Circularly Polarized Research Articles

Optical Möbius strips in isotropic random non-paraxial light

Abstract The statistics of Möbius strips with various topologies, formed by the axes of polarization ellipses as they are traced along a closed circular contour of small size passing through the center of a solitary circular polarization singularity line (C-line), have been investigated both analytically and numerically in a random isotropic electromagnetic field. Found are the analytical expressions for the joint probability density function of the differential characteristics of the random isotropic electromagnetic field, which allow for the determination of the topological properties of diagrams of polarization ellipses and the normal vectors to them, as well as the optical strips that arise in the space around C-lines.

Customizable Generation of Arbitrary‐Order Polarization Vortices by Spin‐Decoupled Geometric Phases

AbstractDue to nontrivial field topologies, polarization vortices carrying polarization singularities have attracted increasing interest in the fields of optics and photonics. However, the conventional methods for generation of polarization vortcies still suffer from the complexity and the heavy bulk. In this work, taking advantage of spin‐decoupled geometric phase in metasurfaces, a novel method is proposed to generate polarization vortices with customizable topological charges. By tailoring spin‐decoupled geometric phases generated by the metasurface, distinct helical phase profiles can be imparted to left‐ and right‐handed circularly polarized components. Consequently, two scalar vortices with different topological charges can be simultaneously generated in the two orthogonal circular polarization components, leading to the generation of the polarization vortices with the needed topological charges and the diverse morphologies. Both simulation and experimental results well demonstrate the method. Owing to the nondispersive feature of geometric phases, the designed metasurface works well in a wide frequency band. The proposed method contributes a reliable and feasible solution for customizing the generation of polarization vortices, which can be further transposed to other frequencies and applied to information encoding and polarization detection etc.

Large-scale fabrication of meta-axicon with circular polarization on CMOS platform

Abstract Metasurfaces, consisting of arrays of subwavelength structures, are lightweight and compact while being capable of implementing the functions of traditional bulky optical components. Furthermore, they have the potential to significantly improve complex optical systems in terms of space and cost, as they can simultaneously implement multiple functions. The wafer-scale mass production method based on the CMOS (complementary metal oxide semiconductor) process plays a crucial role in the modern semiconductor industry. This approach can also be applied to the production of metasurfaces, thereby accelerating the entry of metasurfaces into industrial applications. In this study, we demonstrated the mass production of large-area meta-axicons with a diameter of 2 mm on an 8-inch wafer using DUV (Deep Ultraviolet) photolithography. The proposed meta-axicon designed here is based on PB (Pancharatnam–Berry) phase and is engineered to simultaneously modulate the phase and polarization of light. In practice, the fabricated meta-axicon generated a circularly polarized Bessel beam with a depth of focus (DoF) of approximately 2.3 mm in the vicinity of 980 nm. We anticipate that the mass production of large-area meta-axicons on this CMOS platform can offer various advantages in optical communication, laser drilling, optical trapping, and tweezing applications.

Reversible Local Protonation-Deprotonation: Tuning Stimuli-Responsive Circularly Polarized Luminescence in Chiral Hybrid Zinc Halides for Anti-Counterfeiting and Encryption.

Precise control over the organic composition is crucial for tailoring the distinctive structures and properties of hybrid metal halides. However, this approach is seldom utilized to develop materials that exhibit stimuli-responsive circularly polarized luminescence (CPL). Herein, we present the synthesis and characterization of enantiomeric hybrid zinc bromides: biprotonated ((R/S)-C12H16N2)ZnBr4 ((R/S-LH2)ZnBr4) and monoprotonated ((R/S)-C12H15N2)2ZnBr4 ((R/S-LH1)2ZnBr4), derived from the chiral organic amine (R/S)-2,3,4,9-Tetrahydro-1H-carbazol-3-amine ((R/S)-C12H14N2). These compounds showcase luminescent properties; the zero-dimensional biprotonated form emits green light at 505 nm, while the monoprotonated form, with a pseudo-layered structure, displays red luminescence at 599 and 649 nm. Remarkably, the reversible local protonation-deprotonation behavior of the organic cations allows for exposure to polar solvents and heating to induce reversible structural and luminescent transformations between the two forms. Theoretical calculations reveal that the lower energy barrier associated with the deprotonation process within the pyrrole ring is responsible for the local protonation-deprotonation behavior observed. These enantiomorphic hybrid zinc bromides also exhibit switchable circular dichroism (CD) and CPL properties. Furthermore, their chloride counterparts were successfully obtained by adjusting the halogen ions. Importantly, the unique stimuli-responsive CPL characteristics position these hybrid zinc halides as promising candidates for applications in information storage, anti-counterfeiting, and information encryption.

Reversible Local Protonation‐Deprotonation: Tuning Stimuli‐Responsive Circularly Polarized Luminescence in Chiral Hybrid Zinc Halides for Anti‐Counterfeiting and Encryption

AbstractPrecise control over the organic composition is crucial for tailoring the distinctive structures and properties of hybrid metal halides. However, this approach is seldom utilized to develop materials that exhibit stimuli‐responsive circularly polarized luminescence (CPL). Herein, we present the synthesis and characterization of enantiomeric hybrid zinc bromides: biprotonated ((R/S)‐C12H16N2)ZnBr4 ((R/S‐LH2)ZnBr4) and monoprotonated ((R/S)‐C12H15N2)2ZnBr4 ((R/S‐LH1)2ZnBr4), derived from the chiral organic amine (R/S)‐2,3,4,9‐Tetrahydro‐1H‐carbazol‐3‐amine ((R/S)‐C12H14N2). These compounds showcase luminescent properties; the zero‐dimensional biprotonated form emits green light at 505 nm, while the monoprotonated form, with a pseudo‐layered structure, displays red luminescence at 599 and 649 nm. Remarkably, the reversible local protonation‐deprotonation behavior of the organic cations allows for exposure to polar solvents and heating to induce reversible structural and luminescent transformations between the two forms. Theoretical calculations reveal that the lower energy barrier associated with the deprotonation process within the pyrrole ring is responsible for the local protonation‐deprotonation behavior observed. These enantiomorphic hybrid zinc bromides also exhibit switchable circular dichroism (CD) and CPL properties. Furthermore, their chloride counterparts were successfully obtained by adjusting the halogen ions. Importantly, the unique stimuli‐responsive CPL characteristics position these hybrid zinc halides as promising candidates for applications in information storage, anti‐counterfeiting, and information encryption.

Helical Star-Shaped Bottlebrush Polymers: From Controlled Synthesis to Tunable Photoluminescence and Circularly Polarized Luminescence.

The controlled synthesis of star-shaped bottlebrush polymers with tunable topologies is a challenge. However, such materials may exhibit distinct photoluminescence properties. Bottlebrush polymers have polymerization-induced emission (PIE) properties due to their aggregated side chains, and aggregation-induced emission (AIE) is also a unique luminescent property. In this work, we prepared a variety of highly active alkyne Pd catalysts and polymerized poly(L/D-lactic acid) macromonomers containing polymerizable phenylisocyanide groups as end groups to obtain a variety of topologically structured bottlebrush polymers with controllable molecular weights and narrow molecular weight distributions. Bottlebrush polymers with tetraphenyl ethylene (TPE) units as the core exhibit tunable photoluminescence and circularly polarized luminescence properties. We propose that such properties are due to the unique AIE characteristics of the TPE unit combined with the PIE characteristics of the bottlebrush polymer.

AcpAS: An Advanced Circularly Polarized Antenna Structure for an Airborne Relay Communication System

The airborne relay system is an important support for improving the stability of communication systems in complex electromagnetic environments. As a key component of the airborne relay system, the antenna needs to have characteristics such as high gain, dual circular polarization, wide beam coverage, and miniaturization. Based on the septum circular polarizer, this paper proposes a high-performance circularly polarized antenna structure suitable for airborne relay systems, named AcpAS. The structure consists of a coaxial feed port, a coaxial-to-waveguide transition, a septum circular polarizer, and a parabolic metal housing. Based on this structure, two antennas operating at 19.6 GHz to 21.6 GHz and 29.2 GHz to 31.2 GHz are designed in this paper. Simulated and measured results show that the two antennas have dual circular polarization characteristics, with beam coverage range of more than ±55° for gains higher than 0 dBi, and the radiation patterns exhibit good symmetry and wide-beam coverage characteristics.

Multifunctional Double Band Mesh Antenna with Solar Cell Integration for Communications Purposes

A dual band flexible antenna based on a circularly polarized modified meshed patch antenna design. This article focuses on some of the most pressing issues in small satellite applications. The antenna optimization and improvement of antenna performance, such as radiation efficiency. As is well known, circular polarization is immune to the Faraday rotation effect in the ionosphere and can thus prevent a 3-dB loss in geo-satellite communication. With the use of the software program Computer Simulation Technology (CST), the proposed circularly polarized modified meshed patch antenna has been created. Therefore, this article also presents a modified design of a circularly polarized meshed patch antenna to reduce the complexity of the antenna and decrease the size as much as it is capable. However, a meshed patch antenna can support a high communication data rate. The antenna architecture will theoretically be consistent with the installation of solar panels. The antenna utilizes a conductive copper as the core material and the substrate using flexible polyimide. The design antenna is very small, having an overall size of 30 * 30 mm when compared to other conventional non-transparent antenna operating at the same frequencies of 2.6, 3.5 GHz. The antenna that is proposed involves two meshed patch elements of same size but in various shapes. Finally, the proposed antenna is integrated into a solar cell by using the amorphous silicon thin film.

Upconversion/Downshifting Circularly Polarized Luminescence over 1200 nm in a Single Nanoparticle for Optical Anticounterfeiting and Information Encryption.

Multimodal upconversion and downshifting circularly polarized luminescent materials hold significant potential for optical anticounterfeiting applications due to their exceptional chiroptical properties. However, constructing these materials within a single emitter remains challenging. In this study, a conceptual model of multimodal upconversion/downshifting circularly polarized luminescence (CPL) is realized within a single nanoparticle. A new type of nanoparticles with multilayer core-shell architecture is fabricated, capable of delivering upconversion/downshifting luminescence, when excited by a 980 nm laser. Utilizing a co-assembly strategy, multimodal upconversion/downshifting CPL emission, covering a broad emission range from ultraviolet (UV) to the second near-infrared (NIR-II) region, can be realized at the supramolecular level. These chiroptical properties closely follow the chirality of host matrix and are strongly dependent on the distribution mode of nanoparticles within the matrix films. The multimodal upconversion/downshifting CPL behavior enabled cutting-edge encryption applications including optical anticounterfeiting and information encryption. This work introduces a novel approach to designing multimodal upconversion/downshifting CPL materials and opens new avenues for the development of chiroptical functional materials.

Orthogonality of polarization superposition based on polarization holography.

We propose a polarization superposition orthogonal theory based on tensor polarization holography. Based on this theory, the holographic multiplexing capability can be improved measurably. The orthogonality of polarization waves is characterized by the null reconstruction in polarization holography, achieved through the superposition of multiple basic polarization reference waves. This paper analyzes the orthogonality of linear polarization wave superposition and circular polarization wave superposition using the tensor polarization holography theory. Using the polarized holography multiplexing technique, we experimentally verify the orthogonality of polarization wave superposition. Our experimental results align with the theoretical analysis, indicating potential applications in polarization encoding and decoding by this theory, thereby diversifying optical encryption technology Additionally, we demonstrate that polarization superposition orthogonality holds significant promise for optical control technology.

Consolidated Curium Reprocessing Procedure Inspires Molecular Design for Sensitized Curium Circularly Polarized Luminescence.

Curium's stable redox chemistry and ability to emit strong metal-based luminescence make it uniquely suitable for spectroscopic studies among the actinide series. Targeted ligand and coordination compound design can support both fundamental electronic structure studies and industrial safeguards with the identification of unique spectroscopic signatures. However, limited availability, inherent radioactive hazards, and arduous purifications have long inhibited such investigations of this element. A consolidated reprocessing procedure for curium has been developed for the milligram scale. The recovery of not only standard legacy curium samples but also hazardous legacy perchlorate containing curium samples was achieved, culminating in column chromatography utilizing the extraction resin DGA (N,N,N',N'-tetra-2-ethylhexyldiglycolamide, branched). Surprisingly, controlled elution of the Cm band from the extraction resin was followed through bright pink luminescence triggered by an inexpensive hand-held UV-vis lamp (380-400 nm). This observation inspired the design of an enantiopure, C2-symmetrical ligand bearing a chiral (trans-1,2-diaminocyclohexane) backbone with achiral DGA moieties (N,N,N',N'-tetra-n-octylacetamide), that enabled rarely observed curium circularly polarized luminescence upon metal chelation. These combined achievements should unlock more luminescence and circularly polarized luminescence studies of curium, and enable the recovery of many curium and other trivalent actinide samples.

Upconversion/Downshifting Circularly Polarized Luminescence over 1200 nm in a Single Nanoparticle for Optical Anticounterfeiting and Information Encryption

Multimodal upconversion and downshifting circularly polarized luminescent materials hold significant potential for optical anticounterfeiting applications due to their exceptional chiroptical properties. However, constructing these materials within a single emitter remains challenging. In this study, a conceptual model of multimodal up‐conversion/downshifting circularly polarized luminescence (CPL) is realized within a single nanoparticle. A new type of nanoparticles with multilayer core‐shell architecture is fabricated, capable of delivering upconversion/downshifting luminescence, when excited by a 980 nm laser. Utilizing a co‐assembly strategy, multimodal upconversion/downshifting CPL emission, covering a broad emission range from ultraviolet (UV) to the second near‐infrared (NIR‐II) region, can be realized at the supramolecular level. These chiroptical properties closely follow the chirality of host matrix and are strongly dependent on the distribution mode of nanoparticles within the matrix films. The multimodal upconversion/downshifting CPL behavior enabled cutting‐edge encryption applications including optical anticounterfeiting and information encryption. This work introduces a novel approach to designing multimodal upconversion/downshifting CPL materials and opens new avenues for the development of chiroptical functional materials.

Chiral Symmetry Breaking in Colloidal Metal Nanoparticle Solutions by Circularly Polarized Light.

Shape symmetry breaking in the formation of inorganic nanostructures is of significant current interest. It was typically achieved through the growth of colloidal nanoparticles with adsorbed chiral molecules. Photochemical processes induced through asymmetric plasmon excitation by circularly polarized light in surface immobilized nanostructures also led to symmetry breaking. Here, we show that chiral symmetry breaking can be achieved by randomly rotating gold@silver core-shell nanobars in colloidal solution using circularly polarized illumination, where orientational averaging does not eliminate the symmetry breaking of an asymmetric plasmon-induced galvanic replacement reaction. Different morphological effects that are produced by circularly vs linearly polarized light illumination demonstrate the intricate effect of light polarization on the localized plasmonic-induced photochemical response. The essential features of this symmetry breaking, such as illumination wavelength dependence, were reproduced by simulations of circularly polarized light-excited-plasmon-induced hot-electron generation as the source for asymmetric metal deposition. The symmetry breaking becomes smaller in more symmetric geometrical shapes, such as triangular nanoprisms and nanocubes, and down to zero in spherical ones. The degree of symmetry breaking rises when the nanobars are immobilized on a substrate and illuminated from a single direction.

Multibeam focusing using single-layer checkerboard metasurface

ABSTRACT In this study, a novel design methodology of multibeam focusing using a checkerboard metasurface is proposed and investigated. The metasurface is designed as a single-layer anisotropic surface consisting of two identical electric field coupled resonators (ELCRs) separated by a dielectric substrate. When a circularly polarized (CP) wave is incident on the unit cell of the metasurface and the unit cell is rotated to angle of θ, the unit cell has a transmitted phase shift of 2θ. The multibeam transverse and longitudinal focusing and control easily can be achieved by a structural rearrangement of metasurface in the form of a checkerboard without mathematical method. The feasibility of the proposed methodology is confirmed by full-wave simulation and measurement results at 5.8 GHz.

Concentration-Switchable Assembly of Carbon Dots for Circularly Polarized Luminescent Amplification in Chiral Logic Gates and Deep-Red Light-Emitting Diodes.

Stimuli-responsive circularly polarized luminescent (CPL) materials are expected to find widespread application in advanced information technologies, such as 3D displays, multilevel encryption, and chiral optical devices. Here, using R-/S-α-phenylethylamine and 3,4,9,10-perylenetetracarboxylic dianhydride as precursors, chiral carbon dots (Ch-CDs) exhibiting bright concentration-dependent luminescence are synthesized, demonstrating reversible responses in both their morphologies and emission spectra. By adjusting Ch-CD concentration, the switchable wavelength is extended over 180nm (539-720nm), with the maximum quantum efficiency reaching 100%. Meanwhile, upon increasing Ch-CD concentration, the emission wavelength red-shifts, while the chirality of the assembled nanoribbons is synchronously amplified, ultimately achieving CPL at 709nm and a maximum luminescence asymmetry factor of 2.18 × 10-2. These values represent the longest wavelength and the largest glum reported for CDs. Considering the remarkable optical properties of the synthesized Ch-CDs, multilevel chiral logic gates are designed, and their potential practical applications are demonstrated in multilevel anti-counterfeiting encryption, flexible electronic printing, and solid-state CPL. Furthermore, deep-red chiral electroluminescence light-emitting diodes (EL-LEDs) are prepared using these Ch-CDs, achieving an external quantum efficiency of 1.98%, which is the highest value reported to date for CDs in deep-red EL-LEDs, and the first report of chiral electronic devices based on CDs.

Circularly Polarized Light-Induced Chiral Growth of Achiral Plasmonic Nanoparticles Dispersed in a Solution.

Plasmonic nanoparticles (NPs) with chiral geometries have wide applications from chiral molecular sensing to enantioselective catalysis. The synthesis of chiral plasmonic nanoparticles using circularly polarized light (CPL) has attracted a considerable amount of attention because it eliminates the need for chiral molecules. However, NPs need to be immobilized on a solid substrate during synthesis. Here, we successfully synthesized colloidal chiral plasmonic NPs by depositing silver on the surface of achiral gold nanoparticles dispersed in a solution using CPL. Circular dichroism (CD) signals corresponding to the handedness of the irradiated CPL were observed when gold nanorods or gold nanotriangles were used. In contrast, no clear CD signal was observed when gold nanospheres were used. The morphological anisotropy of the gold nanoparticles was a key factor in the synthesis of chiral plasmonic nanoparticles using CPL. Furthermore, we demonstrated the tuning of chiroptical properties according to the CPL wavelength.

A wideband dual-circularly polarized traveling wave dielectric resonator antenna array

ABSTRACT In order to meet the demand of high capacity and high speed transmission of satellite communication system, a wideband dual-circularly polarized dielectric resonator antenna (DRA) array is proposed based on the traveling wave principle. Four DRA elements with slot-coupling excitation are sequentially placed on the ground, and the feeding network is designed to realize the two orthogonal circular polarization radiation waves. A notched copper loop (NCL) around the antenna array is adopted to improve the radiation performance. Depending on the operation of the two ports, the NCL generates the induced currents which rotates clockwise/counterclockwise, increasing the axial ratio bandwidth. In order to further improve the gain stability, the copper sheets are embedded on the top surface of each radiation element, and the copper cylinders perturb the internal field distribution of the DRA to introduce higher-order modes. The measurement results show that the left-hand circular polarization and the right-hand circular polarization operating bandwidths are 11.8% (14.97–16.85 GHz) and 12% (14.91–16.82 GHz). The antenna gain achieves 9.0 dBic. This DRA array can be applied for the vehicle mounted RF terminals in satellite communication.

Metasurface‐based circularly polarised antenna: Enhanced bandwidth with characteristic mode analysis and symmetric branch design

AbstractA low‐profile circularly polarised (CP) metasurface antenna is proposed, utilising characteristic mode analysis (CMA). The antenna design features a two‐layer laminated substrate, a 4×4 Butterfly‐shaped metasurface, a rectangular slot, an irregular transmission line, and a ground plane. The metasurface is analysed using mode significance (MS), characteristic angle (CA), and characteristic current to determine the resonance bandwidth and CA resonance points, which exhibit a near 90° difference. At the intersection of the two MS modes, their CAs differ by nearly 90°, and their far‐field radiation directions align, indicating the potential for achieving circular polarisation at the desired frequency. The integration of the metasurface with the slot antenna is simulated to validate the CMA findings. Additionally, the CP bandwidth is enhanced by modifying the transmission line branches. Measurement of the fabricated antenna reveals an impedance bandwidth (IBW) of 27.4%, a 3‐dB axial ratio bandwidth (ARBW) of 10.1%, and a peak gain of 6.9 dBic at 4.4 GHz. Compared to the design without branches, IBW and ARBW have increased by 10% and 7.3%, respectively.

Ultrathin metasurface for super multi-view 3D display with linear and circular polarization control

Multiview 3D display technologies are advantageous due to their smooth motion parallax, visual discomfort alleviation, and wide depth of focus. However, the potential applications of this technology are constrained by its bulky size and limited light modulation capability. Metasurfaces offer diverse wavefront control by manipulating the phase, amplitude, and polarization of light. They provide design freedom and high image quality for multiview 3D display technologies. Here, we propose an ultrathin metasurface-based super multiview 3D display that can effectively modulate the flexibility of linearly polarized (LP) and circularly polarized (CP) electromagnetic waves. Numerical results demonstrate that it can produce 24 views together for LP and CP waves and high-quality reconstructed 3D images are obtained. The suggested metasurface for super multiview 3D display is promising to underpin the advancement of meta-optics-based operations in 3D display, imaging and integrated optics.

Wideband circularly polarized dielectric resonator antenna with multi-functional metasurface assistance for low profile

ABSTRACT A low-profile broadband circularly polarized (CP) dielectric resonator antenna (DRA) is proposed, utilizing DR reutilization and metasurface (MS) techniques. Two resonant frequencies and an AR minimum are achieved simultaneously, by exciting a rectangular DR with an inclined corner-truncated coupling slot, for it generates nearly degenerated TE111 modes. For significant bandwidth enhancement and low profile, a new resonator is formed by reusing the DR and loading an MS above, which works in orthogonal TM modes. To increase the axial ratio bandwidth (ARBW) further without enlarging the antenna size， two parasitic patches are printed on two adjacent side walls of the DR. To verify the rationality and feasibility, the antenna is fabricated and measured. The fabricated prototype possesses the profile of 0.06λ 0 (λ 0 is the free-space wavelength at the center frequency). The measured impedance bandwidth (IBW) and ARBW are 36.05% (4.23 ~ 6.09 GHz) and 22.46% (4.9 ~ 6.14 GHz), respectively. The proposed antenna has both broadband characteristics and a low profile, making it easy to integrate into space-limited wireless communication systems with high data rates.