High Circular Polarization Research Articles

Multimode light generation in an injection semiconductor laser based on a chiral AlAs/(Al, Ga)As/GaAs microcavity

Experimental investigations of chiral injection AlAs/(Al, Ga)As/GaAs vertical-cavity surface-emitting lasers in the multimode generation regime are performed. A high circular polarization degree 70% of different generation modes measured with a high spectral resolution, is demonstrated. Detailed maps of spatial and angular distribution of laser radiation intensity were constructed.

A High Gain Circularly Polarized Slot Antenna Array for 5G Millimeter-Wave Applications

An air-filled substrate-integrated waveguide (AF-SIW) circularly polarized (CP) 1 × 8 mm wave antenna array is presented for fifth-generation (5G) applications. The presented slot antenna array consists of three layers of PCB and one layer of aluminum, which serve as the AF-SIW feeding network and the metal cavity radiation element, respectively. The CP characteristic is achieved by the use of an S-shaped aluminum radiation cavity on the top of the AF-SIW feeding network. The air-filled substrate-integrated waveguide technique is unitized to achieve high radiation efficiency. A wide input impedance bandwidth of 18.4% is obtained for the proposed antenna scheme, ranging from 34.5 GHz to 41.5 GHz, with a peak gain of 18 dBic. As for CP characteristic, the proposed antenna possesses a wide 3 dB axial ratio (AR) bandwidth, which is 16.4% (36.5 GHz to 43 GHz). The antenna scheme is fabricated and measured to verify the potential application as well as the promising performance. The measured results of the 1 × 8 antenna array shows that the wide AR as well as the input impedance are simultaneously achieved, which coincide well with the simulated results. Also, the measured results indicate that the proposed antenna scheme might be a good candidate for future mobile applications.

High efficiency and circular polarization in SATCOM phased arrays using tri-ridge apertures

A new antenna array architecture is proposed here to overcome a current bottleneck in phased arrays concerning the enhancement of radiation efficiency and avoidance of scan blindness. In contrast to the conventional approach of using patches with circular or square geometries that exploit 90∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^\\circ$$\\end{document} or 180∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^\\circ$$\\end{document} rotational symmetry, this work proposes to use waveguide radiating elements based on 120∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^\\circ$$\\end{document} symmetry. To implement such symmetry, the tri-ridge aperture is proposed, and its capability to scan widely within a broad frequency bandwidth is demonstrated. A modal analysis is performed to explain the physical phenomena underlying such superior performance. A successful experimental validation is provided by means of a monolithic prototype built in metal additive manufacturing. The measured results show, for the first time, that it is possible to achieve high radiation efficiency and circular polarization when scanning widely in a broad bandwidth. Such an accomplishment constitutes a major achievement in the field of active electronically steered phased arrays, and impacts significantly the capabilities and potential of modern radar and communication systems.

Polarimetric characterization of Chandrayaan-3 landing site near lunar south pole using high resolution Chandrayaan-2 DFSAR data

The Chandrayaan-3 (CH3) Vikram lander presents an unique opportunity to study the radar scattering behavior of the landing site as well as human-made dihedral structure on the lunar surface. This opportunity is made possible by the Dual-Frequency Synthetic Aperture Radar (DFSAR) sensor onboard the Chandrayaan-2 orbiter, which has the highest resolution and polarimetric capabilities compared to any planetary SAR sensor. To explore this, we utilized DFSAR to capture high-resolution images of the CH3 landing site during pre-landing and post-landing condition, with a pixel spacing as fine as 1 m, in a hybrid-pol mode. The landing site exhibits dominant volume and even-bounce radar scattering behavior similar to an ideal dihedral geometry. Furthermore, we observed an exceptionally high Circular Polarization Ratio value at the landing site (1.99 ± 0.30), a rarity among natural features on the lunar surface. Besides, the landing site is characterized by enhanced average dielectric constant value (5.76 ± 3.11). The post-landing DFSAR image reveals a 177 m2 area, surrounding the CH3 landing location, characterized by high CPR and elevated even bounce and volume scattering. The drastic enhancement of the average CPR value (7-times), dielectric value (2-times), even bounce and volume scattering in the landing site, in comparison with the pre-landing DFSAR observation, is due to presence of lander module and disturbance in the regolith structure in the landing area. The polarimetric characteristics of the landing site distinguish it from the major natural features on the lunar surface, such as regolith, debris flow, and impact ejecta. This investigation is of utmost importance as it emphasizes the effectiveness of high-resolution DFSAR acquisitions for evaluating the polarimetric behavior of small-scale features, which can be invaluable for characterizing landing sites in upcoming missions.

A Volume-limited Radio Search for Magnetic Activity in 140 Exoplanets with the Very Large Array

We present results from a search for radio emission in 77 stellar systems hosting 140 exoplanets, predominantly within 17.5 pc using the Very Large Array (VLA) at 4–8 GHz. This is the largest and most sensitive search to date for radio emission in exoplanetary systems in the GHz frequency range. We obtained new observations of 58 systems and analyzed archival observations of an additional 19 systems. Our choice of frequency and volume limit is motivated by radio detections of ultracool dwarfs (UCDs), including T dwarfs with masses at the exoplanet threshold of ∼13 M J. Our surveyed exoplanets span a mass range of ≈10−3–10 M J and semimajor axes of ≈10−2–10 au. We detect a single target—GJ 3323 (M4) hosting two exoplanets with minimum masses of 2 and 2.3 M ⊕—with a circular polarization fraction of ≈40%; the radio luminosity agrees with its known X-ray luminosity and the Güdel–Benz relation for stellar activity suggesting a likely stellar origin, but the high circular polarization fraction may also be indicative of star–planet interaction. For the remaining sources our 3σ upper limits are generally L ν ≲ 1012.5 erg s−1 Hz−1, comparable to the lowest radio luminosities in UCDs. Our results are consistent with previous targeted searches of individual systems at GHz frequencies while greatly expanding the sample size. Our sensitivity is comparable to predicted fluxes for some systems considered candidates for detectable star–planet interaction. Observations with future instruments such as the Square Kilometre Array and Next-Generation VLA will be necessary to further constrain emission mechanisms from exoplanet systems at GHz frequencies.

Highly-Polarized Emission Provided by Giant Optical Orientation of Exciton Spins in Lead Halide Perovskite Crystals.

Quantum technologic and spintronic applications require reliable material platforms that enable significant and long-living spin polarization of excitations, the ability to manipulate it optically in external fields, and the possibility to implement quantum correlations between spins, i.e., entanglement. Here it is demonstrated that these conditions are met in bulk crystals of lead halide perovskites. A giant optical orientation of 85% of excitons, approaching the ultimate limit of unity, in FA0.9Cs0.1PbI2.8Br0.2 crystals is reported. The exciton spin orientation is maintained during the exciton lifetime of 55ps resulting in high circular polarization of the exciton emission. The optical orientation is robust to detuning of the excitation energy up to 0.3eV above the exciton resonance and remains larger than 20% up to detunings of 0.9eV. It evidences pure chiral selection rules and suppressed spin relaxation of electrons and holes, even with large kinetic energies. The exciton and electron-hole recombinations are distinguished by means of the spin dynamics detected via coherent spin quantum beats in magnetic field. Further, electron-hole spin correlations are demonstrated through linear polarization beats after circularly polarized excitation. These findings are supported by atomistic calculations. All-in-all, the results establish lead halide perovskite semiconductors as suitable platform for quantumtechnologies.

Scalable Nanoimprint Manufacturing of Functional Multilayer Metasurface Devices

AbstractOptical metasurfaces, consisting of subwavelength‐scale meta‐atom arrays, hold great promise of overcoming the fundamental limitations of conventional optics. Due to their structural complexity, metasurfaces usually require high‐resolution yet slow and expensive fabrication processes. Here, using a metasurface polarimetric imaging device as an example, the photonic structures and the Nanoimprint lithography (NIL) processes are designed, creating two separate NIL molds over a patterning area of > 20 mm2 with designed Moiré alignment markers by electron‐beam writing, and further subsequently integrate silicon and aluminum metasurface structures on a chip. Uniquely, the silicon and aluminum metasurfaces are fabricated by using the nanolithography and 3D pattern‐transfer capabilities of NIL, respectively, achieving nanometer‐scale linewidth uniformity, sub‐200 nm translational overlay accuracy, and <0.017 rotational alignment error while significantly reducing fabrication complexity and surface roughness. The micro‐sized multilayer metasurfaces have high circular polarization extinction ratios as large as ≈20 and ≈80 in blue and red wavelengths. Further, the metasurface chip‐integrated CMOS imager demonstrates high accuracy in broad‐band, full Stokes parameter analysis in the visible wavelength ranges and single‐shot polarimetric imaging. This novel, NIL‐based, multilayered nanomanufacturing approach is applicable to the scalable production of large‐area functional structures for ultra‐compact optic, electronic, and quantum devices.

An Ultra High Frequency Radio Frequency Identification Compatible Circular Polarized Microstrip Antenna Array

This study focuses on the development, simulation, and practical validation of a metal-only microstrip patch antenna and its array designed to increase gain. The antenna is specifically designed to meet the growing demand for reliable and efficient RFID systems in various fields, such as asset tracking, inventory management, and smart logistics. Our design utilizes a truncated patch with an air substrate to achieve high gain and circular polarization. The antenna's dimensions measure 468 × 188 × 31 mm³ and deliver impressive performance metrics, boasting a return loss |S11| of -18.21 dB and an estimated gain exceeding 10.6 dBi. These figures compare favorably with the simulated results, which indicate an |S11| of -20.8 dB and a total gain of 11.2 dBi. Our microstrip antenna array demonstrated consistent Circular Polarization quality throughout the radiation angle, with an Axial Ratio of less than 3 dB. This antenna has emerged as a compelling solution for UHF-band RFID technology to meet the demands of various real-world applications.

Layer‐By‐Layer Chiral Induction of Fluorene‐Based Metal–Organic Framework Films for Circularly Polarized Luminescence Sensing of Enantiomers

AbstractDeveloping films of chiral metal–organic frameworks (MOFs) with high circular polarization luminescence (CPL) is facing a great challenge for chiral sensing applications. Herein, a layer‐by‐layer chiral induction method is first reported to prepare enantiopure MOF films for CPL sensing. By layer‐by‐layer induction with the chiral inductor camphorsulfonic acid, fluorene‐based chiral MOF D/L‐ZnHF‐SO2 film (HF‐SO2 = 3,7‐Dibenzothiophenedicarboxylate, 5,5‐dioxide) with preferential growth orientation and homogeneous surface are prepared, which shows strong chiral feature and CPL with higher asymmetry factor of ±0.073. In addition, by mixed ligand approach, the isostructural fluorene ligand 9‐fluororenone‐2,7‐dicarboxylate is chosen to replace part of HF‐SO2 for preparing a series of chiral MOF films with tunable CPL emission. Furthermore, the prepared chiral MOF films with strong CPL performance are further utilized for enantiomers sensing. The CPL changes consisted with enantioselective adsorption results showed that D/L‐ZnHF‐SO2 film has good discrimination against chiral R/S‐phenylethylamine enantiomers, first reporting chiral MOF‐based candidates for the application in CPL sensing of enantiomers. This work provides a facile and effective approach for preparing chiral MOF films materials with high and tunable CPL performance, and also gives a new way to achieve CPL sensing of chiral enantiomers.

Development of Compact Wideband and High Gain Circularly Polarized Antenna for C-Band Applications

Development of Compact Wideband and High Gain Circularly Polarized Antenna for C-Band Applications

Deep Synoptic Array Science: Polarimetry of 25 New Fast Radio Bursts Provides Insights into Their Origins

We report on a full-polarization analysis of the first 25 as yet nonrepeating fast radio bursts (FRBs) detected at 1.4 GHz by the 110-antenna Deep Synoptic Array (DSA-110) during commissioning observations. We present details of the data-reduction, calibration, and analysis procedures developed for this novel instrument. Faraday rotation measures (RMs) are searched between ±106 rad m−2 and detected for 20 FRBs, with magnitudes ranging from 4 to 4670 rad m−2. Fifteen out of 25 FRBs are consistent with 100% polarization, 10 of which have high (≥70%) linear-polarization fractions and two of which have high (≥30%) circular-polarization fractions. Our results disfavor multipath RM scattering as a dominant depolarization mechanism. Polarization-state and possible RM variations are observed in the four FRBs with multiple subcomponents. We combine the DSA-110 sample with polarimetry of previously published FRBs, and compare the polarization properties of FRB subpopulations and FRBs with Galactic pulsars. Although FRB polarization fractions are typically higher than those of Galactic pulsars, and cover a wider range than those of pulsar single pulses, they resemble those of the youngest (characteristic ages <105 yr) pulsars. Our results support a scenario wherein FRB emission is intrinsically highly linearly polarized, and propagation effects can result in conversion to circular polarization and depolarization. Young pulsar emission and magnetospheric propagation geometries may form a useful analogy for the origin of FRB polarization.

Multi-Mode Long-Wavelength GaAs/AlGaAs Quantum Well Infrared Photodetectors for Circular Polarization Detection

We present an integrated device combining a double L-shaped chiral metasurface with long-wavelength GaAs/AlGaAs quantum well infrared photodetectors (QWIPs), achieving a circular polarized extinction ratio (CPER) as high as 45 in the long-wavelength infrared range of 7–9 μm. The unit of the chiral metasurface array consists of two structurally identical L-shaped gold structures with central symmetry. The CPER of the double L-shaped QWIPs is 14 times higher than that of a single L-shaped QWIP. The device operates in three modes within the detection band: the microcavity mode, the surface plasmon polariton (SPP) mode, and the hybrid mode. The double L-shaped chiral structure selects and reflects a small portion of left-handed circularly polarized light (LCP), while the majority enters the device and excites SPP modes with the bottom gold grating layer, leading to an absorption enhancement. In contrast, right-handed circularly polarized light (RCP) is mostly reflected with limited excitation of SPP waves. QWIPs exhibit a peak absorption of 0.8 and a coupling efficiency of 2700% in the active region of the quantum well due to the combined effects of the microcavity and SPP modes, in which the SPP mode plays a dominant role. The proposed device maintains high circular polarization discrimination capability under large incident angles and can be applied in spectral imaging.

Enhancement of circularly polarized electroluminescence via reflection reversal under a magnetic field

Red-MCPEL could be emitted from an MCP-OLED containing achiral PtOEP under a 1.7-T EMF. The degree of light rotation and luminance of this CP-OLED can be amplified through the synergistic effects of light reflection reversal and an EMF.

Compact High Gain Wideband Circularly Polarized Non-Uniform Metasurface Antenna Through Improved Mode Coupling

Compact High Gain Wideband Circularly Polarized Non-Uniform Metasurface Antenna Through Improved Mode Coupling

A Compact Wideband Printed 4 × 4 MIMO Antenna with High Gain and Circular Polarization Characteristics for mm-wave 5G NR n260 Applications

A Compact Wideband Printed 4 × 4 MIMO Antenna with High Gain and Circular Polarization Characteristics for mm-wave 5G NR n260 Applications

Compact on-chip THz circular polarization detectors with high discrimination based on chiral plasmonic antennas

THz circular polarization detection is an important technology in many applications of THz waves. With the ongoing miniaturization of optoelectronic systems, there is an increasing demand for compact on-chip THz circular polarization detectors. Here, we propose what we belive to be a novel device of this kind based on the composite structure of quantum well (QW) infrared detection material sandwiched by a chiral plasmonic antenna array and a metal plane. Due to the circular polarization dependent light coupling discrimination provided by the cavity enhanced chiral antenna and the second polarization selection of the QWs, a circular polarization extinction ratio as high as 25 is achieved, surpassing all reported on-chip THz circular polarization detectors. Due to the field enhancement at the QWs, the absorption for the principle circular polarization is 15 times higher than a standard reference. The absorption peak can be tuned over the range from 6.41 to 6.56 THz, while considerable absorption enhancement and high circular polarization discrimination are preserved even under non-normal incidence. Our proposed device's structure is compatible with the QWIP focal plane array and has far-reaching application prospects opens a new avenue to the development of high-performance compact on-chip THz circular polarization detectors.

High Comprehensive Circularly Polarized Electroluminescence Performance Improved by Chiral Coassembled Host Materials

AbstractCircularly polarized organic light‐emitting diodes are of great significance in 3D displays. However, achieving circularly polarized electroluminescence (CP‐EL) simultaneously with a large dissymmetry factor (gEL) and high efficiency still remains a formidable challenge. Herein, a facile and efficient strategy is developed for improving the performance of CP‐EL devices using device emitting layers of chiral coassembled helix nanofiber host materials. Chiral coassembled helix nanofiber host materials ((S‐/R‐2Cz)0.2‐(PFpy)0.8) could be smartly constructed through intermolecular π–π stacking interactions between the achiral conjugated pyridine‐based polymer acceptor (PFpy) and the chiral binaphthyl‐based donor (S‐/R‐2Cz). Significantly, the resulting chiral coassembled hosts (S‐/R‐2Cz)0.2‐(PFpy)0.8 greatly promote a commercially available achiral phosphorescence emitter to achieve solution‐processed red CP‐EL device performances at 620 nm with a high external quantum efficiency of 4.1% and a large |gEL| value of 0.014.

Near zero index Metamaterial-based SIW antenna for 6G Sub-Terahertz applications

This paper introduces a novel high-gain circularly polarized (CP) antenna that utilizes a NRZI (Near Zero Refractive Index) and MNG (Mu Negative) metamaterialslab. The antenna employs a substrate integrated waveguide (SIW) technique and loaded with compact square split ring resonator (SSRR) combined with a hexagonal-shaped structure by a 0.2 mm width slab as a unit cell to achieve high gain and circular polarization. The metamaterial characteristics were examined through material wave propagation in two main directions at the y and x-axis. For wave propagation at the y-axis, the MTM structure demonstrates mu-near-zero (MNZ) with more than 88 GHz bandwidth, NZRI, and Epsilon-Near-Zero (ENZ) properties. However, for x-axis wave propagation, it indicates a wide negative range of single mu metamaterial from 176 to 220 GHz, NZRI, and ENZ properties. By using six unit cells, the antenna acts as an aperture-efficient focusing metasurface lens and polarization converter for a primary source antenna. The NRZI-MNG enhances the gain of the suggested antenna by 6–7 dB, and converts the linearly polarized wave emitted by the patch antenna into circularly polarized waves. The designed antenna has an impedance bandwidth from 176.5 to 285 GHz, with a 3 dB axial ratio achieved from 177 to 204 GHz. The peak gain of the antenna is 11.3 dBi at 223 GHz, and a gain of around 10 dBi is achieved over the entire CP bandwidth with a good cross-polarization level. In addition, the transmittance of the suggested metamaterial antenna is between 80% and 90% in the operating band. These excellent performances make this antenna very promising for sub-THz 6G applications.

Generation of high circular polarization of interstellar Lyman α radiation triggering biological homochirality

ABSTRACT The homochirality of biological molecules on Earth is a long-standing mystery regarding the origin of life. Circularly polarized ultraviolet (UV) light could induce the enantiomeric excess of biological molecules in the interstellar medium, leading to the homochirality on Earth. By performing 3D radiation transfer simulations with multiple scattering processes in interstellar dusty slabs, we study the generation of the circular polarization (CP) of UV light at Lyα ($\lambda = 0.1216~{\rm \mu m}$) as well as at near-infrared (NIR, $\lambda = 2.14~{\rm \mu m}$) wavelengths. Our simulations show that the distributions of CP exhibit a symmetric quadrupole pattern, regardless of wavelength and viewing angle. The CP degree of scattered light from a dusty slab composed of aligned grains is ∼15 per cent for Lyα and ∼3 per cent at NIR wavelengths in the case of oblate grains with an Mathis-Rumpl-Nordsieck size distribution. We find that the CP degree of Lyα is well correlated with that in the NIR regardless of viewing angle, whilst being a factor of ∼5 higher. Thus, a high CP of Lyα is expected at sites where NIR CP is detected. We suggest that such circularly polarized Lyα may initiate the enantiomeric excess of biological molecules in space.

Wideband Circularly Polarized mm-Wave Array Antenna Using H-Shaped Low-Axial-Ratio Apertures

An H-shaped all-metal radiating element comprising an active and a coupled slot has been proposed to design wideband high-efficiency circularly-polarized antenna arrays. The proper excitation of several modes on the coupled slot enables a wide axial ratio bandwidth with high circular polarization purity. In order to feed an array of such radiating elements, a simple and scalable two-layer corporate network, implemented in groove gap waveguide technology, is conceived. Those good frequency properties have been confirmed by the fabrication of a prototype, whose experimental results report a 1-dB axial ratio bandwidth of 22%. In addition, a peak radiation efficiency of 97% with good pattern stability, and an impedance bandwidth of 21% with high return loss, have been measured. The high circular polarization purity demonstrated by these wideband apertures makes them particularly suitable for Ka-band satellite communications antennas.