmitted wave from and around a fork-shaped grating was recorded as a hologram. Reconstruction by using the Fourier transform method has been simultaneously performed for amplitude and phase distributions. Furthermore, by using a wave aberration function, amplitude and phase distributions at various propagation positions were reconstructed numerically, resulting in confirmation of vortex beam twists.
关键词： helical wavefront,electron holography,electron vortex beam,orbital angular momentum,wave propagation
更新于2025-09-19 17:13:59
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Structured Light from Lasers
摘要： Structured light is derived from the ability to tailor light, usually referring to the spatial control of its amplitude, phase, and polarization. Although a venerable topic that dates back to the very first laser designs, structuring light at the source has seen an explosion in activity over the past decade, fuelled by a modern toolkit that exploits the versatility of diffractive structures, liquid crystals, metasurfaces/metamaterials, and exotic laser geometries, as well as a myriad of applications that range from imaging, microscopy, and laser material processing to optical communication. Here, the recent progress in creating and controlling structured light is reviewed, with particular emphasis on structuring light at the source: structured light lasers. The various design approaches, including pump shaping, cavity geometries, and the use of custom intracavity optical elements, implemented in a variety of lasers from microchip solutions to high-power fibers are covered in a tutorial style. The history and latest developments in the field are reviewed, elucidating the various structured light patterns that have been created from lasers, including orbital angular momentum and vector states of light. Finally, the present challenges and limitations are highlighted, along with comments on likely future trends.
关键词： optical modes,random lasers,topological lasers,orbital angular momentum,vector beams,structured light
更新于2025-09-19 17:13:59
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Hybrid Entangled States With Multi-Degree of Freedom and High Purity for Internet of Vehicles
摘要： The development of intelligent Internet of vehicles (IoV) is based on communication technology, especially the quantum communication of hybrid entangled states based on orbital angular momentum (OAM). The quantum key distribution (QKD) method is demonstrated using hybrid entangled states with multi-degree of freedom and high purity based on OAM. First, the polarization entangled photon pairs are produced by two type I BBO crystals by means of spontaneous parametric down-conversion (SPDC). The polarization-OAM hybrid entangled states are created by q-plate (QP) to realize QKD. It is found that the polarization entangled photon pairs have the characteristics of OAM. A single mode fiber (SMF) is proposed to filter the topological charge non-zero photons and purify the polarization entangled photon pairs. Then the purification setup with M-Z interferometer and beam rotator (BR) is presented which can purify the polarization-OAM hybrid entangled states. The high purity polarization-OAM hybrid entangled states are implemented, and the QP conversion rate of 3 secondary feedbacks is 99.84% theoretically. Analysis indicates that precise purity polarization-OAM hybrid entangled state can increase the fidelity of information and improve the anti-interference ability in this program without mutually unbiased bases (MUBs). The photon utilization rate, energy-efficient and low-latency communication can be greatly improved by using the OAM carrying information.
关键词： hybrid entanglement,orbital angular momentum (OAM),coincidence measurement,high purity,Internet of vehicles (IoV),low-latency
更新于2025-09-19 17:13:59
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Photonic Spin-Multiplexing Metasurface for Switchable Spiral Phase Contrast Imaging
摘要： As the two most representative operation modes in an imaging system, bright-field imaging and phase contrast optical imaging can extract different morphological information on an object. Developing a miniature and low-cost system capable of switching between these two imaging modes is thus very attractive for a number of applications, such as biomedical imaging. Here, we propose and demonstrate that a Fourier transform setup incorporating an all-dielectric metasurface can perform a two-dimensional spatial differentiation operation and thus achieve isotropic edge detection. In addition, the metasurface can provide two spin-dependent, uncorrelated phase profiles across the entire visible spectrum. Therefore, based on the spin-state of incident light, the system can be used for either diffraction-limited bright-field imaging or isotropic edge-enhanced phase contrast imaging. Combined with the advantages of planar architecture and ultrathin thickness of the metasurface, we envision this approach may open new vistas in the very interdisciplinary field of imaging and microscopy.
关键词： phase contrast imaging,edge detection,orbital angular momentum,Metasurface
更新于2025-09-19 17:13:59
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Design of a low-dispersion ring-core photonic crystal fiber supporting 26 OAM modes
摘要： We propose a new photonic crystal fiber structure to support 26 orbital angular momentum (OAM) modes from 1.25μm to 1.95μm. It has been proven that this fiber has good performance by the numerical analysis, such as low confinement loss, and relatively flat chromatic dispersion. The fiber has only two-layer of air holes, which makes it easier to be manufactured. What’s more, the fiber has a more stable physical structure, the triangular arrangement of air holes which can guarantee the air holes hardly deforms.
关键词： ring-core photonic crystal fiber,orbital angular momentum
更新于2025-09-16 10:30:52
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Generation of vortex waves in non-coaxial cylindrical waveguides
摘要： A non-coaxial waveguide composed of a cylindrical resonator of radius R and cylindrical waveguides with the radii r1 and r2, respectively, is considered. The radii satisfy the inequality r1 < r2 < R. The conversion from the channel with zero orbital angular momentum (OAM) into the channels with non-zero OAM is achieved by shifting the center lines of the waveguides relative to the center line of the cylindrical resonator. The center lines of input and output waveguides are shifted relative to each other by the angle D/ in order to twist the output acoustic wave. The conversion ef?ciency of the input wave with zero OAM into the output wave with non-zero OAM as dependent on the frequency, length of the resonator, and D/ is considered, and the domains where the ef?ciency can reach almost 100% are found.
关键词： non-coaxial cylindrical waveguides,acoustic resonator,orbital angular momentum,vortex waves
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Inverse Design of Orbital Angular Momentum Mode Demultiplexer by Combining Wavefront Matching Method and Gradient Descent Algorithm
摘要： The spatial mode demultiplexer is a critical component in the mode division multiplexing communication system, which requires the merits of power-efficiency and low-crosstalk. It has been demonstrated that any unitary transform of spatial modes can be implemented by passing through a succession of phase masks with free-space propagation in between, and the key is to inversely design the phase distribution of each phase mask. One inverse approach is based on wavefront matching method, which is employed in the technique termed multi-plane light conversion (MPLC). This approach enables an efficient optimization of overlap integrals between the obtained modes and the desired modes. However, this method does not have an objective function, meaning that it is incapable of implementing specific optimization. Another approach is based on the gradient descent algorithm, which is flexible in choosing objective functions, while the performance in maximizing overlap integrals is less desirable when compared with wavefront matching method. In this work, we design an efficient orbital angular momentum (OAM) demultiplexer inversely by combining the wavefront matching method and the gradient descent algorithm. Firstly, we employ the wavefront matching method to optimize all the phase masks until convergence. Then, by setting adjacent crosstalk as a part of the objective function, we apply the gradient descent algorithm to further optimize the mode demultiplexing performance. Since the objective function is already close to the local minimum, the subsequent gradient descent process will converge in a few iterations. To confirm this idea, we demonstrate the mode transformation from OAM modes with azimuthal topological charge from l = -3 to l = 3 to displaced Gaussian modes. The configuration including the input and output modes as well as the number and positions of the phase masks are determined with reference to the spiral transformation scheme. By the combinational use of aforementioned methods, we design an OAM demultiplexer that can sort 7 pure vortex modes with 3 phase masks. The designed phase profiles present a similarity to those implemented in spiral transformation, especially for the third phase mask resembling to an elliptical lens. The maximum insertion loss and crosstalk of the device are -0.2 dB and -21.1 dB, with a 5.6-dB improvement in maximum crosstalk resulting from the further gradient descent optimization after wavefront matching.
关键词： Gradient Descent Algorithm,Mode Demultiplexer,Inverse Design,Wavefront Matching Method,Orbital Angular Momentum
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Spiral Bandwidth of Four-Wave Mixing in Rubidium Vapour
摘要： Atomic vapours are an experimentally simple and ef?cient system in which to study nonlinear wave mixing. We study a four-wave mixing (FWM) process in rubidium vapour which ef?ciently converts 780 and 776 nm light to 420 nm and 5.2 μm ?elds [1]. In particular, we quantitatively investigate the transfer of orbital angular momentum (OAM) between the FWM ?elds. OAM, and structured light more generally, is an important research tool for optical manipulation, imaging and communication. Phase-matched nonlinear processes are both longitudinally and transversely phase coherent, and therefore OAM, which is associated with spiral phase fronts, must be conserved between the pump and generated ?elds [2]. This makes wave mixing an ideal tool for frequency conversion and generation of a variety of OAM states for use in both classical and quantum communication [3]. In our FWM process, conservation of OAM determines the total OAM carried by the 420 nm and 5.2 μm ?elds - but not how it is distributed between them. Fig. 1 (a) shows the intensity pro?le and interferogram (formed by interfering the beam with its mirror image) of the 420 nm ?eld when the pump beams each carry (cid:2)ˉh of OAM ((cid:2) = (cid:2)780 = (cid:2)776). We perform quantitative analysis of each interferogram to obtain the full Laguerre-Gauss mode decomposition of the 420 nm ?eld (Fig. 1 (b)). For small values of pump OAM, the 420 nm light is generated predominantly in one mode [4], but as the pump OAM increases the OAM spectrum broadens [5]. In order for OAM to be conserved, this indicates that the 420 nm and 5.2 μm light is generated in an OAM-entangled state. From the 420 nm mode decomposition we infer the spiral bandwidth (a measure of the number of entangled modes), Δ(cid:2)B, as well as the entanglement entropy, S, of this state. Both the experimental and theoretical results show that the generated state is strongly pump mode-dependent, with the spiral bandwidth increasing with increasing pump OAM. These results indicate that this system is likely to be an ef?cient source of OAM-entangled photon pairs with widely-disparate wavelengths.
关键词： entanglement entropy,orbital angular momentum,four-wave mixing,rubidium vapour,spiral bandwidth
更新于2025-09-16 10:30:52
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Modeling and Optimization of Vortex Modes Propagation in Rectangular Dielectric Waveguides
摘要： We study analytically and numerically the possibility of vortex modes propagation over planar dielectric rectangular waveguides, and consider the problem of waveguide geometry optimization for the support of vortex modes. The results show, that theoretically rectangular waveguides can provide transmission of quasi-TE and quasi-TM modes with high purity states of orbital angular momentum (OAM) in the dominant ?eld component. However, only for the quasi-generate mode of azimuthal order ±1 the constituent eigenmodes can propagate in a phase-matched regime, and the vortex modes of higher azimuthal orders can propagate only with a certain beat length. Moreover, as the target azimuthal order increases, the normalized power of the corresponding OAM state in the modal superposition decreases. The analytical predictions have been veri?ed by numerical electromagnetic simulations of silicon nitride waveguides providing ?eld distributions and OAM spectra of the corresponding modal superpositions.
关键词： integrated photonics,silicon nitride,optical waveguides,Optical orbital angular momentum (OAM)
更新于2025-09-16 10:30:52
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Stable generation of orbital angular momentum mode with an all-fiber laser
摘要： In this paper, an all-fiber laser that can generate stable OAM modes with topological charges of ±1 is demonstrated. A ring-core fiber designed in-house is used to reduce the crosstalk between OAM mode and other modes. A ring-core fiber-based long-period fiber grating (LPFG) and a fiber Bragg grating (FBG) are employed to select desired OAM mode. The coupling ratio of LPFG from HE11 mode to OAM mode exceeds 16 dB, and the mode purity of ±1 is demonstrated. The purity of OAM mode is as high as 94.41%. This simple and compact fiber laser can be integrated into fiber-based OAM mode multiplexing optical communication system.
关键词： orbital angular momentum,fiber Bragg grating,ring-core fiber,long-period fiber grating,all-fiber laser
更新于2025-09-16 10:30:52