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Journal articles on the topic 'Vortex .OAM'

Author: Grafiati
Published: 4 June 2021
Last updated: 1 February 2022

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1

Zhang, Zhifeng, Xingdu Qiao, Bikashkali Midya, Kevin Liu, Jingbo Sun, Tianwei Wu, Wenjing Liu, et al. "Tunable topological charge vortex microlaser." Science 368, no. 6492 (May 14, 2020): 760–63. http://dx.doi.org/10.1126/science.aba8996.

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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.
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2

Na Liu, Laura. "Plasmonic vortex cavities multiply OAM." Science 373, no. 6556 (August 12, 2021): 754.19–756. http://dx.doi.org/10.1126/science.373.6556.754-s.

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3

Volyar, A. V., M. V. Bretsko, Ya E. Akimova, Yu A. Egorov, and V. V. Milyukov. "Sectorial perturbation of vortex beams: Shannon entropy, orbital angular momentum and topological charge." Computer Optics 43, no. 5 (October 2019): 723–34. http://dx.doi.org/10.18287/2412-6179-2019-43-5-723-734.

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Transformations of the vortex beams structure subjected to sectorial perturbation were theoretically and experimentally studied. The analysis was based on computing (measuring) the vortex spectrum that enables us to find the orbital angular momentum (OAM) and Shannon entropy (informational entropy). We have revealed that, in the general case, the number of vortices caused by an external perturbation is not related to the topological charge. For arbitrary perturbation, the topological charge remains equal to the initial topological charge of the unperturbed vortex beam. Growth of the vortex number induced by perturbations is associated with the optical uncertainty principle between the sectorial angle and the OAM. The computer simulation has shown that OAM does not depend on the number of vortices induced by perturbations. Moreover, two maxima are formed both in the positive and negative regions of the vortex spectrum. As a result, the OAM does not practically change in a wide range of perturbation angles from 0 to 90 °. However, at large perturbation angles, when the energy is almost equally redistributed between the vortex modes with opposite signs of the topological charge, the OAM rapidly decreases. At the same time, the Shannon entropy monotonically increases with growing perturbation angle. This is due to the fact that the entropy depends only on the number of vortex states caused by external perturbations.
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4

Wang, Xingyuan, Xiaoyong Hu, and Tianrui Zhai. "Vortex Laser Based on a Plasmonic Ring Cavity." Crystals 11, no. 8 (July 31, 2021): 901. http://dx.doi.org/10.3390/cryst11080901.

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The orbital angular momentum (OAM) of the structure light is viewed as a candidate for enhancing the capacity of information processing. Microring has advantages in realizing the compact lasers required for on-chip applications. However, as the clockwise and counterclockwise whispering gallery modes (WGM) appear simultaneously, the emitted light from the normal microring does not possess net OAM. Here, we propose an OAM laser based on the standing-wave WGMs containing clockwise and counterclockwise WGM components. Due to the inhomogeneous intensity distribution of the standing-wave WGM, the single-mode lasing for the OAM light can be realized. Besides, the OAM of the emitted light can be designed on demand. The principle and properties of the proposed laser are demonstrated by numerical simulations. This work paves the way for exploring a single-mode OAM laser based on the plasmonic standing-wave WGMs at the microscale, which can be served as a basic building block for on-chip optical devices.
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5

MEHMOOD, M. Q., CHENG-WEI QIU, AARON DANNER, and JINGHUA TENG. "GENERATION OF OPTICAL VORTEX BEAMS BY COMPACT STRUCTURES." Journal of Molecular and Engineering Materials 02, no. 02 (June 2014): 1440013. http://dx.doi.org/10.1142/s2251237314400139.

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Orbital angular momentum (OAM) has been an enthralling topic of research from fundamental physics to technological applications since its discovery in 1992. Many techniques have been developed to generate OAM such as using spiral phase plates (SPPs), computer-generated holograms (CGH) and cylindrical mode converters, etc. However, these methods are based on bulky optics that cause a major hindrance for their exploitation in the emerging area of micron-nanophotonics. Recently, generation of such helical beams by micron-sized structures has gained momentous interest to make their appliance possible at small scale. This paper recapitulates these endeavors of minuscule optical vortex generation. Five different types of compact optical vortex generators, i.e., downscaling of conventional OAM generators, plasmonic vortex lens (PVLs), metasurfaces, integrated OAM emitters and subwavelength apertures are brought under discussion.
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6

Bu, Xiangxi, Zhuo Zhang, Xingdong Liang, Longyong Chen, Haibo Tang, Zheng Zeng, and Jie Wang. "A Novel Scheme for MIMO-SAR Systems Using Rotational Orbital Angular Momentum." Sensors 18, no. 10 (October 18, 2018): 3511. http://dx.doi.org/10.3390/s18103511.

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The vortex electromagnetic (EM) wave with orbital angular momentum (OAM) brings a new degree of freedom for synthetic aperture radar (SAR) imaging, although to date, its application to multi-input multi-output (MIMO) SAR has not yet been widely reported. In this paper, an orbital angular momentum (OAM)-based MIMO-SAR system is proposed. The rotational Doppler Effect (RDE) of vortex EM waves offers a novel scheme for an OAM-based MIMO-SAR system. By transmitting the rotational vortex EM waves, echoes of different OAM modes can be discriminated by a bandpass filter in the range-Doppler domain. The performance of the proposed scheme is independent of the time-variant channel responses, and the wider beam width of the vortex EM waves delivers, for the same antenna aperture size, better performance in terms of swath width and azimuth resolution, in contrast to the plane EM waves. Moreover, the spatial diversity of vortex EM waves shows great potential to enhance the MIMO-SAR system applications, which involve high-resolution wide-swath remote sensing, 3-D imaging, and radar-communication integration. The proposed scheme is verified by proof-of-concept experiments. This work presents a new application of vortex EM waves, which facilitates the development of new-generation and forthcoming SAR systems.
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7

Borda-Hernández, José A., Claudia M. Serpa-Imbett, and Hugo E. Hernandez Figueroa. "Vortex Polymer Optical Fiber with 64 Stable OAM States." Polymers 12, no. 12 (November 24, 2020): 2776. http://dx.doi.org/10.3390/polym12122776.

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This research introduces a numerical design of an air-core vortex polymer optical fiber in cyclic transparent optical polymer (CYTOP) that propagates 32 orbital angular momentum (OAM) modes, i.e., it may support up to 64 stable OAM-states considering left- and right-handed circular polarizations. This fiber seeks to be an alternative to increase the capacity of short-range optical communication systems multiplexed by modes, in agreement with the high demand of low-cost, insensitive-to-bending and easy-to-handle fibers similar to others optical fibers fabricated in polymers. This novel fiber possesses unique characteristics: a diameter of 50 µm that would allow a high mechanical compatibility with commercially available polymer optical fibers, a difference of effective index between neighbor OAM modes of around 10−4 over a bandwidth from 1 to 1.6 µm, propagation losses of approximately 15 × 10−3 dB/m for all OAM modes, and a very low dispersion for OAM higher order modes (±l = 16) of up to +2.5 ps/km-nm compared with OAM lower order modes at a telecom wavelength of 1.3 µm, in which the CYTOP exhibits a minimal attenuation. The spectra of mutual coupling coefficients between modes are computed considering small bends of up to 3 cm of radius and slight ellipticity in the ring of up to 5%. Results show lower-charge weights for higher order OAM modes.
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8

Yang, Jingxuan, Hu Zhang, Xiaoguang Zhang, Hui Li, and Lixia Xi. "Transmission Characteristics of Adaptive Compensation for Joint Atmospheric Turbulence Effects on the OAM-Based Wireless Communication System." Applied Sciences 9, no. 5 (March 3, 2019): 901. http://dx.doi.org/10.3390/app9050901.

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Atmospheric turbulence has an impact on the transmission of electromagnetic vortex waves with an orbital angular momentum (OAM) mode. In this paper, based on the joint atmospheric turbulence model, we examine the influence of atmospheric turbulence on the transmission of electromagnetic vortex waves. First, a mathematical model is established to formulate the transmission characteristics of electromagnetic vortex waves under joint atmospheric turbulence. Subsequently, in order to mitigate the influence of the atmospheric turbulence on the electromagnetic vortex waves, an adaptive compensation on phase is proposed. Finally, we analyzed the transmission performance of an OAM-mode multiplexing system using an adaptive compensation method through the wireless communication channel. By means of numerical simulation, the effect of atmospheric turbulence on the transmission characteristics and mode crosstalk of OAM is analyzed. The simulation results show that electromagnetic vortex waves could perform well on the wireless communication system with a low mode crosstalk, which provides the theoretical support to optimizing the mode division multiplexing technology in a free space communication system.
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9

Fu, Dongzhi, Hailong Zhou, Kaiwei Wang, Pei Zhang, Jianji Dong, Hong Gao, and Fuli Li. "Detecting the topological charge of a vortex beam by an arc slit diffraction." International Journal of Modern Physics B 31, no. 23 (September 14, 2017): 1750172. http://dx.doi.org/10.1142/s0217979217501727.

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The simple and efficient measurement of the light orbital angular momentum (OAM) is essential to both the classical and quantum applications with vortex beams. Here, we study the diffraction pattern in the far field when a vortex beam passes through an arc slit and demonstrate experimentally that a light spot of the diffraction pattern has a displacement which is linear to the topological charge (TC) of the incident vortex beam. Based on this property, this method is capable of measuring both modulus and sign of TC of the vortex beam. Furthermore, this scheme allows identifying multiple OAM states simultaneously.
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10

Arikawa, T., T. Hiraoka, S. Morimoto, F. Blanchard, S. Tani, T. Tanaka, K. Sakai, H. Kitajima, K. Sasaki, and K. Tanaka. "Transfer of orbital angular momentum of light to plasmonic excitations in metamaterials." Science Advances 6, no. 24 (June 2020): eaay1977. http://dx.doi.org/10.1126/sciadv.aay1977.

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The emergence of the vortex beam with orbital angular momentum (OAM) has provided intriguing possibilities to induce optical transitions beyond the framework of the electric dipole interaction. The uniqueness stems from the OAM transfer from light to material, as demonstrated in electronic transitions in atomic systems. In this study, we report on the OAM transfer to electrons in solid-state systems, which has been elusive to date. Using metamaterials (periodically textured metallic disks), we show that multipolar modes of the surface electromagnetic excitations (so-called spoof localized surface plasmons) are selectively induced by the terahertz vortex beam. Our results reveal selection rules governed by the conservation of the total angular momentum, which is confirmed by numerical simulations. The efficient transfer of light’s OAM to elementary excitations in solid-state systems at room temperature opens up new possibilities of OAM manipulation.
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11

Zhu, Liuhao, Miaomiao Tang, Hehe Li, Yuping Tai, and Xinzhong Li. "Optical vortex lattice: an exploitation of orbital angular momentum." Nanophotonics 10, no. 9 (June 9, 2021): 2487–96. http://dx.doi.org/10.1515/nanoph-2021-0139.

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Abstract Generally, an optical vortex lattice (OVL) is generated via the superposition of two specific vortex beams. Thus far, OVL has been successfully employed to trap atoms via the dark cores. The topological charge (TC) on each optical vortex (OV) in the lattice is only ±1. Consequently, the orbital angular momentum (OAM) on the lattice is ignored. To expand the potential applications, it is necessary to rediscover and exploit OAM. Here we propose a novel high-order OVL (HO-OVL) that combines the phase multiplication and the arbitrary mode-controllable techniques. TC on each OV in the lattice is up to 51, which generates sufficient OAM to manipulate microparticles. Thereafter, the entire lattice can be modulated to desirable arbitrary modes. Finally, yeast cells are trapped and rotated by the proposed HO-OVL. To the best of our knowledge, this is the first realization of the complex motion of microparticles via OVL. Thus, this work successfully exploits OAM on OVL, thereby revealing potential applications in particle manipulation and optical tweezers.
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12

Feng, Qiang, Yifeng Lin, Yushan Zheng, and Long Li. "Vortex Beam Optimization Design of Concentric Uniform Circular Array Antenna with Improved Array Factor." Applied Computational Electromagnetics Society 36, no. 7 (August 19, 2021): 830–37. http://dx.doi.org/10.47037/2021.aces.j.360702.

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In this paper, an improved array factor of the concentric uniform circular array (CUCA) antenna is proposed for the orbital angular momentum (OAM) vortex beam optimization design. From the perspective of the radiation pattern’s power conservation principle, a correction factor is introduced to the conventional array factor of CUCA. Then, based on the improved array factor, by adjusting the rings’ radii parameters of the CUCA, we optimize the vortex beam’s sidelobe level through the generic algorithm (GA). Two different CUCA antenna model are calculated as examples to further illustrate the effectiveness of the improved array factor. Subsequently, an electromagnetic simulation model of two rings CUCA antenna is built at C band for generating low sidelobe vortex beam carrying OAM mode. The electromagnetic simulation model of the designed CUCA antenna is also fabricated and measured. The corresponding antenna far-field vortex beam radiation pattern and near-field vortex wave electric field distributions are measured. The simulation results and the measurement results are in good agreement. The proposed designs of antenna and OAM vortex beam regulation are expected to be used for 5G and 6G communications applications
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13

Kotlyar, V. V., A. A. Kovalev, E. S. Kozlova, and A. P. Porfirev. "Spiral phase plate with multiple singularity centers." Computer Optics 44, no. 6 (December 2020): 901–8. http://dx.doi.org/10.18287/2412-6179-co-774.

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We investigate a multispiral phase plate (MSPP) with multiple centers of phase singularity arbitrarily located in the MSPP plane. Equations to describe the topological charge of an optical vortex in the initial plane immediately behind the MSPP and orbital angular momentum (OAM) normalized relative to the beam power are derived. The topological charge in the initial plane is found as a sum of the topological charges of all singularities if their centers are located inside a finite-radius circular aperture. If the phase singularity centers are partially located on the boundary of a circular diaphragm limiting the MSPP, the total topological charge is found as the sum of all singularities divided by 2. Total OAM that the vortex carries depends on the location of the singularity centers: the farther from the center of the plate the singularity center is located, the smaller is its contribution to the OAM. If all singularity centers are located on the boundary of the diaphragm limiting MSPP, then the OAM of the vortex beam equals zero, although in this case the topological charge of the beam is nonzero.
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14

Porras, Miguel A. "Effects of the Coupling between the Orbital Angular Momentum and the Temporal Degrees of Freedom in the Most Intense Ring of Ultrafast Vortices." Applied Sciences 10, no. 6 (March 12, 2020): 1957. http://dx.doi.org/10.3390/app10061957.

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It has recently been shown that the temporal and the orbital angular momentum (OAM) degrees of freedom in ultrafast (few-cycle) vortices are coupled. This coupling manifests itself with different effects in different parts of the vortex, as has been shown for the ring surrounding the vortex where the pulse energy is maximum, and also in the immediate vicinity of the vortex center. However, in many applications, the ring of maximum energy is not of primary interest, but the one where the peak intensity of the pulse is maximum, which is particularly true in nonlinear optics applications such as experiments with ultrafast vortices that excite high harmonics and attosecond pulses that also carry OAM. In this paper, the effects of the OAM-temporal coupling on the ring of maximum pulse peak intensity, which do not always coincide with the ring of maximum pulse energy, are described. We find that there is an upper limit to the magnitude of the topological charge that an ultrafast vortex with a prescribed pulse shape in its most intense ring can carry, and vice versa, a lower limit to the pulse duration in the most intense ring for a given magnitude of the topological charge. These limits imply that, with a given laser source spectrum, the duration of the synthesized ultrafast vortex increases with the magnitude of the topological charge. Explicit analytical expressions are given for the ultrafast vortices that contain these OAM-temporal couplings effects, which may be of interest in various applications, in particular in the study of their propagation and interaction with matter.
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15

Wang, Ziyang, Xiaotian Pan, Fan Yang, Shenheng Xu, and Maokun Li. "Real-Time Mode Switching and Beam Scanning of High-Gain OAM Waves Using a 1-Bit Reconfigurable Reflectarray Antenna." Electronics 9, no. 12 (December 18, 2020): 2181. http://dx.doi.org/10.3390/electronics9122181.

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A reconfigurable electromagnetic surface has been studied to realize the adjustable orbital angular momentum (OAM) beams for real-time wireless communication and dynamic target detection in the future. OAM mode switching realized by many previous designs suffers from low gains without OAM beam scanning. In this article, a 1-bit reconfigurable reflectarray antenna is designed, fabricated, and tested for the real-time control of OAM mode switching and large-angle vortex beam scanning in three-dimensional space. The proposed reflectarray surface is composed of 1-bit electronically reconfigurable cells, and the size is 24 λ × 24 λ with 2304 units. The reconfigurable element is designed by using a radiation patch loading a PIN diode with effective control of two states, “ON” and “OFF”, for the demand of 180° phase difference. The reflectarray surface can be assigned to a code sequence of 0 or 1 by the Field-Programmable Gate Array (FPGA) in real time. Henceforth, the coding surface can dynamically control the generation of high-gain OAM beams, where only the optimized phase distributions on the surface need to be changed according to demand. To verify the concept, a large-scale reflectarray surface is fabricated and measured with an oblique feed at 15°. Different OAM-carrying phase distributions for different OAM beam states are calculated and tested. The test results show that the OAM mode switching between l = 1 and l = 2 is realized, and other variable modes such as l = 3 or l = 5 can also be achieved by modifying the phase encoding sequence. Furthermore, the direction of the vortex beams can be accurately controlled with gains over 20 dBi, and the large-angle vortex beam scanning is verified. Therefore, all results demonstrate that the proposed 1-bit reconfigurable reflectarray is efficient for the regulation and control of OAM-carrying beams for the demand of real-time dynamic wireless communications in the future.
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Dedo, Maxime Irene, Zikun Wang, Kai Guo, Yongxuan Sun, Fei Shen, Hongping Zhou, Jun Gao, Rui Sun, Zhizhong Ding, and Zhongyi Guo. "Retrieving Performances of Vortex Beams with GS Algorithm after Transmitting in Different Types of Turbulences." Applied Sciences 9, no. 11 (May 31, 2019): 2269. http://dx.doi.org/10.3390/app9112269.

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The transmission of the orbital angular momentum (OAM) beam has attracted a lot of attention in the field of free-space optical (FSO) communication. Usually, after transmitting in atmospheric turbulences, the helical phase-front of OAM beams will be severely distorted, and there will exist the intermode crosstalk. As a result, the performance of the communication system will degrade significantly. In this paper, we have investigated the influences of the level of the turbulence strength to the transmitting OAM beams by changing the refractive-index structural parameter of C n 2 and the number of turbulence random phase screens of N in simulation environment. Then, by adopting the Gerchberg-Saxton (GS) algorithm, which can be used to compute the pre-compensation phase and correct the distorted OAM beams, the retrieving performances of transmitting single and multiplexed OAM beams under different turbulence strengths were also investigated. The simulation results show that with increasing the atmospheric-turbulence strength levels determined by the parameters C n 2 and N, the retrieving performances decrease dramatically. When the turbulence strength level is selected within an appropriate range, the OAM beams can be effectively retrieved by adopting GS algorithm and observing the power density spectrum. Notably, the retrieving performance for the transmission of a single OAM beam is better than that of the multiplexing OAM beam.
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17

Yang, Yang, Zhanliang Wang, Shaomeng Wang, Qing Zhou, Fei Shen, Haibo Jiang, Zhe Wu, Baoqing Zeng, Zhongyi Guo, and Yubin Gong. "Designing a Water-Immersed Rectangular Horn Antenna for Generating Underwater OAM Waves." Electronics 8, no. 11 (October 26, 2019): 1224. http://dx.doi.org/10.3390/electronics8111224.

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In order to extend the applications of vortex waves, we propose a water-immersed rectangular horn antenna array for generating underwater vortex waves carrying the orbital angular momentum (OAM). Firstly, a single dielectric-loaded rectangular horn antenna with the central frequency of 2.6 GHz was designed for generating underwater electromagnetic (EM) waves. Due to the supplementing dielectric-loaded waveguide in this single antenna, the problems with difficult sealing and fixation of the feed probe could be solved effectively. The simulation results show that it has a good impedance characteristics (S11 < −10 dB) and reasonable losses (less than 3.5 dB total for two antennas and a coaxial line) from 2.5 GHz to 2.7 GHz. Experiments on the single antenna were also carried out, which agree well with the simulations. Based on the designed single antenna, the water-immersed rectangular horn antenna array was proposed, and the phase gradient from 0~2π was fed to the horn antennas for generating underwater OAM waves. The simulation results demonstrate high fidelity of the generated OAM waves from the intensity and phase distributions. The purity of the generated OAM modes was also investigated and further verifies the high fidelity of the generated OAM waves. The generated high-quality OAM waves meet the requirements for underwater applications of OAM, such as underwater communication and underwater imaging.
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18

Su, Mingyang, Junmin Liu, Yanliang He, Shuqing Chen, and Ying Li. "Optical Orbital Angular Momentum Demultiplexing and Channel Equalization by Using Equalizing Dammann Vortex Grating." Advances in Condensed Matter Physics 2017 (2017): 1–9. http://dx.doi.org/10.1155/2017/6293910.

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A novel equalizing Dammann vortex grating (EDVG) is proposed as orbital angular momentum (OAM) multiplexer to realize OAM signal demultiplexing and channel equalization. The EDVG is designed by suppressing odd diffraction orders and adjusting the grating structure. The light intensity of diffraction is subsequently distributed evenly in the diffraction orders, and the total diffraction efficiency can be improved from 53.22% to 82%. By using the EDVG, OAM demultiplexing and channel equalization can be realized. Numerical simulation shows that the bit error rate (BER) of each OAM channel can decrease to 10-4 when the bit SNR is 22 dB, and the intensity is distributed over the necessary order of diffraction evenly.
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Zhang, Yan, Minru Hao, Min Shao, and Yunzhe Zhang. "Propagation Characteristics of Vortex Beam Using Visualization Analysis in Free Space." Journal of Nanoelectronics and Optoelectronics 16, no. 5 (May 1, 2021): 838–43. http://dx.doi.org/10.1166/jno.2021.2990.

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We theoretically analyze the linear momentum density and orbital angular momentum (OAM) propagation characteristics of Gaussian vortex beams in free space, and perform detailed numerical simulation analysis of the linear momentum density and OAM propagation characteristics. Further, we study the variation of the propagation characteristics with different topological charges. In addition, we also analyzed the position of momentum in the transverse profile, where the momentum density of the spot will be broadened with propagation distance. This study can provide guidance for using vortex beams in optical communication and manipulation.
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20

Fu, Yangyang, Chen Shen, Xiaohui Zhu, Junfei Li, Youwen Liu, Steven A. Cummer, and Yadong Xu. "Sound vortex diffraction via topological charge in phase gradient metagratings." Science Advances 6, no. 40 (October 2020): eaba9876. http://dx.doi.org/10.1126/sciadv.aba9876.

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Wave fields with orbital angular momentum (OAM) have been widely investigated in metasurfaces. By engineering acoustic metasurfaces with phase gradient elements, phase twisting is commonly used to obtain acoustic OAM. However, it has limited ability to manipulate sound vortices, and a more powerful mechanism for sound vortex manipulation is strongly desired. Here, we propose the diffraction mechanism to manipulate sound vortices in a cylindrical waveguide with phase gradient metagratings (PGMs). A sound vortex diffraction law is theoretically revealed based on the generalized conservation principle of topological charge. This diffraction law can explain and predict the complicated diffraction phenomena of sound vortices, as confirmed by numerical simulations. To exemplify our findings, we designed and experimentally verified a PGM based on Helmholtz resonators that support asymmetric transmission of sound vortices. Our work provides previously unidentified opportunities for manipulating sound vortices, which can advance more versatile design for OAM-based devices.
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Zhang, Hanqing, Wei Duan, Ting Wei, Chunting Xu, and Wei Hu. "Broadband Multichannel Optical Vortex Generators via Patterned Double-Layer Reverse-Twist Liquid Crystal Polymer." Crystals 10, no. 10 (September 29, 2020): 882. http://dx.doi.org/10.3390/cryst10100882.

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The capacity of an optical communication system can be greatly increased by using separate orbital angular momentum (OAM) modes as independent channels for signal transmission and encryption. At present, a transmissive OAM mode generator compatible with wavelength division multiplexing is being highly pursued. Here, we introduce a specific double-layer reverse-twist configuration into liquid crystal polymer (LCP) to overcome wavelength dependency. With this design, broadband-applicable OAM array generators are proposed and demonstrated. A Damman vortex grating and a Damman q-plate were encoded via photopatterning two subsequent LCP layers adopted with oppositely handed chiral dopants. Rectangular and hexagonal OAM arrays with mode conversion efficiencies exceeding 40.1% and 51.0% in the ranges of 530 to 930 nm, respectively, are presented. This provides a simple and broadband efficient strategy for beam shaping.
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22

Shutova, Mariia, Alexandra A. Zhdanova, and Alexei V. Sokolov. "Detection of mixed OAM states via vortex breakup." Physics Letters A 381, no. 4 (January 2017): 408–12. http://dx.doi.org/10.1016/j.physleta.2016.09.031.

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23

Liu, Hongyan, Yu Wang, Jianqiu Wang, Kang Liu, and Hongqiang Wang. "Electromagnetic Vortex Enhanced Imaging Using Fractional OAM Beams." IEEE Antennas and Wireless Propagation Letters 20, no. 6 (June 2021): 948–52. http://dx.doi.org/10.1109/lawp.2021.3067914.

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24

Zhang, Hao, Xinzhong Li, Haixiang Ma, Miaomiao Tang, Hehe Li, and Yangjian Cai. "Centrosymmetric Optical Vortex." Applied Sciences 9, no. 7 (April 4, 2019): 1429. http://dx.doi.org/10.3390/app9071429.

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We report on a novel optical vortex, named as centrosymmetric optical vortex (CSOV), which is constructed via four conventional optical vortices (OVs) with different topological charges (TCs). The orbital angular momentum (OAM) density satisfies centrosymmetric distribution. Meanwhile, it is confined within a single ring whose radius is determined by the cone angle of an axicon. Furthermore, its magnitude and distribution are modulated by a parameter determined via the TCs of the four OVs, named as phase reconstruction factor. Our work provides a novel detached asymmetric light field, which possesses the potential application in macro-particle manipulation, especially separating cells.
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Devlin, Robert C., Antonio Ambrosio, Noah A. Rubin, J. P. Balthasar Mueller, and Federico Capasso. "Arbitrary spin-to–orbital angular momentum conversion of light." Science 358, no. 6365 (November 2, 2017): 896–901. http://dx.doi.org/10.1126/science.aao5392.

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Optical elements that convert the spin angular momentum (SAM) of light into vortex beams have found applications in classical and quantum optics. These elements—SAM-to–orbital angular momentum (OAM) converters—are based on the geometric phase and only permit the conversion of left- and right-circular polarizations (spin states) into states with opposite OAM. We present a method for converting arbitrary SAM states into total angular momentum states characterized by a superposition of independent OAM. We designed a metasurface that converts left- and right-circular polarizations into states with independent values of OAM and designed another device that performs this operation for elliptically polarized states. These results illustrate a general material-mediated connection between SAM and OAM of light and may find applications in producing complex structured light and in optical communication.
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Kotlyar, V. V., A. A. Kovalev, and A. G. Nalimov. "Astigmatic transformation of a set of edge dislocations embedded in a Gaussian beam." Computer Optics 45, no. 2 (April 2021): 190–99. http://dx.doi.org/10.18287/2412-6179-co-849.

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It is theoretically shown how a Gaussian beam with a finite number of parallel lines of intensity nulls (edge dislocations) is transformed using a cylindrical lens into a vortex beam that carries orbital angular momentum (OAM) and has a topological charge (TC). In the initial plane, this beam already carries OAM, but does not have TC, which appears as the beam propagates further in free space. Using an example of two parallel lines of intensity nulls symmetrically located relative to the origin, we show the dynamics of the formation of two intensity nulls at the double focal length: as the distance between the vertical lines of intensity nulls is being increased, two optical vortices are first formed on the horizontal axis, before converging to the origin and then diverging on the vertical axis. At any distance between the zero-intensity lines, the optical vortex has the topological charge TC=–2, which conserves at any on-axis distance, except the initial plane. When the distance between the zero-intensity lines changes, the OAM that the beam carries also changes. It can be negative, positive, and at a certain distance between the lines of intensity nulls OAM can be equal to zero. It is also shown that for an unlimited number of zero-intensity lines, a beam with finite OAM and an infinite TC is formed.
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27

Kotlyar, V. V., A. A. Kovalev, and E. G. Abramochkin. "Asymmetric hypergeometric laser beams." Computer Optics 43, no. 5 (October 2019): 735–40. http://dx.doi.org/10.18287/2412-6179-2019-43-5-735-740.

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Here we study asymmetric Kummer beams (aK-beams) with their scalar complex amplitude being proportional to the Kummer function (a degenerate hypergeometric function). These beams are an exact solution of the paraxial propagation equation (Schrödinger-type equation) and obtained from the conventional symmetric hypergeometric beams by a complex shift of the transverse coordinates. On propagation, the aK-beams change their intensity weakly and rotate around the optical axis. These beams are an example of vortex laser beams with a fractional orbital angular momentum (OAM), which depends on four parameters: the vortex topological charge, the shift magnitude, the logarithmic axicon parameter and the degree of the radial factor. Changing these parameters, it is possible to control the beam OAM, either continuously increasing or decreasing it.
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28

Wang, Jianqiu, Kang Liu, Yongqiang Cheng, and Hongqiang Wang. "Vortex SAR Imaging Method Based on OAM Beams Design." IEEE Sensors Journal 19, no. 24 (December 15, 2019): 11873–79. http://dx.doi.org/10.1109/jsen.2019.2937976.

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29

Liu, Hongyan, Kang Liu, Yongqiang Cheng, and Hongqiang Wang. "Microwave Vortex Imaging Based on Dual Coupled OAM Beams." IEEE Sensors Journal 20, no. 2 (January 15, 2020): 806–15. http://dx.doi.org/10.1109/jsen.2019.2943698.

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30

Zhang, Di, Xiangyu Cao, Huanhuan Yang, Jun Gao, and Xuewen Zhu. "Multiple OAM vortex beams generation using 1-bit metasurface." Optics Express 26, no. 19 (September 7, 2018): 24804. http://dx.doi.org/10.1364/oe.26.024804.

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31

Wang, Lulu, Huiyong Chen, Kai Guo, Fei Shen, and Zhongyi Guo. "An Inner- and Outer-Fed Dual-Arm Archimedean Spiral Antenna for Generating Multiple Orbital Angular Momentum Modes." Electronics 8, no. 2 (February 22, 2019): 251. http://dx.doi.org/10.3390/electronics8020251.

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Orbital angular momentum (OAM) beams have attracted great attention owing to their excellent performances in imaging and communication. In this paper, a dual-arm Archimedean spiral antenna (DASA) is proposed to generate multiple OAM states with positive and negative values by feeding at the inner and outer ends, respectively. The topological charge of radiated vortex waves is reconfigurable by tuning the operating frequency. Dual-mode OAM states are generated at different working frequencies (l = ±1 at 3 GHz, l = ±2 at 4 GHz, and l = ±3 at 4.8 GHz). Both the simulation and measurement results demonstrate that OAM beams can be generated effectively by the DASA. In addition, a conical cavity is used to increase the gain of the proposed DASA for more than 5 dBi in comparison to the traditional cylindrical cavity. Furthermore, the qualities of the generated OAM modes by the proposed DASA have been evaluated at different operating frequencies of 3 GHz, 4 GHz, and 4.8 GHz, respectively. The OAM modes purities of l = −1, −2, −3, 1, 2, and 3 are predominate with the proportion of about 81%, 70%, 74%, 78%, 77%, and 75%, respectively. Our results demonstrate that the proposed DASA has great potentials in OAM multiplexing communication systems.
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32

Zhang, Chen, Li Deng, Ling Wang, Xue Chen, and Shufang Li. "Generation of Circularly Polarized Quasi-Non-Diffractive Vortex Wave via a Microwave Holographic Metasurface Integrated with a Monopole." Applied Sciences 11, no. 15 (August 2, 2021): 7128. http://dx.doi.org/10.3390/app11157128.

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In this paper, a novel method for generating a circularly polarized (CP) quasi-non-diffractive vortex wave carrying orbital angular momentum (OAM), based on the microwave holographic metasurface integrated with a monopole, is proposed. This method is the combination of the non-diffraction theory and the principle of waveguide-fed-based holography and is equivalent to a superposition of two scalar impedance modulation surfaces. To verify the proposed method, a holographic metasurface generating a left-handed circularly polarized (LHCP) quasi-non-diffractive vortex wave carrying −1 mode OAM at the normal direction, was simulated and analyzed. The metasurface consisted of inhomogeneous slot units on a grounded substrate and a monopole excitation. Moreover, the location distribution of slots was determined by a computed interferogram between the reference wave and the object wave with the non-diffractive feature. Compared with an ordinary vortex wave, the quasi-non-diffractive wave obtained by our proposed method possessed a smaller divergence radius and a stronger electric field strength in the 9 times wavelength range. It paved a new path for manipulating the non-diffractive vortex wave in medium distance without using an external feeding source, which holds great potential for the miniaturization devices applied in medium-distance high-capacity secure communication, high-resolution imaging and intelligent detection.
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33

Mao, Pengrong, and Canguan Gao. "Design of a Multimode OAM Vortex Electromagnetic Microstrip Array Antenna." Journal of Physics: Conference Series 1549 (June 2020): 042127. http://dx.doi.org/10.1088/1742-6596/1549/4/042127.

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34

Lee, Song, and Kim. "Analysis of Bending-Induced Degradation of Orbital Angular Momentum Modes in Optical Fibers." Photonics 6, no. 3 (September 1, 2019): 97. http://dx.doi.org/10.3390/photonics6030097.

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In this work, bending-induced deterioration of orbital angular momentum (OAM) modes in ring core fiber (RCF), photonic crystal fiber (PCF), and vortex fiber (VF) was theoretically investigated: Bending losses, coupling losses, and intermodal crosstalk at the interface between straight and bent optical fibers were investigated from the modal analysis of those three types of OAM mode fibers. In addition, the degradation of a topological charge number of an OAM mode due to the bending-induced birefringence and horizontal mode asymmetry was also investigated. Our investigation revealed that, in all aspects, the PCF is most robust to bending among the three types of optical fibers, and the most serious bending-induced problem in the VF and the RCF is the degradation of the topological charge number. The allowed minimum bending radii of VF and RCF appeared to be ~15 and ~45 mm, respectively, for the specific structures considered in this work. We expect that the methodology and results of our quantitative analysis on bending-induced degradation of OAM modes will be of great use in the design of OAM mode fibers for practical use.
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35

Kovalev, A. A., and A. P. Porfirev. "Birth of optical vortices in propagating fields with an original fractional topological charge." Computer Optics 44, no. 4 (August 2020): 493–500. http://dx.doi.org/10.18287/2412-6179-co-715.

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In contrast to the orbital angular momentum (OAM), which is conserved on free space propagation, the topological charge (TC) of a paraxial optical vortex (OV) is not conserved in the general case. Here, we investigate a Gaussian beam with a fractional TC in the original plane and demonstrate both theoretically and numerically how the TC changes in the course of propagation. Depending on the proximity of the topological charge to an even or odd integer number, an optical vortex with the original fractional TC is shown to behave in a number of different ways. For simple OVs (Laguerre-Gaussian or Bessel-Gaussian modes), TC is conserved both in propagation and after weak phase distortions. An experiment shows that when scattered by a random phase screen, the integer TC of an OV is conserved right up to a random phase variation of π. Therefore, in the case of weak turbulences, it is expedient to measure a discretely varying TC instead of a continuously varying OAM.
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36

Gizatulin, Azat R. "Generation of optical signals carrying OAM based on vortex fiber-optic periodic structures." Physics of Wave Processes and Radio Systems 23, no. 3 (December 27, 2020): 18–26. http://dx.doi.org/10.18469/1810-3189.2020.23.3.18-26.

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In this article, author considers the process of generation of fiber modes carrying orbital angular momentum (vortex modes) using chiral fiber Bragg gratings; in this context, the formation of vortex modes is carried out by converting thefundamental mode into higher order modes. Within the framework of the article, a generalized mathematical model of chiral fiber Bragg gratings is presented, which includes an arbitrary function of apodization and chirping, which makes it possible to calculate gratings that form vortex modes of a given order for the required frequency range with the required reflection coefficient. In addition, a matrix method for describing chiral fiber Bragg gratings is proposed, based on the mathematical apparatus of the coupled modes theory and scattering matrices. This matrix approach is convenient for describing complex and / or cascaded gratings. In addition, in this work, simulation of the considered fiber structures is carried out.
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37

KIM, Teun-Teun. "Spin-Orbital Angular Momentum of Light and Its Application." Physics and High Technology 29, no. 10 (October 31, 2020): 28–31. http://dx.doi.org/10.3938/phit.29.037.

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Like the eletron, the photon carries spin and orbital angular momentum caused by the polarization and the spatial phase distribution of light, respectively. Since the first observation of an optical vortex beam with orbital angular momentum (OAM), the use of an optical vortex beam has led to further studies on the light-matter interaction, the quantum nature of light, and a number of applications. In this article, using a metasurface with geometrical phase, we introduce the fundamental origins and some important applications of light with spin-orbit angular momentum as examples, including optical vortex tweezer and quantum entanglement of the spin-orbital angular momentum.
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38

Ma, Qian, and Hengkai Zhao. "Capacity of a Radio Vortex Communication System Using a Partial Angular Aperture Receiving Scheme under the Horizontal Non-Kolmogorov Model." Sensors 21, no. 5 (March 4, 2021): 1778. http://dx.doi.org/10.3390/s21051778.

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A partial receiving scheme based on limited angular aperture multi-beam receiving and demultiplexing can solve the difficulty caused by the divergence of the vortex beam in the conventional whole beam receiving scheme and realize the long-distance transmission of the vortex wave. The propagation of the radio vortex beam in atmospheric turbulence is of significant importance in theoretical study and practical applications. In this paper, the influence of atmospheric turbulence on the performance of a radio vortex (RV) communication system based on a partial angular aperture receiving (PAAR) scheme under the horizontal non-Kolmogorov channel model is studied. The spiral spectrum of the PAAR scheme and the channel capacity of the RV communication system using the PAAR scheme are derived. Simulation results demonstrate that the selected transmission frequency range has a great influence on the RV communication system based on the PAAR scheme, and the choice of the orbital angular momentum (OAM) mode number L has an influence on the propagation distance. The capacity of RV communication systems based on the PAAR scheme increases with the increase of the transmission frequency in the selected transmission frequency range of 10 GHz–60 GHz. When the number of orbital angular momentum (OAM) modes L is small, we can improve the signal-to-noise ratio (SNR) to obtain a larger capacity of the RV communication system based on the PAAR scheme over a longer propagation distance.
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39

Wang, Sha, Shu-lin Zhang, Ping Li, Mei-hui Hao, Huo-mu Yang, Jian Xie, Guo-ying Feng, and Shou-huan Zhou. "Generation of wavelength- and OAM-tunable vortex beam at low threshold." Optics Express 26, no. 14 (June 28, 2018): 18164. http://dx.doi.org/10.1364/oe.26.018164.

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40

Zhang, Di, Xiangyu Cao, Huanhuan Yang, and Jun Gao. "Radiation Performance Synthesis for OAM Vortex Wave Generated by Reflective Metasurface." IEEE Access 6 (2018): 28691–701. http://dx.doi.org/10.1109/access.2018.2839099.

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41

Sun, Changzheng, Juan Zhang, Bing Xiong, Jian Wang, Zhibiao Hao, Lai Wang, Yanjun Han, Hongtao Li, and Yi Luo. "Analysis of OAM Mode Purity of Integrated Optical Vortex Beam Emitters." IEEE Photonics Journal 9, no. 1 (February 2017): 1–7. http://dx.doi.org/10.1109/jphot.2017.2652722.

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42

Guo, Shaoqing, Zi He, Zhenhong Fan, and Rushan Chen. "CUCA Based Equivalent Fractional Order OAM Mode for Electromagnetic Vortex Imaging." IEEE Access 8 (2020): 91070–75. http://dx.doi.org/10.1109/access.2020.2995149.

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43

Kotlyar, Victor V., and Alexey A. Kovalev. "Optical vortex beams with a symmetric and almost symmetric OAM spectrum." Journal of the Optical Society of America A 38, no. 9 (August 16, 2021): 1276. http://dx.doi.org/10.1364/josaa.432623.

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44

Abhyankar, Girish G., R. S. Gad, Charanarur Panem, Deepak Chodankar, and G. M. Naik. "Gaussian vortex beam modeling for multiplexing in data communication using OAM." Journal of Physics: Conference Series 1921 (May 2021): 012054. http://dx.doi.org/10.1088/1742-6596/1921/1/012054.

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45

Qin, Fan, Rui Song, Wenchi Cheng, and Hailin Zhang. "Multibeam OAM Transmitarray With Stable Vortex Property Based on Bifocal Method." IEEE Antennas and Wireless Propagation Letters 20, no. 9 (September 2021): 1601–5. http://dx.doi.org/10.1109/lawp.2021.3084604.

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46

Hu, Tao, Yang Wang, Bo Ma, and Jie Zhang. "Orbit Angular Momentum MIMO with Mode Selection for UAV-Assisted A2G Networks." Sensors 20, no. 8 (April 17, 2020): 2289. http://dx.doi.org/10.3390/s20082289.

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As an emerging solution for line-of-sight (LOS) wireless communications, in air-to-ground (A2G) channels, the unmanned aerial vehicle (UAV), and allowing the dynamic and flexible network deployments enables the supplement or/and replacement of the terrestrial base stations (BSs). However, in conventional multiple-input-multiple-output (MIMO) systems, high-speed communications are significantly limited by channel crosstalks and spectrum scarcities. An orbit angular momentum (OAM) wireless network, allowing co-existence of multiple physical channels within the same frequency band, offers new degrees of freedom to address this dilemma. In this paper, we investigate the UAV-based A2G radio vortex wireless networks and study its channel model. Then we propose a branch and bound search-based mode selection (BBS-MS) scheme, which uses the spatial distribution characteristics of vortex beams to optimize the spectrum efficiency (SE). Theoretical derivations and numerical results demonstrate that our developed BBS-MS scheme can obtain the optimal performance, which outperforms conventional OAM-based MIMO systems. Also, it possesses a lower complexity compared with exhaustive searches.
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47

Liu, Zhirong, Kelin Huang, Anlian Yang, Xun Wang, and Philip H. Jones. "Strongly Focused Circularly Polarized Optical Vortices Regulated by a Fractal Conical Lens." Applied Sciences 10, no. 1 (December 18, 2019): 28. http://dx.doi.org/10.3390/app10010028.

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In this paper, a recently-proposed pure-phase optical element, the fractal conical lens (FCL), is introduced for the regulation of strongly-focused circularly-polarized optical vortices in a high numerical aperture (NA) optical system. Strong focusing characteristics of circularly polarized optical vortices through a high NA system in cases with and without a FCL are investigated comparatively. Moreover, the conversion between spin angular momentum (SAM) and orbital angular momentum (OAM) of the focused optical vortex in the focal vicinity is also analyzed. Results revealed that a FCL of different stage S could significantly regulate the distributions of tight focusing intensity and angular momentum of the circularly polarized optical vortex. The interesting results obtained here may be advantageous when using a FCL to shape vortex beams or utilizing circularly polarized vortex beams to exploit new-type optical tweezers.
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48

Knyazev, Boris, Valery Cherkassky, and Oleg Kameshkov. "“Perfect” Terahertz Vortex Beams Formed Using Diffractive Axicons and Prospects for Excitation of Vortex Surface Plasmon Polaritons." Applied Sciences 11, no. 2 (January 13, 2021): 717. http://dx.doi.org/10.3390/app11020717.

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Transformation of a Bessel beam by a lens results in the formation of a “perfect” vortex beam (PVB) in the focal plane of the lens. The PVB has a single-ring cross-section and carries an orbital angular momentum (OAM) equal to the OAM of the “parent” beam. PVBs have numerous applications based on the assumption of their ideal ring-type structure. For instance, we proposed using terahertz PVBs to excite vortex surface plasmon polaritons propagating along cylindrical conductors and the creation of plasmon multiplex communication lines in the future (Comput. Opt. 2019, 43, 992). Recently, we demonstrated the formation of PVBs in the terahertz range using a Bessel beam produced using a spiral binary silicon axicon (Phys. Rev. A 2017, 96, 023846). It was shown that, in that case, the PVB was not annular, but was split into nested spiral segments, which was obviously a consequence of the method of Bessel beam generation. The search for methods of producing perfect beams with characteristics approaching theoretically possible ones is a topical task. Since for the terahertz range, there are no devices like spatial modulators of light in the visible range, the main method for controlling the mode composition of beams is the use of diffractive optical elements. In this work, we investigated the characteristics of perfect beams, the parent beams being quasi-Bessel beams created by three types of diffractive phase axicons made of high-resistivity silicon: binary, kinoform, and “holographic”. The amplitude-phase distributions of the field in real perfect beams were calculated numerically in the approximation of the scalar diffraction theory. An analytical expression was obtained for the case of the binary axicon. It was shown that a distribution closest to an ideal vortex was obtained using a holographic axicon. The resulting distributions were compared with experimental and theoretical distributions of the evanescent field of a plasmon near the gold–zinc sulfide–air surface at different thicknesses of the dielectric layer, and recommendations for experiments were given.
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49

Shi, Chengzhi, Marc Dubois, Yuan Wang, and Xiang Zhang. "High-speed acoustic communication by multiplexing orbital angular momentum." Proceedings of the National Academy of Sciences 114, no. 28 (June 26, 2017): 7250–53. http://dx.doi.org/10.1073/pnas.1704450114.

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Long-range acoustic communication is crucial to underwater applications such as collection of scientific data from benthic stations, ocean geology, and remote control of off-shore industrial activities. However, the transmission rate of acoustic communication is always limited by the narrow-frequency bandwidth of the acoustic waves because of the large attenuation for high-frequency sound in water. Here, we demonstrate a high-throughput communication approach using the orbital angular momentum (OAM) of acoustic vortex beams with one order enhancement of the data transmission rate at a single frequency. The topological charges of OAM provide intrinsically orthogonal channels, offering a unique ability to multiplex data transmission within a single acoustic beam generated by a transducer array, drastically increasing the information channels and capacity of acoustic communication. A high spectral efficiency of 8.0 ± 0.4 (bit/s)/Hz in acoustic communication has been achieved using topological charges between −4 and +4 without applying other communication modulation techniques. Such OAM is a completely independent degree of freedom which can be readily integrated with other state-of-the-art communication modulation techniques like quadrature amplitude modulation (QAM) and phase-shift keying (PSK). Information multiplexing through OAM opens a dimension for acoustic communication, providing a data transmission rate that is critical for underwater applications.
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Gao, Hui, Yang Li, Lianwei Chen, Jinjin Jin, Mingbo Pu, Xiong Li, Ping Gao, Changtao Wang, Xiangang Luo, and Minghui Hong. "Quasi-Talbot effect of orbital angular momentum beams for generation of optical vortex arrays by multiplexing metasurface design." Nanoscale 10, no. 2 (2018): 666–71. http://dx.doi.org/10.1039/c7nr07873k.

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The quasi-Talbot effect of orbital angular momentum (OAM) beams, in which the centers are placed in a rotationally symmetric position, is demonstrated both numerically and experimentally for the first time.
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