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Berkhout GC Lavery MP Courtial J Beijersbergen MW Padgett MJ 《Physical review letters》2010,105(15):153601
We present a method to efficiently sort orbital angular momentum (OAM) states of light using two static optical elements. The optical elements perform a Cartesian to log-polar coordinate transformation, converting the helically phased light beam corresponding to OAM states into a beam with a transverse phase gradient. A subsequent lens then focuses each input OAM state to a different lateral position. We demonstrate the concept experimentally by using two spatial light modulators to create the desired optical elements, applying it to the separation of eleven OAM states. 相似文献
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Jian Wang 《中国科学:物理学 力学 天文学(英文版)》2019,(3)
Angular momentum, a fundamental physical quantity, can be divided into spin angular momentum(SAM) and orbital angular momentum(OAM) in electromagnetic waves. Helically-phased or twisted light beams carrying OAM that exploit the spatial structure physical dimension of electromagnetic waves have benefited wide applications ranging from optical manipulation to quantum information processing. Using the two distinct properties of OAM, i.e., inherent orthogonality and unbounded states in principle, one can develop OAM modulation and OAM multiplexing techniques for twisted optical communications. OAM multiplexing is an alternative space-division multiplexing approach employing an orthogonal mode basis related to the spatial phase structure. In this paper, we review the recent progress in twisted optical communications using OAM in free space and fiber. The basic concept of momentum, angular momentum, SAM, OAM and OAM-carrying twisted optical communications,key techniques and devices of OAM generation/(de)multiplexing/detection, high-capacity spectrally-efficient free-space OAM links, fiber-based OAM links, and OAM processing functions are presented. Ultra-high spectral efficiency and petabit-scale freespace data links are achieved benefiting from OAM multiplexing. The key techniques and challenges of twisted optical communications are also discussed. Twisted optical communications using OAM are compatible with other existing physical dimensions such as frequency/wavelength, amplitude, phase, polarization and time, opening a possible way to facilitate continuous increase of the aggregate transmission capacity and spectral efficiency through N-dimensional multiplexing. 相似文献
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光子轨道角动量量子态具有高维和光学涡旋特性, 在经典和量子领域展示出了巨大的应用潜力, 目前对其的研究已成为物理学的一个热点. 本实验研究了利用Sagnac干涉仪干涉的方法将具有不同轨道角动量的光束无破坏地分离到不同的路径, 即实现光子轨道角动量分束器. 实验中利用此分束器验证了对几种不同轨道角动量态(包含叠加态)的分离, 得到了与理论预期相符的实验结果. 这种对轨道角动量态的区分的方法相比已有的其他区分方法具有较好的稳定性, 而且可用于区分叠加态, 也可以达到单光子水平, 最重要的是实现了不同的轨道角动量本征态无破坏的与路径比特耦合. 这种新方法对高密度通信、量子纠缠、量子保密通信、量子计算与量子信息等方面有着重要的意义. 相似文献
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《中国光学快报(英文版)》2019,(10)
Inspired by recent rapid deep learning development, we present a convolutional-neural-network(CNN)-based algorithm to predict orbital angular momentum(OAM) mode purity in optical fibers using far-field patterns.It is found that this image-processing-based technique has an excellent ability in predicting the OAM mode purity, potentially eliminating the need of using bulk optic devices to project light into different polarization states in traditional methods. The excellent performance of our algorithm can be characterized by a prediction accuracy of 99.8% and correlation coefficient of 0.99994. Furthermore, the robustness of this technique against different sizes of testing sets and different phases between different fiber modes is also verified. Hence, such a technique has a great potential in simplifying the measuring process of OAM purity. 相似文献
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Generation of a large orbital angular momentum beam via an optical fiber winding around a curved path and its application
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《中国物理 B》2021,30(10):104208-104208
Many papers have been published on the study of orbital angular momentum(OAM) of the laser modes based on the Laguerre–Gaussian(LG) beam and helical phase plate or rotating cylindrical lens, and the principal ray of the LG beam remains straight line. These ways are difficult to get a large OAM modes. In this paper, we propose a novel method to prepare a large OAM modes when the light propagates through a optical fiber winding around a curved path, and establish a theoretical framework based on the principal ray path changing. Firstly, we investigate three kinds of winding structure.Secondly, based on the analytical solutions and numerical calculations, we can find that the spiral body can achieve a large OAM temporal pulse. At the same time, based on the zero OAM diffraction diagram, we can obtain an improvement of resolving power beyond Rayleigh's criterion. Finally, applying a large OAM diffraction pattern to realize 12-bitencodes,we can obtain a high-security optical information transfer system. 相似文献
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涡旋光束是一种携带有轨道角动量的光束,在光学扳手、光通信、旋转探测等领域具有重要的应用价值.由于轨道角动量态是涡旋光束的特征值,因此如何探测光束的轨道角动量态分布至关重要.国内外学者已经提出了多种探测涡旋光束的技术,如干涉法、衍射光栅法、多普勒分析法、超材料表面法等.这些技术中,衍射光栅测量法较为简单易行,应用较广.本综述主要介绍了几种当前利用衍射光栅测量涡旋光束轨道角动量态的主流方法,同时也介绍了如何利用衍射光栅来测量光束的轨道角动量谱. 相似文献
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Y Yan Y Yue H Huang JY Yang MR Chitgarha N Ahmed M Tur SJ Dolinar AE Willner 《Optics letters》2012,37(17):3645-3647
We propose an approach to efficiently generate and multiplex optical orbital angular momentum (OAM) modes in a fiber with a ring refractive index profile by using multiple coherent inputs from a Gaussian mode. By controlling the phase relationship of the multiple inputs, one can selectively generate OAM modes of different states l. By controlling both the amplitude and phase of the multiple inputs, multiple OAM modes can be generated simultaneously without additional loss coming from multiplexing. We show, by simulation, the generation of OAM modes (OAM state |l|<3) with mode purity greater than 99%. The power loss of generating and multiplexing seven modes is about 35%. A transmitter for an OAM-based mode-division multiplexing system is proposed based on the discrete Fourier transform between the data carried by the multiple inputs and the data carried by the OAM modes. The experimental implementation of the proposed approach could be achieved by integrating ring fiber, multicore fiber, and photonic integrated circuit technology. 相似文献
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《中国光学快报(英文版)》2021,(6)
Based on nonlinear wave mixing, we experimentally propose a scheme for directly generating optical orbital angular momentum(OAM) by a spirally structured fundamental wave interacting with a nonlinear medium, in which the nonlinear susceptibilities are homogenous. In the experiment, the second-harmonic generation of a fundamental wave carrying positive(negative) integers and fractional OAM states was investigated. This study presents a convenient approach for dynamic control of OAM of vortex beams, which may feature their applications in optical manipulation and optical communication. 相似文献
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传统的沿z轴光纤传输光线的轨道角动量(orbital angular momentum,OAM)光束的制备方法共同之处都是从内部结构着想,光束的主光线基本上不变,只是波面在变.但要获得携带高mh的光有一定的难度.针对上述问题,本文建立以波面不变,光束主光线变化为基础的理论框架,利用微分几何理论验证不沿z轴圆柱型光纤螺线圈传输的光线可以携带高mh OAM的理论设想.研究发现:利用流动坐标(α,β,γ)计算光线在绕圆柱体的光纤中传输时光纤截面的衍射分布图呈现涡旋特征,有高阶OAM模式.当θ=θ0时,圆柱形轨道光纤过渡到直线轨道光纤.计算光线沿直线传输时光纤截面的衍射分布图是Airy斑,即圆孔衍射斑,无高阶OAM模式. 相似文献
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Christian Cuadrado-Laborde Pablo A. Costanzo-Caso Enrique E. Sicre 《Optics Communications》2006,266(1):32-38
Based on the space-time duality and the temporal imaging theory, an optical implementation of the Radon-Wigner transform in the time domain is proposed for analyzing the propagation of ultrashort light pulses in guided dispersive media. As an application of this approach, we discuss the temporal selfimaging or Talbot effect originated by a periodic pulse train. The frequency chirp of the pulses is also considered in order to evaluate its effect on both the integer and the fractional selfimages. 相似文献
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We have developed a novel source for the generation of powerful phase-coherent light pulses. Our setup uses an acousto-optic modulator (AOM) inside an external high-finesse resonator. By applying a short rf pulse to the AOM, we dump the cavity and extract a large part of the stored and enhanced power within a short optical pulse and with a controllable optical phase. In preliminary experiments we reached 100 W of peak power in a 15-ns optical pulse. The mutual phase coherence of successive light pulses is demonstrated with a molecular iodine interferometer experiment in a cell. 相似文献
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An experimental system consisting of a Dove prism embedded Mach-Zehnder (M-Z) interferometer and two gratings was built to sort and detect orbital angular momentum (OAM) states of light beams. The helical beams with different OAM states were generated by propagating the fundamental-mode Gaussian beam through a spatial light modulator. The Dove prism embedded M-Z interferometer was used to sort helical beams with odd or even OAM number and two binary amplitude gratings were used to measure the OAM states. Sorting of coaxially-superposed coherent and incoherent helical beams with odd and even OAM states was realized in the experiment. 相似文献
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Wenzhuo Tang 《Physics letters. A》2010,374(21):2183-2187
Slow light of four different pulses are demonstrated and analyzed in cesium vapor based on electromagnetically induced transparency. Each pulse, generated with an identical temporal width, experiences very different slow light effects due to its temporal and spectral distributions simultaneously. Aiming at the applications such as timing, instead of communication, we obtained two optimized ones among the four different shaped pulses. Firstly, the single-exponential pulse is more appropriate to maximize the time delay than other three pulses; secondly, the cosine pulse shows advantage to minimize the distortion (broadening) of the slowed pulse. Finally, using optical filter model, we present a convenient simulation method in theory; moreover, the theoretical results show excellent agreement with experiments. 相似文献
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Staudt MU Afzelius M de Riedmatten H Hastings-Simon SR Simon C Ricken R Suche H Sohler W Gisin N 《Physical review letters》2007,99(17):173602
High-visibility interference of photon echoes generated in spatially separated solid-state atomic ensembles is demonstrated. The solid-state ensembles were LiNbO(3) waveguides doped with erbium ions absorbing at 1.53 microm. Bright coherent states of light in several temporal modes (up to 3) are stored and retrieved from the optical memories using two-pulse photon echoes. The stored and retrieved optical pulses, when combined at a beam splitter, show almost perfect interference, which demonstrates both phase preserving storage and indistinguishability of photon echoes from separate optical memories. By measuring interference fringes for different storage times, we also show explicitly that the visibility is not limited by atomic decoherence. These results are relevant for novel quantum-repeater architectures with photon-echo based multimode quantum memories. 相似文献
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We use a unique multifocal multiphoton microscope to directly characterize the pulse in the focal plane of a high-NA objective using second-harmonic generation frequency-resolved optical gating (FROG). Because of the nature of the optical setup, femtosecond laser pulses of orthogonal polarization states are generated in the focal plane, each acquiring a different spectral dispersion. By applying an additional constraint on the phase extraction algorithm, we simultaneously extract both the gate and probe pulses from a single spectrogram with a FROG error of 0.016. 相似文献