Linear Polarization Modes Research Articles

A quad-polarization reconfigurable transmitarray antenna with beam-scanning and reconfigurable polarization capabilities

Abstract In this paper, a novel quad-polarized electronically reconfigurable transmitarray antenna(QRTA) is proposed, which can actively switch among four linear-polarization modes and steer beam-scanning in these polarization modes. The QRTA element follows a receiving-transmitting structure. Its receiver or transmitter is composed of four rotationally symmetric patches and a coupling patch. Four rotationally symmetric patches generate x- and y-polarization modes, while coupling patches on the top and bottom layers of the QRTA element are designed to synthesize x-, 45◦-, y-, and 135◦-polarization modes. The QRTA element utilizes a reverse symmetry current method to achieve a 180◦ phase difference in the radiated electromagnetic waves. By manipulating the state of the p-i-n diodes, the proposed QRTA element can achieve four LP functions and a 1-bit phase shift. Based on the proposed novel QRTA element, a 10 × 10 elements QRTA prototype is fabricated and measured. The measured results demonstrate that the proposed QRTA can electronically switch between four LP modes and achieve beam-scanning in those LP modes. The proposed QRTA shows several advantages, including low cost, multi-polarization capability, high gain, and beam-scanning, which means that it can enhance the polarization capabilities and intelligence of wireless communication systems.

Halide Perovskite Thin Film Lasing Mode Control.

Metal halide perovskite semiconductors have emerged as highly efficient amplifying materials; to ensure practical applicability, it is important to have precise control over the spectral and polarization characteristics of lasing emission. In this study, we present effective strategies for manipulating single- and multimode lasing from surface-emitting and optically pumped perovskite distributed feedback lasers. We show that cladding structures can be made to modify the optical properties of guided transverse electric and magnetic modes within the gain medium. This leads to spectral tuning of multipeak lasing emission and the generation of linear polarization modes. Our results are supported with a comprehensive multilayer slab waveguide model and confirmed with two different perovskite materials: methylammonium lead iodide and cesium lead bromide.

LP-mode diversity method for the beating model of FM-EDFAs with comparison between different beat lengths

The mode beating effects can be considered for improving the modeling accuracy of few-mode erbium-doped fiber amplifiers (FM-EDFAs). A linearly polarized (LP) mode diversity method for the beating model of FM-EDFAs is proposed in the paper, in which each vector mode is always decomposed into the x- and y-polarized LP components in erbium-doped fibers and then the mode interference effects between the co-polarized LP modes associated with different vector modes act on the erbium-ion population profile. The power evolution of mode as an example is firstly analyzed for three cases of long, moderate and short beat lengths, in comparison with the intensity model. It is shown that the FM-EDFA with a moderate beat length has a potential advantage in gain control and the intensity model is equivalent to the case with the long beat length. The simultaneous amplification of and modes are then investigated for the moderate beat lengths and the modal gain can approximately be expressed by that of the intensity model and a cosine function of the beat length. The similar analysis process is also applied to other beating scenarios, such as the simultaneous amplification of , and modes.

Modal gain characteristics of few-mode erbium-doped fiber amplifiers with pump mode beating

Using the linear polarization (LP) mode decomposition method, we theoretically analyze the beat effect between the same polarization components of the vector pump modes and propose a pump beat model of few-mode erbium-doped fiber amplifiers (FM-EDFAs). The relationship of the overlap factor with the signal gain in the beat model is verified by the amplification of LP01 and LP11 modes for the first time, that is, the differential modal gain (DMG) is dependent on the integral of the overlap factor difference over the EDF length. We also simulate the effect of pump mode beating on signal amplification: the modal gain varies periodically with the pump mode phase, and the beat length can affect the fluctuation period and amplitude of the DMG. The DMG can further be reduced by controlling the initial phases of the vector modes and properly designing the beat length of the FM-EDF. The similar process can expand to more signal modes, such as the simultaneous amplification of LP01x, LP11ex, LP11oy, LP21ex and LP21oy modes. The LP mode decomposition method is also applied to the beat effect between signal modes or the amplification of orbital angular momentum (OAM) modes. One can expect to implement an experiment on the FM-EDFA amplification with pump mode beating by optimally designing the FM-EDF structure, using a properly narrow linewidth pump laser and precisely controlling the pump mode coherence.

Quarter-wave Pancharatnam-Berry phase gradient liquid crystal-enabled dual-polarization optical edge detection.

Here, we present a novel, to the best of our knowledge, optical edge detection scheme that can be operated in both linear and circular polarization modes, leveraging an optical spatial differentiator constructed by quarter-wave Pancharatnam-Berry (P-B) phase gradient element. After explaining the theoretical mechanism, we utilize a quarter-wave P-B phase liquid crystal polarization grating to validate the dual-polarization optical edge detection capability. We demonstrate that the orientation of linear polarization and the spin of circular polarization dictate the transition between edge and bright-field images. Besides, the linear and circular polarization modes exhibit broadband and monochromatic responsive properties, respectively. This mechanism, dependent on wavelength and polarization, holds promise for applications in color image processing, chiral sensing imaging, and polarization-entangled quantum imaging.

Performing optical logic operations on linear polarization modes using diffractive deep neural networks

Performing optical logic operations on linear polarization modes using diffractive deep neural networks

Polarization reconfigurable transmitarray antenna utilizing single‐layer Huygen element for Ku‐band satellite communication

SummaryThis paper introduces a concept for designing a polarization reconfigurable transmitarray (PRT). The unit cell of the transmitarray utilizes Huygen elements, with dimensions measuring 0.6 ( corresponds to a frequency of 15 GHz). An equivalent circuit model is proposed for the unit cell based on the two‐port Z‐matrix. The proposed unit cells have a very low insertion loss of 0.5 dB at 15 GHz. The PRT is illuminated by a linearly polarized (LP) microstrip‐printed Yagi antenna. The transmitarray is designed using the proposed unit cells with a two‐level phase quantization. The collimated LP radiation emitted by the transmitarray subsequently traverses a polarization reconfigurable converter (PRC). The resultant radiation from the PRC can be either LP or circularly polarized (CP), contingent on the configuration of the PIN diodes employed within the PRC. The proposed PRT demonstrates a measured gain of 16 dBi when operating in the LP mode while achieving a peak gain of 15 dBic in the CP mode. The overall size of the proposed PRT is compact owing to a small f/d ratio (0.58). The practicality of the design is validated through fabrication and measurement. This innovative antenna design holds potential applications in the realm of Ku‐band uplink satellite communication.

All-Fiber Low-Modal-Crosstalk Demultiplexers for DSP-Free IM/DD LP-Mode MDM Transmission

Weakly coupled mode-division multiplexing (MDM) techniques supporting intensity modulation and direct detection (IM/DD) transmission are promising methods of enhancing the capacity of short-reach scenarios in which low-modal-crosstalk-mode demultiplexers for degenerate linear polarized (LP) modes are highly desired. In this paper, we review two degenerate-mode reception schemes. Firstly, a low-modal-crosstalk orthogonal combined reception method for degenerate modes is proposed based on all-fiber mode-selective couplers, in which signals in both degenerate modes are demultiplexed into the LP01 mode of single-mode fibers and then are multiplexed into the mutually orthogonal LP01 and LP11 modes of a two-mode fiber (TMF) for simultaneous detection. Secondly, a novel degenerate-mode-selective coupler consisting of an input few-mode fiber and an output TMF is proposed, which could demultiplex degenerate LP modes without any digital signal processing (DSP). Both demultiplexers are achieved based on the taper and polish process. The fabricated devices are characterized and compared. The results show that the proposed schemes can pave the way to the practical implementation of DSP-free IM/DD LP-mode MDM transmission systems.

Wideband Multi-polarization Reconfigurable Antenna based on Non-uniform Polarization Convert AMC Reflector

A novel design of wideband multi-polarization reconfigurable antenna is proposed, based on a non-uniform polarization convert artificial magnetic conductor (AMC) reflector. The proposed antenna consists of a radiator element and an AMC reflector. Firstly, a modified polarization convert AMC reflector is designed. The non-uniform AMC reflector causes an enhancement of 3 dB axial ratio (AR) performance. Secondly, a wideband linearly polarized monopole antenna is presented as the main radiator, utilizing the broadband characteristic of a C-shaped monopole. The polarization reconfigurability of the proposed antenna can be achieved by properly rotating the AMC reflector, which can be switched between linear polarization (LP), left-hand circular polarization (LHCP), and right-hand circular polarization (RHCP). A prototype of the proposed antenna is fabricated and experimented with to validate the theoretical performance. The measured results show a -10 dB impedance bandwidth of 42.7% and 44.4% for LP and CP modes, respectively, and a 3 dB AR bandwidth of 20% for CP modes. In addition, the measured peak gain reaches 8 dBi/dBic. A good agreement is shown between the simulation and measurement, pointing to the good performance of the proposed antenna.

Dual-color emissive OLED with orthogonal polarization modes

Linearly polarized organic light-emitting diodes have become appealing functional expansions of polarization optics and optoelectronic applications. However, the current linearly polarized diodes exhibit low polarization performance, cost-prohibitive process, and monochromatic modulation limit. Herein, we develop a switchable dual-color orthogonal linear polarization mode in organic light-emitting diode, based on a dielectric/metal nanograting-waveguide hybrid-microcavity using cost-efficient laser interference lithography and vacuum thermal evaporation. This acquired diode presents a transverse-electric/transverse-magnetic polarization extinction ratio of 15.8 dB with a divergence angle of ±30°, an external quantum efficiency of 2.25%, and orthogonal polarized colors from green to sky-blue. This rasterization of dielectric/metal-cathode further satisfies momentum matching between waveguide and air mode, diffracting both the targeted sky-blue transverse-electric mode and the off-confined green transverse-magnetic mode. Therefore, a polarization-encrypted colorful optical image is proposed, representing a significant step toward the low-cost high-performance linearly polarized light-emitting diodes and electrically-inspired polarization encryption for color images.

A Millimeter-Wave Broadband Multi-Mode Substrate-Integrated Gap Waveguide Traveling-Wave Antenna with Orbit Angular Momentum.

Orbit angular momentum (OAM) has been considered a new dimension for improving channel capacity in recent years. In this paper, a millimeter-wave broadband multi-mode waveguide traveling-wave antenna with OAM is proposed by innovatively utilizing the transmitted electromagnetic waves (EMWs) characteristic of substrate-integrated gap waveguides (SIGWs) to introduce phase delay, resulting in coupling to the radiate units with a phase jump. Nine "L"-shaped slot radiate elements are cut in a circular order at a certain angle on the SIGW to generate spin angular momentum (SAM) and OAM. To generate more OAM modes and match the antenna, four "Π"-shaped slot radiate units with a 90° relationship to each other are designed in this circular array. The simulation results show that the antenna operates at 28 GHz, with a -10 dB fractional bandwidth (FBW) = 35.7%, ranging from 25.50 to 35.85 GHz and a VSWR ≤ 1.5 dB from 28.60 to 32.0 GHz and 28.60 to 32.0 GHz. The antenna radiates a linear polarization (LP) mode with a gain of 9.3 dBi at 34.0~37.2 GHz, a l = 2 SAM-OAM (i.e., circular polarization OAM (CP-OAM)) mode with 8.04 dBi at 25.90~28.08 GHz, a l = 1 and l = 2 hybrid OAM mode with 5.7 dBi at 28.08~29.67 GHz, a SAM (i.e., left/right hand circular polarization (L/RHCP) mode with 4.6 dBi at 29.67~30.41 GHz, and a LP mode at 30.41~35.85 GHz. In addition, the waveguide transmits energy with a bandwidth ranging from 26.10 to 38.46 GHz. Within the in-band, only a quasi-TEM mode is transmitted with an energy transmission loss |S21| ≤ 2 dB.

Analysis of guided optical eigenmodes in magneto-optical fibers with applications to OAM mode selective couplers

Mode division multiplexing technology can regard each eigenmode in optical fibers as an independent channel to carry different data information, helpful for improving the transmission capacity of optical fiber communication systems. The spatial distribution, state of polarization and propagation constant of guided optical eigenmodes in the magneto-optical fiber are derived theoretically by the analysis of linear polarization and exact modes. The transverse distribution of the eigenmodes in the MO fiber can be constructed by those of exact modes in the conventional fiber. The effect of applied magnetic field on the eigenmodes and their effective refractive indices is studied. Simulation results show that, the eigenmodes in the MO fiber may be represented by the pseudo-modes of circular polarization () or the true modes of orbital angular momentum () when applied magnetic field is sufficiently large. The measurement method for weak magnetic field based on Stokes parameters is proposed. The magnetic tunability of OAM mode selective couplers is also analyzed.

Low crosstalk 125 μm cladding heterogeneous six-core few-mode fiber with air-hole array and trench structure

In order to be compatible with the current optical fiber communication network, we propose a 125 μm diameter heterogeneous six-core two linear polarization modes fiber with air-hole array and trench (HAT) structure. The coupled power theory and finite element method (FEM) are used to investigate inter-core crosstalk (ICXT), bending loss, and other properties. The HAT structure can effectively suppress ICXT; and the maximum ICXT is less than −38 dB/100 km in C + L band. The effective refractive index difference (Δneff) between modes is greater than 3 × 10-3, inter-mode crosstalk (IMXT) can be ignored. The maximum intrinsic loss is 0.187 dB/km; relative core multiplicity factor reaches 32.21. The relative spatial efficiency is 18 times that of traditional single-mode fibers. This fiber can be produced by chemical vapor deposition and existing optical fiber manufacturing technology. The designed fiber can be directly connected to the communication network to reduce the cost of equipment renewal, and the communication capacity can be increased by 18 times.

Broadband design of silica-PLC mode-dependent-loss equalizer for 2LP-mode transmission systems.

A new configuration of mode-dependent-loss (MDL) equalizer for two linearly-polarized mode transmission systems using the silica planar lightwave circuit platform is proposed. This device acts as an LP01-mode attenuator (precisely, LP01/LP21 mode converter) to adjust the MDL keeping a high transmission of the LP11 modes. Almost all components constructing the device are based on the adiabatic mode conversion, which brings broadband operation. Especially, a newly proposed E12/E22 mode converter plays a key role in broadband MDL equalization. It is numerically revealed that the flattened spectra with designated transmission can be obtained for the wavelength from 1200 nm to 1650 nm.

Performance of the merged APPLE-Knot undulator for soft x-ray beamline in medium energy ring

APPLE-Knot undulator can effectively solve the on-axis heat load problem and is proven to perform well in VUV beamline and soft x-ray beamline in high energy storage ring. However, for soft x-ray beamline in a medium energy ring, whether the APPLE-Knot undulator excels the APPLE undulator is still a question. Here, a merged APPLE-Knot undulator is studied to generate soft x-ray in a medium energy ring. Its advantages and problems are discussed. Though the on-axis heat load of the APPLE-Knot undulator is lower in linear polarization modes compared to the APPLE undulator, its flux is lower. The APPLE-Knot undulator shows no advantage when only fundamental harmonic is needed. However, in circular polarization mode, the APPLE-Knot undulator shows the ability to cover a broader energy range which can remedy the notable shortcoming of the APPLE undulator.

Chip-to-chip optical multimode communication with universal mode processors

The increasing amount of data exchange requires higher-capacity optical communication links. Mode division multiplexing (MDM) is considered as a promising technology to support the higher data throughput. In an MDM system, the mode generator and sorter are the backbone. However, most of the current schemes lack the programmability and universality, which makes the MDM link susceptible to the mode crosstalk and environmental disturbances. In this paper, we propose an intelligent multimode optical communication link using universal mode processing (generation and sorting) chips. The mode processor consists of a programmable 4 × 4 Mach Zehnder interferometer (MZI) network and can be intelligently configured to generate or sort both quasi linearly polarized (LP) modes and orbital angular momentum (OAM) modes in any desired routing state. We experimentally establish a chip-to-chip MDM communication system. The mode basis can be freely switched between four LP modes and four OAM modes. We also demonstrate the multimode optical communication capability at a data rate of 25 Gbit/s. The proposed scheme shows significant advantages in terms of universality, intelligence, programmability and resistance to mode crosstalk, environmental disturbances, and fabrication errors, demonstrating that the MZI-based reconfigurable mode processor chip has great potential in long-distance chip-to-chip multimode optical communication systems.

Ultra‐High Bandwidth Density and Power Efficiency Chip‐To‐Chip Multimode Transmission through a Rectangular Core Few‐Mode Fiber

AbstractOptical interconnects have emerged as promising solutions for assisting electrical interconnects in short‐reach scenarios, where high bandwidth density and energy efficiency are of particular importance. Mode‐division multiplexing (MDM), capable of enhancing the bandwidth density and energy efficiency of optical systems, has drawn tremendous interest. However, the chip‐to‐chip MDM optical interconnects are impeded by the multimode chip‐fiber interfaces, where the transverse modes on the MDM chip mismatch with the linear polarization modes in the circular core few‐mode fiber (CCF). Moreover, the high differential group delays (DGDs) of a conventional CCF make the digital signal processing (DSP) computation complex thus consuming high power. To overcome these bottlenecks, a new multimode coupling solution based on a rectangular core few‐mode fiber with ultra‐low DGDs and an integrated multimode coupler is proposed. Based on this coupling scheme, a chip‐to‐chip MDM transmission experiment is performed on the TE00, TM00, TE10, and TM10 modes, and the highest bandwidth density of 19.4 Tb s mm −1 is realized at the chip facet. The DSP power consumption is ≈6% of a conventional CCF‐based system. It is believed that this work will pave the way for ultra‐compact, high density, low cost, and low computation‐complexity optical interconnects, such as data centers, cloud computing, and telecommunications.

Low-CD weakly-coupled FMF for short-reach IM/DD MDM transmission.

Weakly-coupled mode division multiplexing (MDM) technique is a promising candidate for capacity enhancement of short-reach optical interconnections, for which the multiple-ring-core few-mode fiber (MRC-FMF) has been proven to be an effective design method to suppress distributed modal crosstalk. Similar to low chromatic-dispersion (CD) O-band transmission based on single-mode fibers (SMF), all the mode channels in a weakly-coupled FMF for short-reach applications should achieve low CD to support intensity-modulation/direct-detection (IM/DD) transmission. In this paper, we propose, for the first time to the best of our knowledge, an index perturbation method to adjust both effective index and CD of each mode in an MRC-FMF. Firstly, an accurate modeling method to model the relationship between SiO2-GeO2 material index and the germanium concentration at different wavelengths is proposed by analyzing the index characteristics of 4 kinds of germanium-doped fused silica SMFs at the same fabrication processing, which could be utilized to calculate the CD characteristics for an MRC-FMF with perturbed index profile. Then, based on the perturbation method considering the influences on both effective index and CD, a weakly-coupled low-CD MRC-FMF supporting 4 linearly-polarized (LP) modes is designed and fabricated. The measured minimum effective index difference min|Δneff| among all modes is larger than 1.3 × 10-3, and the CD values of all the modes lie between -6 and +6 ps/km/nm ranging from 1280 to 1320 nm, which agree well with the design. The 2-km transmission experiment indicates that the fabricated MRC-FMF could support stable digital-signal-processing (DSP)-free IM/DD transmission for all the 4 LP modes. This work is beneficial to the application of short-reach weakly-coupled MDM systems.

Two fiber-bundle-type FI/FO devices of low insertion loss and cross talk applied for connecting 13-core 5-mode fiber.

Two fiber-bundle-typed fan-in/fan-out (FI/FO) devices, "wavy hexagon-shaped silhouette" type (W-FI/FO) and "tortoise-shaped silhouette" type (T-FI/FO), have been proposed and manufactured based on tapering glass tubes for docking with a self-made 13-core 5-mode fiber. The W-FI/FO device consists of 19 5-mode fibers and has an extended layout based on the 13-core 5-mode fiber structure. It could dock multiple fibers with 19 or 13 cores of the same size standards. When connecting it with 13-core 5-mode, the average losses (ILs) of its five modes are 1.07 dB, 2.95 dB, 3.42 dB, 3.65 dB, and 4.38 dB. The cross talks of the five linearly polarized (LP) modes are -69.1 dB, -64.7 dB, -44.2 dB, -43.9 dB, and -39.1 dB. The T-FI/FO device has a similar core arrangement to the 13-core 5-mode fiber and its average ILs of the five LP modes are 0.23 dB, 1.31 dB, 2.09 dB, 2.66 dB, and 3.03 dB. The cross talks of its five LP modes between adjacent cores are -72.8 dB, -67.8 dB, -43.6 dB, -40.0 dB, and -35.3 dB. The IL and cross talk of the LP01 mode are of satisfactory values, which are 0.23 dB and -72.8 dB, respectively. These two proposed FI/FO devices are expected to be used for high-speed optical interconnection and fiber communication.

Wideband and low profile multipolarization reconfigurable antenna based on metasurface

AbstractIn this letter, a wideband and low‐profile multipolarization reconfigurable antenna based on metasurface (MTS) is proposed. The antenna mainly contains two parts, an upper layer of MTS and a bottom layer of circular slot antenna. The MTS acts as a polarization controller, by mechanically rotating the MTS layer at a proper angle while keeping the circular slot antenna remain stationary, the polarization mode of the antenna can be switched to linear polarization (LP), left‐hand circular polarization (LHCP), and right‐hand circular polarization (RHCP). The experimented −10 dB impedance bandwidth of 37.8% and 54% for LP and circular polarization (CP) modes, respectively. The measured overlapped 3‐dB AR bandwidth is 22.2% for both CP modes, covering from 3.2 to 4 GHz. Moreover, the measured peak gain of the presented antenna reaches 9 dBi and 8 dBic for LP and CP modes, with a lower profile of 0.05 λ0.