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- 摘要
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[IEEE OCEANS 2018 MTS/IEEE Charleston - Charleston, SC, USA (2018.10.22-2018.10.25)] OCEANS 2018 MTS/IEEE Charleston - Dynamic beam shaping exploiting orbital angular momentum for underwater structured light illumination
摘要： This work demonstrates dynamic optical beam generation using two different approaches: a Mach-Zehnder interferometer to generate three coherently coupled orbital angular momentum modes and a HOBBIT (high-order Bessel beams integrated in time) system which switches between spatial modes. By expanding the number of coherently coupled modes, a broad range of structured light patterns can be spatially and temporally controlled for structured illumination in underwater imaging applications.
关键词： underwater,orbital angular momentum,interference,structured illumination,coherent
更新于2025-09-23 15:22:29
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Even-odd effect in higher-order holographic production of electron vortex beams with nontrivial radial structures
摘要： Structured electron beams carrying orbital angular momentum are currently of considerable interest, both from a fundamental point of view and for application in electron microscopy and spectroscopy. Until recently, most studies have focused on the azimuthal structure of electron vortex beams with well-defined orbital angular momentum. To unambiguously define real electron-beam states and realize them in the laboratory, the radial structure must also be specified. Here we use a specific set of orthonormal modes of electron (vortex) beams to describe both the radial and azimuthal structures of arbitrary electron wavefronts. The specific beam states are based on truncated Bessel beams localized within the lens aperture plane of an electron microscope. We show that their Fourier transform set of beams can be realized at the focal planes of the probe-forming lens using a binary computer-generated electron hologram. Using astigmatic transformation optics, we demonstrate that the azimuthal indices of the diffracted beams scale with the order of the diffraction through phase amplification. However, their radial indices remain the same as those of the encoding beams for all the odd diffraction orders or are reduced to the zeroth order for the even-order diffracted beams. This simple even-odd rule can also be explained in terms of the phase amplification of the radial profiles. We envisage that the orthonormal cylindrical basis set of states could lead to new possibilities in phase contrast electron microscopy and spectroscopy using structured electron beams.
关键词： truncated Bessel beams,astigmatic transformation,computer-generated hologram,electron vortex beams,orbital angular momentum,phase amplification
更新于2025-09-23 15:22:29
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Topological Space-Time Photonic Transitions in Angular-Momentum-Biased Metasurfaces
摘要： In this paper, topological space-time photonic transition of light in angular-momentum-biased metasurfaces is established, which yields a superposition of orbital-angular-momentum (OAM)-carrying beams at distinct frequency harmonics upon scattering whose topological charges and frequency shifts are correlated. A reflective dielectric metasurface is considered that consists of silicon nanodisk heterostructures integrated with indium-tin-oxide and gate dielectric layers placed on a back mirror forming a dual-gated field effect modulator. The metasurface is divided into several azimuthal sections wherein the nanodisk heterostructures are interconnected via biasing lines. Addressing each azimuthal section with radio-frequency biasing signals separately allows for flexible implementation of different spatiotemporal modulation profiles. Active tuning of OAM states with high mode-purity is demonstrated, which yields minimal cross-talk between OAM channels in a mode-multiplexed communication system. Moreover, the role of spatiotemporal modulation profile on the spectral and spatial diversity of OAM states is explored. It is shown that angular-momentum-biased metasurfaces allow opportunities for hybridized mode-division and wavelength-division multiple access through multiplexing and multicasting across distinct OAM states and wavelengths. The nonreciprocity of topological space-time photonic transitions across the temporal frequency domain and Hilbert space of OAM states is also investigated giving rise to distinct twisted light channels in up- and down-links.
关键词： orbital angular momentum,topological space-time photonic transitions,time-modulated metasurfaces,mode-multiplexing,wavelength-division multiplexing
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE 4th Advanced Information Technology, Electronic and Automation Control Conference (IAEAC) - Chengdu, China (2019.12.20-2019.12.22)] 2019 IEEE 4th Advanced Information Technology, Electronic and Automation Control Conference (IAEAC) - Research on Reliability of Active Distribution Network with Distributed Photovoltaic
摘要： In this paper, we demonstrate that the solid cylinder dielectric resonator antenna (CDRA) is a high radiation efficient device to generate orbital angular momentum (OAM) waves with different OAM modes at different frequencies. Theoretical formulations of its radiation fields are deduced in the cylindrical coordinate system, which shows that all components of the electric and magnetic fields have the azimuth dependence of ejm?. A full-wave simulation on a practical size CDRA is then implemented to validate the theoretical derivations. The simulation results show that different separated OAM modes can be obtained at different frequencies. Specifically, the higher order OAM modes are generated at higher electron magnetic modes, which makes CDRA a promising method to overcome the narrow band and multiband issues existing in the design of current OAM devices. Furthermore, a maximum radiation efficiency of 97.1% at 13.3 GHz, and a minimum radiation efficiency of 72.4% at 19.45 GHz are obtained in our simulation, which is a high radiation efficiency feature at the OAM resonant frequencies.
关键词： orbital angular momentum,high radiation efficient.,Cylinder dielectric resonator antenna
更新于2025-09-23 15:21:01
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Reducing orbital angular momentum crosstalk of the Bessel Gaussian beam for underwater optical communications
摘要： We derive the analytical expressions of the probabilities for the signal and the crosstalk orbital angular momentum (OAM) states of a high order Bessel Gaussian beam used in underwater optical communications. Our numerical results show that the probabilities of the signal and crosstalk OAM states are effected by the propagation distance and the parameters of the oceanic turbulence. The receiver aperture can be used to reduce the probabilities of the crosstalk OAM states and the probability of the detected signal OAM states keeps almost unchanged. Our results may improve the quality of the optical communications system.
关键词： Bessel Gaussian beam,orbital angular momentum,oceanic turbulence,underwater optical communications
更新于2025-09-23 15:21:01
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Gain of electron orbital angular momentum in a direct laser acceleration process
摘要： Three-dimensional “particle in cell” simulations show that a quasistatic magnetic ?eld can be generated in a plasma irradiated by a linearly polarized Laguerre-Gauss beam with a nonzero orbital angular momentum (OAM). Perturbative analysis of the electron dynamics in the low intensity limit and detailed numerical analysis predict a laser to electrons OAM transfer. Plasma electrons gain angular velocity thanks to the dephasing process induced by the combined action of the ponderomotive force and the laser induced–radial oscillation. Similar to the “direct laser acceleration,” where Gaussian laser beams transmit part of its axial momentum to electrons, Laguerre-Gaussian beams transfer a part of their orbital angular momentum to electrons through the dephasing process.
关键词： orbital angular momentum,electron dynamics,magnetic field generation,Laguerre-Gauss beam,plasma
更新于2025-09-23 15:21:01
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External pressure induced liquid crystal defects for optical vortex generation
摘要： Simple and arbitrary creation of liquid crystal (LC) defects can be highly useful, in particular, for the creation of optical vortex. We report a novel method to create an isolated and stable +1 type concentric LC defect by combing an external pressure on a vertically aligned liquid crystal cell (VALC) and the application of electric fields. The method does not require special material in alignment layer, nor patterned electrodes such as in spatial light modulator, but it can produce stable and rewritable defects in a LC cell. We show that the created +1 defect can be used to generate optical vortices with ±2(cid:125) orbital angular momentum. The simple and cost-effective process and its tunability for the position of defect make the method useful in various applications such as advanced optical communication and quantum computation using tunable optical vortices.
关键词： electric fields,orbital angular momentum,liquid crystal defects,optical vortex generation,external pressure
更新于2025-09-23 15:21:01
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Tunable topological charge vortex microlaser
摘要： The orbital angular momentum (OAM) intrinsically carried by vortex light beams holds a promise for multidimensional high-capacity data multiplexing, meeting the ever-increasing demands for information. Development of a dynamically tunable OAM light source is a critical step in the realization of OAM modulation and multiplexing. By harnessing the properties of total momentum conservation, spin-orbit interaction, and optical non-Hermitian symmetry breaking, we demonstrate an OAM-tunable vortex microlaser, providing chiral light states of variable topological charges at a single telecommunication wavelength. The scheme of the non–Hermitian-controlled chiral light emission at room temperature can be further scaled up for simultaneous multivortex emissions in a flexible manner. Our work provides a route for the development of the next generation of multidimensional OAM-spin-wavelength division multiplexing technology.
关键词： data multiplexing,orbital angular momentum,chiral light emission,non-Hermitian symmetry breaking,vortex light beams,spin-orbit interaction,microlaser,telecommunication wavelength
更新于2025-09-23 15:21:01
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First-principles theory of giant Rashba-like spin splitting in bulk GeTe
摘要： Large Rashba-like spin splitting has been recently found in the band structure of certain bulk ferroelectrics. In contrast to the relativistic Rashba effect, the chiral spin texture and large spin splitting of the electronic bands depend strongly on the character of the band and atomic spin-orbit coupling. We establish that this can be traced back to an interplay between the orbital angular momentum and ferroelectricity. The additional dependence on the orbital composition of the bands is crucial to the complete picture of the effect. Results from ?rst-principles calculations on ferroelectic GeTe verify the key predictions of the model.
关键词： Rashba-like spin splitting,orbital angular momentum,ferroelectricity,spin-orbit coupling,GeTe
更新于2025-09-23 15:21:01
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Multispectral Management of the Photon Orbital Angular Momentum
摘要： We report on a programmable liquid crystal spatial light modulator enabling independent orbital angular momentum state control on multiple spectral channels. This is done by using electrically controllable “topological pixels" that independently behave as geometric phase micro-optical elements relying on self-engineered liquid crystal defects. These results open interesting opportunities in optical manipulation, sensing, imaging, and communications, as well as information processing. In particular, spectral vortex modulation allows considering singular spatiotemporal shaping of ultrashort pulses which may find applications in many areas such as material processing, spectroscopy, or elementary particles acceleration.
关键词： liquid crystal spatial light modulator,spectral vortex modulation,photon orbital angular momentum,geometric phase micro-optical elements,ultrashort pulses
更新于2025-09-23 15:21:01