The Experts below are selected from a list of 4893 Experts worldwide ranked by ideXlab platform
Xiaocong Yuan - One of the best experts on this subject based on the ideXlab platform.
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Spin-resolved near-field scanning optical microscopy for mapping of the Spin Angular Momentum distribution of focused beams
Applied Physics Letters, 2020Co-Authors: Xiaojin Yin, Peng Shi, Xiaocong YuanAbstract:We proposed and built a near-field scanning optical microscope (NSOM) to enable the characterization of the Spin Angular Momentum (SAM) distribution of electromagnetic fields with nanoscale resolution. The NSOM probe was composed of a circular nanohole formed in a thick gold film that was deposited on a tapered cone fiber. The near-field signal, when coupled through the nanohole to the fiber, was split and analyzed using a combination of a quarter-wave plate and a polarizer to extract the two circular polarization components of the signal. This allowed us to characterize the out-of-plane SAM component, which was determined using the relationship Sz ∝ IRCP − ILCP. Using the developed system, we mapped the SAM distributions of a variety of tightly focused cylindrical vector vortex beams and thus validated the system's effectiveness. The proposed Spin-resolved NSOM could be a valuable tool for studies of both near-field Spin optics and topological photonics.
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Structured Spin Angular Momentum in highly focused cylindrical vector vortex beams for optical manipulation.
Optics express, 2018Co-Authors: Peng Shi, Xiaocong YuanAbstract:We investigate the Spin properties of a family of cylindrical vector vortex beams under a focusing condition. The Spin-orbit interaction is demonstrated by comparing the energy flow and Spin flow density of the focused field to those of the incident field. This Spin-orbit interaction is analyzed to construct the desired distribution of Spin Angular Momentum for optical manipulation. The structured Spin Angular Momentum of the focused field can transfer to the optical torque for the non-magnetic absorptive particle. The influences of polarization topological charge, vortex topological charge and wavelength on optical torque in the hot-spot of focused field are summarized for three typical particles. Such results may be exploited in practical optical manipulation, particularly for optically induced rotations.
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transfer of pure on axis Spin Angular Momentum to the absorptive particle using self imaged bottle beam optical tweezers system
Optics Express, 2004Co-Authors: Balpreet Singh Ahluwalia, Xiaocong YuanAbstract:Optical tweezers system has aggrandized the understanding of the light-matter interaction and is used frequently to transfer Angular Momentum of light to microscopic particles. Here we demonstrate experimentally, for the first time to our knowledge the use of self-imaged bottle beam in an optical tweezers system and we report the mechanical transfer of ‘pure’ on-axis Spin Angular Momentum to an absorptive particle. The self-imaged bottle beam has embedded optical bottles or null intensity points where the absorptive particles are trapped and the transfer of Spin Angular Momentum is accomplished without the default transfer of orbital Angular Momentum of a singular beam, which are used conventionally to trap absorptive particles.
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Transfer of ‘pure’ on-axis Spin Angular Momentum to the absorptive particle using self-imaged bottle beam optical tweezers system
Optics express, 2004Co-Authors: Balpreet Singh Ahluwalia, Xiaocong Yuan, S. H. TaoAbstract:Optical tweezers system has aggrandized the understanding of the light-matter interaction and is used frequently to transfer Angular Momentum of light to microscopic particles. Here we demonstrate experimentally, for the first time to our knowledge the use of self-imaged bottle beam in an optical tweezers system and we report the mechanical transfer of 'pure' on-axis Spin Angular Momentum to an absorptive particle. The self-imaged bottle beam has embedded optical bottles or null intensity points where the absorptive particles are trapped and the transfer of Spin Angular Momentum is accomplished without the default transfer of orbital Angular Momentum of a singular beam, which are used conventionally to trap absorptive particles.
László B Szabados - One of the best experts on this subject based on the ideXlab platform.
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On certain quasi-local Spin-Angular Momentum expressions for large spheres near the null infinity
Classical and Quantum Gravity, 2001Co-Authors: László B SzabadosAbstract:The recently suggested quasi-local Spin-Angular Momentum expressions, based on the Bramson superpotential and on the holomorphic or anti-holomorphic Spinor fields, are calculated for large spheres near the future null infinity of asymptotically flat Einstein–Maxwell spacetimes. It is shown that although the expression based on the anti-holomorphic Spinors is finite and unambiguously defined only in the centre-of-mass frame (i.e. it diverges in general), the corresponding Pauli–Lubanski Spin is always finite, free of gauge ambiguities and is built only from the gravitational data. Thus it defines a gravitational Spin expression at the future null infinity. The construction based on the holomorphic Spinors diverges in the presence of outgoing gravitational radiation. For stationary spacetimes both constructions reduce to the 'standard' expression.
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On certain quasi-local Spin-Angular Momentum expressions for small spheres
Classical and Quantum Gravity, 1999Co-Authors: László B SzabadosAbstract:The Ludvigsen-Vickers and two recently suggested quasi-local Spin-Angular Momentum expressions, based on holomorphic and anti-holomorphic Spinor fields, are calculated for small spheres of radius r about a point o. It is shown that, apart from the sign in the case of anti-holomorphic Spinors in non-vacuum, the leading terms of all these expressions coincide. In non-vacuum spacetimes this common leading term is of order r4, and it is the product of the contraction of the energy-Momentum tensor and an average of the approximate boost-rotation Killing vector that vanishes at o and of the 3-volume of the ball of radius r. In vacuum spacetimes the leading term is of order r6, and the factor of proportionality is the contraction of the Bel-Robinson tensor and another average of the same approximate boost-rotation Killing vector.
Yiping Cui - One of the best experts on this subject based on the ideXlab platform.
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Conservation of the Spin Angular Momentum in second-harmonic generation with elliptically polarized vortex beams
Applied Physics Letters, 2019Co-Authors: Liu Tianyu, Guanghao Rui, Yiping CuiAbstract:Spin-to-orbital Angular Momentum conversion and orbital Angular Momentum conservation in the harmonic generation process have been extensively investigated. However, very few studies have focused on the Spin Angular Momentum (SAM) conservation in the nonlinear optical process. Herein, we investigate the SAM characteristics of the second-harmonic waves with weakly focused elliptically polarized vortex beams (EPVBs). It is shown that the chirality of the second-harmonic wave is always opposite to that of the fundamental wave. Moreover, the absolute value of SAM satisfies the conservation law in the second-harmonic process generated by weakly focused EPVBs. The results are in good agreement with the experimental observations.Spin-to-orbital Angular Momentum conversion and orbital Angular Momentum conservation in the harmonic generation process have been extensively investigated. However, very few studies have focused on the Spin Angular Momentum (SAM) conservation in the nonlinear optical process. Herein, we investigate the SAM characteristics of the second-harmonic waves with weakly focused elliptically polarized vortex beams (EPVBs). It is shown that the chirality of the second-harmonic wave is always opposite to that of the fundamental wave. Moreover, the absolute value of SAM satisfies the conservation law in the second-harmonic process generated by weakly focused EPVBs. The results are in good agreement with the experimental observations.
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Varying polarization and Spin Angular Momentum flux of radially polarized beams by anisotropic Kerr media.
Optics letters, 2016Co-Authors: Bo Wen, Guanghao Rui, Yuxiong Xue, Qiwen Zhan, Yiping CuiAbstract:Light fields with structured polarization distribution interacting with structured media will result in many novel optical effects in both the linear and nonlinear regimes. In this work, we report a theoretical investigation of both vectorial self-diffraction behaviors and polarization evolution characteristics of a radially polarized beam induced by anisotropic Kerr nonlinearity. By taking the polarization–orientation dependence of the third-order refractive nonlinearity, we study the far-field vectorial self-diffraction patterns of the radially polarized beam using the vectorial Rayleigh–Sommerfeld formulas. Numerical results reveal that the self-diffraction patterns with a four-fold rotational symmetry exhibit hybrid states of polarization. Moreover, the interaction of radially polarized beams with the anisotropic nonlinear Kerr media leads to the redistribution of the Spin Angular Momentum (SAM) flux in the far-field plane. The presented work opens up new avenues for varying polarization and SAM through anisotropic optical nonlinearity.
Misha Ivanov - One of the best experts on this subject based on the ideXlab platform.
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Spin conservation in high order harmonic generation using bicircular fields
Physical Review A, 2014Co-Authors: Emilio Pisanty, Suren Sukiasyan, Misha IvanovAbstract:We present an alternative theoretical model for a recent experiment [A.Fleischer et al., Nature Photon. 8, 543 (2014)] which used bichromatic, counter-rotating high intensity laser pulses to probe the conservation of Spin Angular Momentum in high harmonic generation. We separate elliptical polarizations into independent circular fields with definite Angular Momentum, instead of using the expectation value of Spin for each photon in the conservation equation, and we find good agreement with the experimental results. In our description the generation of each individual harmonic conserves Spin Angular Momentum, in contrast to the model proposed by Fleischer et al. Our model also correctly describes analogous processes in standard perturbative optics.
Yanfeng Zhang - One of the best experts on this subject based on the ideXlab platform.
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Spin-orbit interaction of light induced by transverse Spin Angular Momentum engineering
Nature communications, 2018Co-Authors: Zengkai Shao, Jiangbo Zhu, Yujie Chen, Yanfeng ZhangAbstract:The investigations on optical Angular momenta and their interactions have broadened our knowledge of light’s behavior at sub-wavelength scales. Recent studies further unveil the extraordinary characteristics of transverse Spin Angular Momentum in confined light fields and orbital Angular Momentum in optical vortices. Here we demonstrate a direct interaction between these two intrinsic quantities of light. By engineering the transverse Spin in the evanescent wave of a whispering-gallery-mode-based optical vortex emitter, a Spin-orbit interaction is observed in generated vortex beams. Inversely, this unconventional Spin-orbit interplay further gives rise to an enhanced Spin-direction locking effect in which waveguide modes are unidirectionally excited, with the directionality jointly controlled by the Spin and orbital Angular momenta states of light. The identification of this previously unknown pathway between the polarization and spatial degrees of freedom of light enriches the Spin-orbit interaction phenomena, and can enable various functionalities in applications such as communications and quantum information processing.
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Spin orbit interaction of light induced by transverse Spin Angular Momentum engineering
arXiv: Optics, 2017Co-Authors: Zengkai Shao, Jiangbo Zhu, Yujie Chen, Yanfeng ZhangAbstract:We report the first demonstration of a direct interaction between the extraordinary transverse Spin Angular Momentum in evanescent waves and the intrinsic orbital Angular Momentum in optical vortex beams. By tapping the evanescent wave of whispering gallery modes in a micro-ring-based optical vortex emitter and engineering the transverse Spin state carried therein, a transverse-Spin-to-orbital conversion of Angular Momentum is predicted in the emitted vortex beams. Numerical and experimental investigations are presented for the proof-of-principle demonstration of this unconventional interplay between the Spin and orbital Angular momenta, which could provide new possibilities and restrictions on the optical Angular Momentum manipulation techniques on the sub-wavelength scale. This phenomenon further gives rise to an enhanced Spin-direction coupling effect in which waveguide or surface modes are unidirectional excited by incident optical vortex, with the directionality jointly controlled by Spin-orbit states. Our results enrich the Spin-orbit interaction phenomena by identifying a previously unknown pathway between the polarization and spatial degrees of freedom of light, and can enable a variety of functionalities employing Spin and orbital Angular momenta of light in applications such as communications and quantum information processing.
