Orbital Angular Momentum Multiplexing Research Articles

E‐Band Metasurface‐Based Orbital Angular Momentum Multiplexing and Demultiplexing

AbstractOrbital angular momentum (OAM) has received considerable attention regarding high‐capacity communication owing to its spatial orthogonality. However, it is still challenging to build a compact communication system that can generate multiple coaxial OAM beams and receive information from each. In this work, OAM multiplexing and demultiplexing at the E‐band frequency using a single metasurface structure is proposed and experimentally demonstrated. For OAM multiplexing, the metasurface used as a transceiver generates two orthogonal coaxial OAM beams for Gaussian incident beams with different incidence angles. For OAM demultiplexing, the same metasurface flipped 180° as a receiver forms a Gaussian beam in different off‐axis directions depending on the topological charge of the coaxially incident OAM beam. The Gaussian beam measured at the receiver end exhibits a high signal‐to‐noise ratio of more than 33 dB compared with the background OAM beam. OAM multiplexing and demultiplexing based on a single metasurface may provide a route for high‐capacity and compact free‐space communication systems.

Security enhancement for adaptive optics aided longitudinal orbital angular momentum multiplexed underwater wireless communications.

The frozen-wave-based longitudinal orbital angular momentum multiplexing (LOAMM) system developed in [IEEE Photonics J.10, 7900416 (2018)10.1109/JPHOT.2017.2778238] has the potential to overcome the crosstalk effects induced by turbulence. In this paper, we propose a defocus measurement aided adaptive optics (DMA-AO) technique for turbulence compensation in a LOAMM underwater wireless optical communication (UWOC) system to investigate the enhancement of physical layer security. Relying on a phase retrieval algorithm and probe beam, three amplitude-only measurements obtained from different back focus planes can realize phase reconstruction of distorted OAM beams. Moreover, the so-called mixture generalized gamma-Johnson SB (GJSB) distribution is proposed to characterize the probability density function (PDF) of reference-channel irradiance of OAM. The GJSB allows for obtaining closed-form and analytically tractable expression for the probability of strictly positive secrecy capacity (SPSC) in a single input single output (SISO) system. Furthermore, the average secrecy capacity (ASC) and probability of SPSC for a multiple input multiple output (MIMO) system are investigated. Compared to the traditional OAM multiplexing system based on Laguerre-Gaussian (LG) beams, the LOAMM system with a probe beam assisted DMA-AO technique has potential advantages for improving the security performance in UWOC.

Multi-Orbital-Angular-Momentum-Mode Vortex Wave Multiplexing and Demultiplexing with Shared-Aperture Reflective Metasurfaces

As an alternative degree of freedom for wireless communications, orbital angular momentum (OAM) multiplexing and demultiplexing can be applied to achieve higher communication capacity. Metasurface has advanced ability to manipulate electromagnetic (EM) waves, and has gradually become an enabling EM technology for future wireless communications. It is meaningful and useful to combine the advantages of OAM and metasurfaces. Here we propose a multi-OAM-mode vortex wave multiplexing and demultiplexing scheme based on shared-aperture reflective metasurface. The specifically designed reflective metasurface can realize the corresponding OAM-mode modulations and demodulations of different incident carrier waves in the corresponding data channels. By modulating multiple data channels on multiple OAM modes, the multiplication of the communication capacity could be achieved. A prototype operating at microwave frequencies is designed, simulated, and fabricated for proof-of-concept illustration. To validate the OAM multiplexing and demultiplexing scheme, we conduct dual-channel OAM-mode transmission experiments, in which two shared-aperture reflective metasurfaces are adopted as the transmitter and receiver, respectively. This work paves the way for the metasurface-based OAM communication applications in future wireless communication technologies.

Deterministic distribution of orbital angular momentum multiplexed continuous-variable entanglement and quantum steering

Orbital angular momentum (OAM) multiplexing provides an efficient method to improve data-carrying capacity in various quantum communication protocols. It is a precondition to distribute OAM multiplexed quantum resources in quantum channels for implementing quantum communication. However, quantum steering of OAM multiplexed optical fields and the effect of channel noise on OAM multiplexed quantum resources remain unclear. Here, we generate OAM multiplexed continuous-variable (CV) entangled states and distribute them in lossy or noisy channels. We show that the decoherence property of entanglement and quantum steering of the OAM multiplexed states carrying topological charges l = 1 and l = 2 are the same as that of the Gaussian mode with l = 0 in lossy and noisy channels. The sudden death of entanglement and quantum steering of high-order OAM multiplexed states is observed in the presence of excess noise. Our results demonstrate the feasibility to realize high data-carrying capacity quantum information processing by utilizing OAM multiplexed CV entangled states.

Experimental Evaluation of High-capacity Wireless Transmission Using Orbital Angular Momentum Multiplexing Technology

Experimental Evaluation of High-capacity Wireless Transmission Using Orbital Angular Momentum Multiplexing Technology

Generation and conversion of a dual-band Laguerre-Gaussian beam with different OAM based on a bilayer metasurface

In this paper, we propose a bilayer metasurface with dual-operating modes to realize the generation and conversion of dual-band Laguerre-Gaussian beam with different OAM. The bilayer metasurface consists of amorphous silicon (a-Si) and amorphous antimony selenide (a-Sb2Se3). In transmission mode, the metasurface can transform incident left-handed circularly polarized (LCP) Gaussian beam into one LCP Laguerre-Gaussian beam carrying topological charge l=−2 and one right-handed circularly polarized (RCP) Laguerre-Gaussian beam carrying topological charge l=−1, which enabled OAM modes multiplexing. In reflection mode, the metasurface can convert an incident LCP Gaussian beam into a LCP Laguerre-Gaussian beam carrying a topological charge l=−3 owing to the a-Sb2Se3 nanopillar that acts as a half-wave plate with high reflectivity. In addition, the OAM conversion between two arbitrary modes can be realized by the proposed metasurface. This work provides a valid method for OAM multiplexing and conversion, which holds a great applications value in high-speed optical communication systems.

Dynamic millimeter-wave OAM beam generation through programmable metasurface

Abstract Millimeter-wave (mmWave) and orbital angular momentum (OAM) multiplexing are two key technologies for modern wireless communications, where significant efforts have been devoted to combining these two technologies for extremely high channel capacities. Recently, programmable metasurfaces have been extensively studied for stimulating dynamic multi-mode OAM beams, owing to their ability of subtle dynamic modulation over electromagnetic waves in a digital manner. However, programmable metasurfaces for mmWave OAM stimulation are rarely mentioned, due to the requirement of extremely high processing precision for mmWave applications. In this paper, a programmable metasurface is presented to stimulate dynamic multi-mode mmWave vortex beams. The proposed metasurface is composed of electronically reconfigurable units, which is obtained through configuration integration of a PIN diode within each radiation patch for modulating the unit resonant property. Both low reflection losses and stabilized inverse phase states are obtained for the binary unit coding states within the operation band. Through modulating the real-time coding distribution on the metasurface by programmable bias circuit, the generation of mmWave OAM beams with mode numbers l = 0, l = +1, l = +2, and l = +3 are numerically designed and experimentally verified. Our study paves a new perspective for the cross amalgamation of both mmWave and multi-mode OAM technologies.

Corrections to “Millimeter-Wave Holographic Flat Lens Antenna for Orbital Angular Momentum Multiplexing” [Aug 21 4289-4303

Corrections to “Millimeter-Wave Holographic Flat Lens Antenna for Orbital Angular Momentum Multiplexing” [Aug 21 4289-4303

Wireless Communication Utilizing Berry‐Phase Carriers

AbstractOptical and microwave communication classically focus more on the magnitude manipulation of electromagnetic carriers. Recently, a multiplexing method utilizing orbital angular momentum (OAM) is developed, which has been an important study of communication art. Based on OAM multiplexing, a communication method that introduces Berry‐phase carriers is presented in this research, which can naturally eliminate the channel disturbance. To verify the proposed method, two information systems are presented, including a multiplexing communication system in a large‐scale scenario and a double‐helical information system in a microscale scenario. All the results are verified by the corresponding experiments. This method achieves some advanced performances, for instance, directional communication and self‐anti‐interference, which shows potential applications in areas such as information, materials, and bionics.

Optical metasurfaces for generating and manipulating optical vortex beams

Abstract Optical vortices (OVs) carrying orbital angular momentum (OAM) have attracted considerable interest in the field of optics and photonics owing to their peculiar optical features and extra degree of freedom for carrying information. Although there have been significant efforts to realize OVs using conventional optics, it is limited by large volume, high cost, and lack of design flexibility. Optical metasurfaces have recently attracted tremendous interest due to their unprecedented capability in the manipulation of the amplitude, phase, polarization, and frequency of light at a subwavelength scale. Optical metasurfaces have revolutionized design concepts in photonics, providing a new platform to develop ultrathin optical devices for the realization of OVs at subwavelength resolution. In this article, we will review the recent progress in optical metasurface-based OVs. We provide a comprehensive discussion on the optical manipulation of OVs, including OAM superposition, OAM sorting, OAM multiplexing, OAM holography, and nonlinear metasurfaces for OAM generation and manipulation. The rapid development of metasurface for OVs generation and manipulation will play an important role in many relevant research fields. We expect that metasurface will fuel the continuous progress of wearable and portable consumer electronics and optics where low-cost and miniaturized OAM related systems are in high demand.

Millimeter-Wave and Terahertz OAM Discrete-Lens Antennas for 5G and Beyond

The incoming 5G and beyond 5G wireless communications provide unprecedented ultra-high-speed transmission data rates. This is enabled by driving the carrier frequency up to millimeter-wave (mmWave) and terahertz (THz) bands and developing advanced multiplexing technology to increase spectrum bandwidth and spectral efficiency. In this article, we present novel discrete lens antenna designs to solve the two leading open challenges of orbital angular momentum (OAM) applications in mmWave and THz bands: OAM multiplexing and the diffractive problem of OAM waves. For discrete lens antennas operating at THz frequencies, the emerging 3D printing technology and its superior geometric flexibility are utilized to design and implement OAM antennas. The successful demonstration of the mmWave and THz OAM discrete lens antennas can open avenues for future several-hundred-gigabits-per-second wireless communications.

Optical multiplexing techniques and their marriage for on-chip and optical fiber communication: a review

Herein, an attention-grabbing and up-to-date review related to major multiplexing techniques is presented which includes wavelength division multiplexing (WDM), polarization division multiplexing (PDM), space division multiplexing (SDM), mode division multiplexing (MDM) and orbital angular momentum multiplexing (OAMM). Multiplexing is a mechanism by which multiple signals are combined into a shared channel used to showcase the maximum capacity of the optical links. However, it is critical to develop hybrid multiplexing methods to allow enhanced channel numbers. In this review, we have also included hybrid multiplexing techniques such as WDM-PDM, WDM-MDM and PDM-MDM. It is probable to attain <italic>N</italic>×<italic>M</italic> channels by utilizing <italic>N</italic> wavelengths and <italic>M</italic> guided-modes by simply utilizing hybrid WDM-MDM (de)multiplexers. To the best of our knowledge, this review paper is one of its kind which has highlighted the most prominent and recent signs of progress in multiplexing techniques in one place.

Prototyping of 40 GHz Band Orbital Angular Momentum Multiplexing System and Evaluation of Field Wireless Transmission Experiments

We are developing a spatial multiplexing technique based on orbital angular momentum (OAM) that is capable of 1 Tbit/s point-to-point wireless transmissions for the sixth generation mobile communication system. In this paper, we describe a demonstration of 100 Gbit/s wireless transmission over a range of 100 m that used OAM multiplexing of 15 streams with a 1.5 GHz bandwidth (39-41.5 GHz). The OAM modes of this system were generated using a Butler matrix that allows discrete Fourier transform (DFT) operations to be performed in analog circuits. We designed 8×8 Butler matrices to generate OAM modes by combining hybrid couplers and phase shifters. Since this Butler matrix was connected to 16 element antennas, two 8×8 Butler matrices were connected to make an 8×16 matrix. Furthermore, since these inputs were in 7 OAM mode, one port was terminated to create a 7×16 Butler matrix. It was confirmed that the mode isolation was more than 15 dB in the 1.5 GHz bandwidth. Next, we designed microstrip antennas for a horizontal and vertical polarization uniform circular array (UCA) to radiate the OAM modes. Then, we implemented radio frequency (RF) chains and digital signal processing, including single carrier-frequency domain equalization and adaptive modulation and coding. A transmission experiment conducted in a field line-of-sight environment showed that the system could transmit at 119.45 Gbit/s at a distance of 100 meters, thereby demonstrating the feasibility of wideband OAM transmission in the millimeter-wave band.

Multichannel Orbital Angular Momentum Multiplexing with Frequency Selection and Polarization Dependence in the Terahertz Band

Multichannel Orbital Angular Momentum Multiplexing with Frequency Selection and Polarization Dependence in the Terahertz Band

Approaching the Fundamental Limit of Orbital-Angular-Momentum Multiplexing Through a Hologram Metasurface

Establishing and approaching the fundamental limit of orbital angular momentum (OAM) multiplexing are necessary and increasingly urgent for current multiple-input multiple-output research. In this work, we elaborate the fundamental limit in terms of independent scattering channels (or degrees of freedom of scattered fields) through angular-spectral analysis, in conjunction with a rigorous Green function method. The scattering channel limit is universal for arbitrary spatial mode multiplexing, which is launched by a planar electromagnetic device, such as antenna, metasurface, etc, with a predefined physical size. As a proof of concept, we demonstrate both theoretically and experimentally the limit by a metasurface hologram that transforms orthogonal OAM modes to plane-wave modes scattered at critically separated angular-spectral regions. Particularly, a minimax optimization algorithm is applied to suppress angular spectrum aliasing, achieving good performances in both full-wave simulation and experimental measurement at microwave frequencies. This work offers a theoretical upper bound and corresponding approach route for engineering designs of OAM multiplexing.

Orbital angular momentum and beyond in free-space optical communications

AbstractOrbital angular momentum (OAM), which describes tailoring the spatial physical dimension of light waves into a helical phase structure, has given rise to many applications in optical manipulation, microscopy, imaging, metrology, sensing, quantum science, and optical communications. Light beams carrying OAM feature two distinct characteristics, i.e., inherent orthogonality and unbounded states in principle, which are suitable for capacity scaling of optical communications. In this paper, we give an overview of OAM and beyond in free-space optical communications. The fundamentals of OAM, concept of optical communications using OAM, OAM modulation (OAM modulation based on spatial light modulator, high-speed OAM modulation, spatial array modulation), OAM multiplexing (spectrally efficient, high capacity, long distance), OAM multicasting (adaptive multicasting,N-dimensional multicasting), OAM communications in turbulence (adaptive optics, digital signal processing, auto-alignment system), structured light communications beyond OAM (Bessel beams, Airy beams, vector beams), diverse and robust communications using OAM and beyond (multiple scenes, turbulence-resilient communications, intelligent communications) are comprehensively reviewed. The prospects and challenges of optical communications using OAM and beyond are also discussed at the end. In the future, there will be more opportunities in exploiting extensive advanced applications from OAM beams to more general structured light.

Prototype system for underwater wireless optical communications employing orbital angular momentum multiplexing

The orbital angular momentum (OAM) multiplexing technology is an essential method to boost underwater wireless optical communication (UWOC) capacity. However, state-of-art UWOC systems are often demonstrated in the laboratory using bulky and high power-consumption instruments, which can be impractical in a realistic environment. In this work, we propose, design and demonstrate a compact and energy-efficient OAM multiplexing UWOC prototype with complete packaging. Indeed, we improve the signal generation, modulation, receiving and processing components by employing the integrated programmable chips. We also employ two geometric phase Q-plate chips as an OAM multiplexer and de-multiplexer, respectively. Owing to the improvement of these components and the optical design, we package the complete UWOC system in two 65cm×35cm×40cm boxes with the power consumption of 20W. Our experiment demonstrates such a completely packaged prototype can support two 625Mbit/s channels (OAM+3, OAM-3) multiplexing in a 6-meter underwater environment with fidelity.

Synthetic helical dichroism for six-dimensional optical orbital angular momentum multiplexing

Synthetic helical dichroism for six-dimensional optical orbital angular momentum multiplexing

Metasurface Based Optical Orbital Angular Momentum Multiplexing for 100 GHz Radio Over Fiber Communication

Optical vortex beams (VBs) carrying orbital angular momentum (OAM) have shown significant multiplexing ability in radio-over-fiber communication by virtue of their intrinsic mode orthogonality. However, the large bandwidth required by optical microwave and the narrow bandwidth of mode converters severely hinder its practical applications. By exploiting the Pancharatnam-Berry phase of metasurface, we experimentally demonstrate a mode conversion solution for OAM multiplexing based radio-over-fiber communication. Based on the dispersion-free Pancharatnam-Berry phase design, these metasurfaces show broadband working wavelengths (from 1540 nm to 1600 nm) and polarization-insensitive characteristic. These make them compatible with polarization division multiplexing (PDM) and wavelength division multiplexing (WDM). As a proof-on-concept, a three-dimensional multiplexing based radio-over-fiber communication is demonstrated with 2 OAM modes, 2 polarization states and 4 wavelengths, and these 16 channels are demultiplexed with crosstalk less than −13.29 dB. The communication sensitivity decreases about 2.5 dB after introducing PDM and WDM because of the increased crosstalk. The 96 Gbit/s QPSK-OFDM signals carried by 16 channels are demodulated with bit-error-rate lower than 3.26 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−5</sup> at 4.5 dBm.

High-Rate Continuous-Variable Quantum Key Distribution with Orbital Angular Momentum Multiplexing.

The secret key rate is one of the main obstacles to the practical application of continuous-variable quantum key distribution (CVQKD). In this paper, we propose a multiplexing scheme to increase the secret key rate of the CVQKD system with orbital angular momentum (OAM). The propagation characteristics of a typical vortex beam, involving the Laguerre–Gaussian (LG) beam, are analyzed in an atmospheric channel for the Kolmogorov turbulence model. Discrete modulation is utilized to extend the maximal transmission distance. We show the effect of the transmittance of the beam over the turbulent channel on the secret key rate and the transmission distance. Numerical simulations indicate that the OAM multiplexing scheme can improve the performance of the CVQKD system and hence has potential use for practical high-rate quantum communications.