- 标题
- 摘要
- 关键词
- 实验方案
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Numerical study of orbital angular momentum-entanglement in turbulence with adaptive optics system compensation
摘要： While the entangled orbital angular momentum (OAM) photons propagate through the turbulent atmosphere, the OAM entanglement is decoherent. Adaptive optics (AO) system is an effective technique to mitigate wavefront distortion induced by atmospheric turbulence. In this paper, we investigate the performance of the system when the entangled OAM photons propagate though atmospheric turbulence with AO system compensation. The influence of reconstruction algorithm and spatial bandwidth of corrector is analyzed. The results show that branch-point (BP) algorithm has better compensation performance when Rytov number > 0.2 than the least mean square error (LS) algorithm. High spatial bandwidth has better compensation performance.
关键词： turbulence,orbital angular momentum,compensation,adaptive optics,entanglement
更新于2025-09-10 09:29:36
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[Springer Tracts in Modern Physics] Parity-time Symmetry and Its Applications Volume 280 || PT-Symmetry on-a-Chip: Harnessing Optical Loss for Novel Integrated Photonic Functionality
摘要： The development of non-Hermitian parity-time (PT) symmetric quantum mechanics has offered a powerful platform to engineer novel device functionality for integrated photonics. In this chapter, we review the chip-scale applications of PT-symmetry in photonic devices, including the implementation of the unidirectional reflectionless PT metamaterial, coherent asymmetric light-light switching, and orbital angular momentum (OAM) laser on-chip. We study the optical analogy of non-Hermitian PT systems, manipulate the complex refractive index properties such as gain/loss modulation, and investigate the unique wave transport characteristics near the exceptional point (EP) to achieve these intriguing on-chip functionalities.
关键词： light-light switching,orbital angular momentum laser,optical loss,non-Hermitian quantum mechanics,integrated photonics,PT-symmetry,unidirectional reflectionless,exceptional point
更新于2025-09-10 09:29:36
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All-optical generation and ultrafast tuning of non-linear spin Hall current
摘要： Spin Hall effect, one of the cornerstones in spintronics refers to the emergence of an imbalance in the spin density transverse to a charge flow in a sample under voltage bias. This study points to a novel way for an ultrafast generation and tuning of a unidirectional nonlinear spin Hall current by means of subpicosecond laser pulses of optical vortices. When interacting with matter, the optical orbital angular momentum (OAM) carried by the vortex and quantified by its topological charge is transferred to the charge carriers. The residual spin-orbital coupling in the sample together with confinement effects allow exploiting the absorbed optical OAM for spatio-temporally controlling the spin channels. Both the non-linear spin Hall current and the dynamical spin Hall angle increase for a higher optical topological charge. The reason is the transfer of a higher amount of OAM and the enhancement of the effective spin-orbit interaction strength. No bias voltage is needed. We demonstrate that the spin Hall current can be all-optically generated in an open circuit geometry for ring-structured samples. These results follow from a full-fledged propagation of the spin-dependent quantum dynamics on a time-space grid coupled to the phononic environment. The findings point to a versatile and controllable tool for the ultrafast generation of spin accumulations with a variety of applications such as a source for ultrafast spin transfer torque and charge and spin current pulse emitter.
关键词： optical vortices,orbital angular momentum,Spin Hall effect,quantum rings,spin-orbit interaction,spintronics
更新于2025-09-10 09:29:36
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Unified treatment of the total angular momentum of single photons via generalized quantum observables
摘要： In this paper, we provide a consistent framework to address the notorious difficult decomposition of the single-photon total angular momentum (TAM) into a spin (SAM) and an orbital (OAM) component. We discuss the canonical decomposition into SAM and OAM components, which are the generators of internal and spatial rotations in the space of physical states. We find that those operators are mutually compatible but unsharp quantum observables, therefore POVM (Positive Operator-Valued Measures) describe their joint measurements. We present another decomposition of the TAM, which we denote as a non-canonical one. The operators resulting from this decomposition are mutually incompatible but sharp quantum observables, thus PVM (Projector-Valued Measurements). This fact reflects their consistency with the transversality condition of single-photon wavefunctions, thus explains the underlying physics from a quantum information theoretic view. Furthermore, we discuss the implementations on joint measurements for both decompositions and provide an explicit calculation of all these quantities for circularly polarized Gaussian single-photon states. The difference between the canonical and non-canonical momenta leads to observable differences in higher-order statistical moments.
关键词： spin angular momentum,total angular momentum,quantum observables,orbital angular momentum,PVM,single photons,POVM
更新于2025-09-09 09:28:46
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - A Novel Imaging Formation of Electromagnetic Vortex Sar with Time-Variant Orbital-Angular-Momentum
摘要： In recent years, electromagnetic vortex waves carrying orbital angular momentum (OAM) arouse extensive attention in remote sensing imaging fields. However, most of the researches concentrate on the staring imaging mode, where the radar is motionless relative to the targets. We establish a novel system operation mode based on the principle of synthetic aperture radar (SAR). The echo model upon this novel operation mode is established and the new imaging method modified from the back-projection (BP) algorithm is deduced. Simulation and image evaluation results demonstrate the validation of the proposed method and OAM-based SAR system can be utilized in the SAR data acquisition and signal processing fields.
关键词： Orbital angular momentum (OAM),back-projection (BP) algorithm,synthetic aperture radar (SAR),electromagnetic (EM) vortex
更新于2025-09-09 09:28:46
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Vortex instability in turbulent free-space propagation
摘要： The spatial structuring of optical fields is integral within many next generation optical metrology and communication techniques. A verifiable physical model of the propagation of these optical fields in a turbulent environment is important for developing effective mitigation techniques for the modal degradation that occurs in a free-space link. We present a method to simulate this modal degradation that agrees with recently reported experimental findings. A 1.5 km free-space link is emulated by decomposing the optical turbulence that accumulates over a long distance link, into many, weakly perturbing steps of 10 m. This simulation shows that the high-order vortex at the centre of the helical phase profiles in modes that carry orbital angular momentum of ? are unstable and fracture into many vortices when they propagate over the link. This splitting presents issues for the application of turbulence mitigation techniques. The usefulness of pre-correction, post-correction, and complex field conjugation techniques are discussed.
关键词： optical propagation,orbital angular momentum,adaptive optics,optical vortices,atmospheric turbulence
更新于2025-09-09 09:28:46
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[OSA CLEO: Science and Innovations - San Jose, California (2015..-..)] CLEO: 2015 - Demonstration of Distance Emulation for an Orbital-Angular-Momentum Beam
摘要： We design and experimentally demonstrate a free-space distance emulator for propagating OAM beams over long distances in a lab environment. The performance of the system is assessed by measuring spot radius and radius of curvature of propagated beams.
关键词： OAM beams,Orbital-angular-momentum,free-space emulator,Laguerre Gaussian beams
更新于2025-09-09 09:28:46
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Various angle periods of parabolic coincidence fringes in violation of the Bell inequality with high-dimensional two-photon entanglement
摘要： Two quantum states of two half-charge optical vortexes with relative azimuthal angle π are orthogonal, by which two half-charge spiral phase plates with intersection angle π can be used to demonstrate a parabolic coincident fringe in the Bell inequality experiment with high-dimensional two-photon orbital angular momentum entanglement and to thereby obtain a strong Bell parameter of 3 1/5. I theoretically demonstrate various orthogonal relations between two quantum states, each of which is a state with a rotational symmetry superposition made up of n fractional orbital angular momentum states, where n ∈ N. I propose a Bell inequality experiment with two n-section spiral phase plates that have these two quantum states, whereby various angle periods with parabolic coincident fringes 2π/n and Bell’s parameter 3 1/5 in each period can be obtained.
关键词： Bell inequality,orbital angular momentum,spiral phase plates,high-dimensional entanglement,parabolic coincident fringes
更新于2025-09-09 09:28:46
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Wavefront reconstruction of vortex beams via a simplified transport of intensity equation and its symmetry based error reduction
摘要： We present an unexplored non-interferometric approach for wavefront measurement of vortex beams based on the transport of intensity equation. By exploiting the symmetries of vortexes we are able to simplify the transport of intensity equation to a reduced expression not reported before in the context of phase imaging. This reduced model can be solved to measure the phase profile of vortexes via one-dimensional operations only without the complexities pertaining the regular transport of intensity equation. We also use the axial symmetry exhibited by the intensity profile of vortexes to build a noise filtering scheme exclusive to circularly symmetric images and thus address electronic noise in digital imaging systems. We present a series of numerical experiments both to clarify how to apply our proposal step by step and to prove its overall functionality.
关键词： optics,free-space,orbital angular momentum,noisy data,axial symmetry,quantitative phase imaging,non-interferometric techniques,optical vortex
更新于2025-09-09 09:28:46
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[IEEE 2018 IEEE International Conference on Computational Electromagnetics (ICCEM) - Chengdu, China (2018.3.26-2018.3.28)] 2018 IEEE International Conference on Computational Electromagnetics (ICCEM) - Polarization-Controllable Orbital Angular Momentum Using Anisotropic Coding Metasurfaces
摘要： In the past few years, the orbital angular momentum (OAM) has aroused great interests within scientific communities, showing great potentials to enhance capacities in radio, optical and quantum coding metasurface is proposed to generate multiple polarization controllable OAM vortex beams at microwave frequencies. A phase compensation theory is put forward to determine the array pattern of the metasurface, enabling the generation of vortex beams with arbitrary polarization. The metasurface is composed of anisotropic elements, whose reflection phases can be engineered and encoded separately along different polarization directions. The simulation results demonstrate that multiple OAM vortex beams can be generated as expected, with each of them polarized in a controlled manner. The proposed avenue shows great potentials for the application of polarization division multiplexing in OAM communication systems.
关键词： polarization multiplexing,coding metasurface,Orbital angular momentum,radio frequency
更新于2025-09-09 09:28:46