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Recognizing the orbital angular momentum(OAM)of vortex beams from speckle patterns

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Science China(Physics,Mechanics & Astronomy) 2022年第4期65卷 55-61页

作者： Zhiyuan Wang Xuetian Lai Huiling Huang Xiaoyan Wang Haoran Li Ziyang Chen Jun Han Jixiong Pu Fujian Key Laboratory of Light Propagation and Transformation College of Information Science and EngineeringHuaqiao UniversityXiamen 361021China Quanzhou Institute of Equipment Manufacturing Fujian Institute of Research on the Structure of MatterChinese Academy of SciencesQuanzhou 362000China

The orbital angular momentum(OAM)of vortex beams offers a new degree for information encoding,which has been applied to optical *** measurement is essential for these applications,and has been realized in free space by several ***,these methods are inapplicable to estimate the OAM of vortex beams directly from the speckle patterns in the exit end of a multimode fiber(MMF).To tackle this issue,we design a convolutional neural network(CNN)to realize 100%accuracy recognition of two orthogonally polarized OAM modes from speckle ***,we demonstrate that even when the speckle patterns are cropped to only 1/64 of the original patterns,the recognition accuracy of the designed neural network is still higher than 98%.We also study the recognition accuracy of cropped speckles in different areas of speckle patterns to verify the feasibility of OAM recognition after *** results demonstrate that recognizing the OAMs of two orthogonally polarized vortex beams from only a portion of speckle patterns in the exit end of an MMF is feasible,offering the potential to construct a 1×N data transmission scheme.

关键词： optical angular momentum speckle pattern orthogonal polarization fiber optical communication deep learning

The Wigner distribution functions of coherent and partially coherent Bessel-Gaussian beams

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Chinese Physics B 2012年第3期21卷 208-211页

作者：朱开成李绍新唐英余燕唐慧琴 School of Physical Science and Technology Central South University Physical Staff Room Guangdong Medical College

Based on the integral representation of the Bessel functions and the generating function of the Tricomi function, an analytical expression of the Wigner distribution function （WDF） for a coherent or partially coherent Bessel Gaussian beam is presented. The reduced two-dimensional WDFs are also demonstrated graphically, which reveals the dependence of the reduced WDFs on the beam parameters.

关键词： partially coherent Bessel-Gaussian beam Wigner function optical angular momentum

Quantization of electromagnetic modes and angular momentum on plasmonic nanowires

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Chinese Physics B 2020年第8期29卷 428-436页

作者：朱国栋郭杨喆董斌方蔚瑞 Key Laboratory of Materials Modification by Laser Electronand Ion Beams(Ministry of Education)School of PhysicsDalian University of TechnologyDalian 116024China Key Laboratory of New Energy and Rare Earth Resource Utilization of State Ethnic Affairs Commission Key Laboratory of Photosensitive Materials&Devices of Liaoning ProvinceSchool of Physics and Materials EngineeringDalian Nationalities UniversityDalian 116600China

Quantum theory of surface plasmons is very important for studying the interactions between light and different metal nanostructures in *** this work,using the canonical quantization method,the SPPs on nanowires and their orbital and spin angular momentums are *** results show that the SPPs on nanowire carry both orbital and spin momentums during ***,the result is applied to the plasmonic nanowire waveguide to show the agreement of the *** study is helpful for the nano wire based plasmonic interactions and the quantum information based optical circuit in the future.

关键词： surface plasmons surface waves optical angular momentum

Generation of all-fiber femtosecond vortex laser based on NPR mode-locking and mechanical LPG

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Chinese Optics Letters 2018年第11期16卷 5-8页

作者：张志明魏薇唐莉勤杨洁郭杰伟丁镭李乙钢 school of physics nankai universityTianjin 300071 China

An all-fiber femtosecond vortex laser based on common fiber components is constructed. It can produce femtosecond orbital angular momentum modes whose time pulse width is 398 fs. The topological charge of output orbital angular momentum （OAM） modes from this laser can be adjusted among 0, ＋1, and -1 easily while it is also easy to convert between continuous OAM modes and pulse OAM modes.

关键词： Femtosecond lasers Laser modes Long period gratings Mode locking optical angular momentum

Experimental determination of the azimuthal and radial mode orders of a partially coherent LGpl beam(Invited Paper)

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Chinese Optics Letters 2017年第3期15卷 2-6页

作者：刘显龙吴腾飞刘琳赵承良蔡阳健 College of Physics Optoelectronics and Energy & Collaborative Innovation Center of Suzhou Nano Science and Technology Soochow University Suzhou 215006 China Key Lab of Advanced optical Manufacturing Technologies of Jiangsu Province and Key Lab of Modern optical Technologies of Education Ministry of China Soochow University Suzhou 215006 China

It is known that one can determine the mode orders （i.e., the azimuthal order and radial order） of a partially coherent LGpl beam （i.e., a partially coherent vortex beam） based on the measurement of the cross-correlation function （CCF） and the double correlation function （DCF） together. The technique for measuring the CCF is known. In this Letter, we propose a method for measuring the DCF. Based on the proposed method, the deter- mination of the mode orders of a partially coherent LGpll beam is demonstrated experimentally.

关键词： Cylindrical lenses optical angular momentum Phase plates Spatial light modulators Spiral phase Vortex beams

Gravitational field around black hole induces photonic spin-orbit interaction that twists light

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Frontiers of physics 2017年第5期12卷 87-90页

作者： Deng Pan Hong-Xing Xu School of Physics and Technology Wuhan University Wuhan 430072 China

The spin-orbit interaction （SOI） of light has been intensively studied in nanophotonics because it enables sensitive control of photons＇ spin degree of freedom and thereby the trajectories of the photons, which is useful for applications such as signal encoding and routing. A recent study [Phys. Rev. Lett. 117, 166803 （2016）] showed that the SOI of photons manifests in the presence of a gradient in the permittivity of the medium through which the photons propagate; this enhances the scattering of circularly polarized light and results in the photons propagating along twisted trajectories. Here we theoretically predict that, because of the equivalence between an inhomogeneous dielectric medium and a gravitational field demonstrated in transformation optics, a significant SOI is induced onto circularly polarized light passing by the gravitational lens of a black hole. This leads to： i） the photons to propagate along chiral trajectories if the size of the black hole is smaller than the wavelength of the incident photons; ii） the resulting image of the gravitational lens to manifest an azimuthal rotation because of these chiral trajectories. The findings open for a way to probe for and discover subwavelength-size black holes using circularly polarized light.

关键词： spin-orbit interation black hole gravitational lens optical angular momentum