Circularly Polarized Research Articles

Defective ground structure loaded polarization reconfigurable ring-shaped patch antenna for multiband applications

ABSTRACT A novel stub-loaded polarization-reconfigurable ring-shaped circular patch antenna designed for multi-band operation and switchable polarization is presented, having advantages such as ease in manufacturing and compact size (20 mm × 20 mm). The circular ring is segmented into four sectors, and two stubs are loaded on the inner side of the ring to disrupt the current distribution and create two orthogonal electric field vectors, generating circular polarization. The antenna supports it in switching three distinct polarization states: linear polarization, left-hand circular polarization, and right-hand circular polarization, selectable with different combinations of diodes. From the measured results, ARBW (<3 dB) is 32.12% and 6.06% for CP bands. Additionally, eight LP bands with IBW of 71.66%, 3.55%, 3.94%, 35.88%, 45%, 45.5%, 34.77%, and 8.2% are achieved. The antenna exhibits satisfactory stable gain across all frequency bands and excellent radiation performance, making it a promising candidate for modern wireless communication applications (C-band, ITS2 fixed, X-band, and Ku-band satellite downlink operations).

Structural transitions of ionic microgel solutions driven by circularly polarized electric fields.

In this work, a theoretical approach is developed to investigate the structural properties of ionic microgels induced by a circularly polarized (CP) electric field. Following a similar study on chain formation in the presence of linearly polarized fields [T. Colla et al., ACS Nano, 2018, 12, 4321-4337], we propose an effective potential between microgels which incorporates the field-induced interactions via a static, time averaged polarizing charge at the particle surface. In such a coarse-graining framework, the induced dipole interactions are controlled by external parameters such as the field strength and frequency, ionic strength, as well as microgel charge and concentration, thus providing a convenient route to induce different self-assembly scenarios through experimentally adjustable quantities. In contrast to the case of linearly polarized fields, dipole interactions in the case of CP light are purely repulsive in the direction perpendicular to the polarization plane, while featuring an in-plane attractive well. As a result, the CP field induces layering of planar sheets arranged perpendicularly to the field direction, in strong contrast to the chain formation observed in the case of linear polarizations. Depending on the field strength and particle concentration, in-plane crystallization can also take place. Combining molecular dynamics (MD) simulations and the liquid-state hypernetted-chain (HNC) formalism, we herein investigate the emergence of layering formation and in-plane crystal ordering as the dipole strength and microgel concentration are changed over a wide region of parameter space.

Circularly polarized dual-band resonance in a miniaturized implantable antenna using combined hexagonal and rhombic patches

The design and characterisation of a novel dual-band implantable antenna with compact size is presented in this research. The antenna, which is in size and operates at two critical frequencies—0.954 GHz in the UHF band and 2.4 GHz in the ISM band—was fabricated on an RT6010 substrate. The U-shaped slot and shorting pin on the radiating element have been exploited to achieved dual-band and circular polarization. The antenna is noteworthy for achieving circular polarization with a broad axial ratio bandwidth of 24.6%, which enables strong performance throughout its operating frequencies. The proposed antennas SAR values satisfy IEEE safety standards for implantable medical devices with a gain of − 28.1 dB at 2.4 GHz and − 31.2 dB at 0.954 GHz, despite its small size. The design represents a significant advancement in the field of medical implant technology since it prioritizes effective wireless communication capabilities while upholding strict safety regulations.

Micromagnetic simulations of magnon-magnon coupling in synthetic antiferromagnets with tilted magnetic anisotropy.

Hybrid magnonics has attracted extensive attention for its potential applications in quantum information processing, especially following the discovery of strong coupling in magnon-magnon hybrid systems. In this paper, we studied the coupling phenomena between the left-handed (LH) and right-handed (RH) magnon modes in synthetic antiferromagnets (SAFs) with a tilted perpendicular magnetic anisotropy (PMA). By tilting the PMA at a certain angle from the film normal, we achieved strong magnon-magnon coupling without the need for an external magnetic field. The resulting hybrid eigenmodes exhibit characteristics of a linear combination of pure LH and RH modes. In addition, micromagnetic simulations revealed in detail the gradual change of hybrid resonance modes from linear to elliptic, and eventually to circular polarization as the coupling strength gradually decreases. We also examined the effects of an applied magnetic field on the coupling strength and mechanism between the two eigenmodes. These findings provide valuable insights into magnetic dynamics within hybrid magnonic systems for spintronic applications involving magnon polarization.&#xD.

Axially Chiral TADF Imidazolium Salts for Circularly Polarized Light‐Emitting Electrochemical Cells

A pair of axially chiral thermally activated delayed fluorescent (TADF) enantiomers, R‐TCBN‐ImEtPF6 and S‐TCBN‐ImEtPF6, with intrinsic ionic characteristics were efficiently synthesized by introducing imidazolium hexafluorophosphate to chiral TADF unit. The TADF imidazolium salts exhibited a high photoluminescence quantum yield (PLQY) of up to 92%, a small singlet–triplet energy gap (∆EST) of 0.04 eV, as well as reversible redox properties. Furthermore, the enantiomers showed distinct mirror‐image CD and CPL activities with glum values of ‐3.7×10‐3 and +3.4×10‐3. Notably, by doping the axial TADF imidazolium salts into achiral TADF sensitizer, sandwich‐structured light‐emitting electrochemical cells (LECs) without the addition of ionic liquids (ILs) or ionic transition‐metal compounds (iTMCs) were fabricated. When driven at 50 A m‐2, the LECs displayed an EQE of up to 5.2% and strong circularly polarized electroluminescence (CPEL) with gEL values of +3.3×10‐3 and ‐3.0×10‐3. This represents the first CP‐LEC based on TADF materials and offers a promising strategy for the development of high‐performance CPEL devices.

Axially Chiral TADF Imidazolium Salts for Circularly Polarized Light-Emitting Electrochemical Cells.

A pair of axially chiral thermally activated delayed fluorescent (TADF) enantiomers, R-TCBN-ImEtPF6 and S-TCBN-ImEtPF6, with intrinsic ionic characteristics were efficiently synthesized by introducing imidazolium hexafluorophosphate to chiral TADF unit. The TADF imidazolium salts exhibited a high photoluminescence quantum yield (PLQY) of up to 92%, a small singlet-triplet energy gap (∆EST) of 0.04 eV, as well as reversible redox properties. Furthermore, the enantiomers showed distinct mirror-image CD and CPL activities with glum values of -3.7×10-3 and +3.4×10-3. Notably, by doping the axial TADF imidazolium salts into achiral TADF sensitizer, sandwich-structured light-emitting electrochemical cells (LECs) without the addition of ionic liquids (ILs) or ionic transition-metal compounds (iTMCs) were fabricated. When driven at 50 A m-2, the LECs displayed an EQE of up to 5.2% and strong circularly polarized electroluminescence (CPEL) with gEL values of +3.3×10-3 and -3.0×10-3. This represents the first CP-LEC based on TADF materials and offers a promising strategy for the development of high-performance CPEL devices.

Rigidly Locked Pyrene Excimers in Planar Chiral Pyrenophanes for Intense and Stable Circularly Polarized Photoluminescence and Electrochemiluminescence

Aiming at the construction of novel platforms with excellent performances in both circularly polarized photoluminescence (CP‐PL) and electrochemiluminescence (CP‐ECL), a new family of pyrenophanes with rigidly locked pyrene dimers and varied bridges has been designed and synthesized. Attributed to densely packed pyrene excimers, the resultant pyrenophanes revealed tunable bridge‐dependent emission behaviors, as investigated by femtosecond time‐resolved transient absorption spectroscopy. More importantly, all these planar chiral pyrenophanes display strong CP‐PL with large dissymmetry factor (gPL) values up to 0.034, and such excellent performances remain stable in a wide range of solvents, temperatures, and concentrations. Attractively, the highest gECL values up to 0.014 reported so far has been achieved for the CP‐ECL emissions of the chiral pyrenophanes. Attributed to their unique structural features and outstanding CPL performances, these novel pyrenophanes could serve as promising platforms for both fundamental investigations on pyrene excimers and practical applications such as chiral sensing.

Rigidly Locked Pyrene Excimers in Planar Chiral Pyrenophanes for Intense and Stable Circularly Polarized Photoluminescence and Electrochemiluminescence.

Aiming at the construction of novel platforms with excellent performances in both circularly polarized photoluminescence (CP-PL) and electrochemiluminescence (CP-ECL), a new family of pyrenophanes with rigidly locked pyrene dimers and varied bridges has been designed and synthesized. Attributed to densely packed pyrene excimers, the resultant pyrenophanes revealed tunable bridge-dependent emission behaviors, as investigated by femtosecond time-resolved transient absorption spectroscopy. More importantly, all these planar chiral pyrenophanes display strong CP-PL with large dissymmetry factor (gPL) values up to 0.034, and such excellent performances remain stable in a wide range of solvents, temperatures, and concentrations. Attractively, the highest gECL values up to 0.014 reported so far has been achieved for the CP-ECL emissions of the chiral pyrenophanes. Attributed to their unique structural features and outstanding CPL performances, these novel pyrenophanes could serve as promising platforms for both fundamental investigations on pyrene excimers and practical applications such as chiral sensing.

Vectorial acousto-optic Raman–Nath diffraction effect of chiral liquid media

The acousto-optic Raman–Nath (RN) diffraction effects of vector beams diffracted by the chiral ultrasonic grating are demonstrated experimentally and theoretically. The deviation of left- and right-handed circularly polarized components in higher-order diffraction light leads to the rearrangement of their polarization states and intensity due to the different refractive indices of left- and right-hand circularly polarized lights. When the difference between the refractive indices for left- and right-hand circular polarizations is small, linear polarization components of the higher-order diffraction light with the input localized linearly polarized vector optical field rotate compared to the zero-order diffraction light. Novel, to the best of our knowledge, intensity distributions of linear polarization components appear for the input hybridly polarized vector beam.

Nucleation-Controlled Crystallization of Chiral 2D Perovskite Single Crystal Thin Films for High-Sensitivity Circularly Polarized Light Detection.

2D Dion-Jacobson (DJ) chiral perovskite materials exhibit significant promise for developing high-performance circularly polarized light (CPL) photodetectors. However, the inherently thick nature of DJ-phase 2D perovskite single crystal limits their ability to differentiate CPL photons with the two opposite polarization states. In addition, the growth of DJ-phase perovskite single crystal thin films (SCTFs) has proven challenging due to the strong interlayer electronic coupling. Here, a nucleation-controlled strategy is employed to grow a novel DJ-phase perovskite [(R/S)-3APr]PbI4 [(R/S)-3APr = (R/S)-3-Aminopyrrolidine] SCTFs with large area, low thickness and hence high aspect ratios. Structural and photoluminescence analyses reveal that introducing the divalent organic cations into the perovskite framework reduce the interlayer distance, resulting in low exciton binding energy. This facilitates charge separation and transport. The resulting SCTF photodetector showcases excellent detection performance with anisotropy factor for photocurrent as high as 0.65, responsivity of 1.97 A W-1, detectivity of 5.3 × 1013 Jones, and 3-dB frequency of 2940Hz, demonstrating its potential as a promising candidate for CPL-sensitive photodetectors. This novel approach, therefore, provides a framework for the growth of DJ-phase perovskite SCTFs and advances their applications in sensitive CPL photodetection.

Topologically Streamlined Single Feed Wide Band Circular Polarized Antenna

A single feed circularly polarized (CP) microstrip hexagonal open loop monopole antenna with defective ground plane is introduced in this article. The antenna is made up of an open hexagonal loop excited by a 50Ω microstrip feed line, ground defected by a curved structure with two slots and a “U” shaped slit etched below the microstrip feed line. The optimized designs are verified experimentally for reflection coefficient, axial ratio bandwidth, realized gain and radiation patterns. Results of the measurement indicate that the proposed antenna attains a wide impedance bandwidth of 103% (2.5–7.8 GHz), axial ratio bandwidth of 83% (2.9–7 GHz) and peak gain of 3.5 dBi. The proposed radiator’s novelty stems from the blend of uncomplicated geometry and single-point-fed excitation with broadband CP characteristics having a compact size of only 0.149λ0 at the lowest CP frequency. The suggested antenna is an appropriate one for various wireless communication applications like WLAN, Wi-MAX, Aeronautical Radio Navigation band and C band applications. Exhaustive studies indicate superior performance of the suggested antenna as compared with the state-of-the art designs.

Stomatopods compound eye structure-inspired circular polarization quantum well infrared photodetectors

Stomatopods compound eye structure-inspired circular polarization quantum well infrared photodetectors

A wide band circularly polarized antenna using meta surface for Wi-Fi applications

Abstract A circularly polarized, single-feed, low-profile patch antenna with enhanced gain and bandwidth for WI –FI applications is presented in this paper. The proposed antenna has a slot-loaded square patch (SLSP) is placed between reactive impedance structure (RIS)-based metasurface (MS) and the ground plane. A 6x6 circular RIS metasurface is used to improve the gain, impedance and axial ratio bandwidth. The antenna prototype’s overall dimensions are 60mm x 60mm x 3.6mm.The measured impedance bandwidth (IBW) of the proposed antenna is 26% (4.98GHz–6.48GHz) which covers the 5GHz (5.150-5.850 GHz) and 6GHz (5.950 – 7.125 GHz) frequency bands of wireless spectrum. The antenna exhibits right hand circular polarization with maximum measured gain of 6.5 dBic and the 3-dB ARBW is 5.23% (5.47GHz–5.77GHz).&amp;#xD;

An Underwater Polarization Imaging Technique Based on the Construction and Decomposition of the Low-Rank and Sparse Matrix in Stokes Space for Polarization State Imaging

Traditional underwater polarization imaging methods can only provide clear degree of polarization (DOP) and intensity images of the object but cannot provide images of the polarization state of the object. This paper proposes a method to extract clear object information from turbid water in all four Stokes parameter (I, Q, U, and V) channels by using the full Stokes camera, enabling clear polarization state image reconstruction. The method utilizes multiple images from different angles to construct a low-rank and sparse matrix. Then, by decomposing this matrix into sparse and low-rank components, clear Q, U, and V images (i.e., the full polarization state) can be obtained. Unlike traditional methods that assume the circularly polarized component (V component) to be zero, this method retains V channel information, allowing for circular polarization component measurement. The study successfully reconstructed clear underwater images of samples with inhomogeneous DOP distribution and obtained the clear polarization states of polarizers and fish in the turbid water. The results show that the proposed method can visualize and analyze the object’s polarization state quantitatively with high accuracy in turbid water for the first time, potentially extending the applicability of polarization underwater imaging in ocean exploration.

Dual Circularly Polarized Luminescence with Controllable Polarizations in a Single Cholesteric Liquid Crystal

Dual Circularly Polarized Luminescence with Controllable Polarizations in a Single Cholesteric Liquid Crystal

Contrasting Mechanochromic Luminescence of Enantiopure and Racemic Pyrenylprolinamides: Elucidating Solid‐State Excimer Orientation by Circularly Polarized Luminescence

AbstractCircularly polarized luminescence (CPL) and mechanochromic luminescence (MCL) have independently made substantial progress in recent years. However, the exploration of MCL in solid‐state CPL materials, which holds practical significance, is still in its infancy. Herein, we report the MCL properties of readily accessible chiral pyrenylprolinamides bearing tert‐butoxycarbonyl (Boc) or 2,2,2‐trichloroethoxycarbonyl (Troc) groups. Enantiopure crystals of the Boc derivative display a greater MCL wavelength shift than racemic crystals, while the Troc derivative exhibit the opposite trend. Most notably, the enantiopure crystals show mechanochromic CPL. Unlike in previous examples, where CPL is quenched upon amorphization, robust CPL spectra were observed even in the amorphous states. By applying the excimer chirality rule, we have, for the first time, acquired insights into the excited‐state structures within mechanically generated amorphous states. These findings offer a novel design strategy for developing mechanochromic CPL materials, paving the way for the future advancements in this emerging field.

Contrasting Mechanochromic Luminescence of Enantiopure and Racemic Pyrenylprolinamides: Elucidating Solid-State Excimer Orientation by Circularly Polarized Luminescence.

Circularly polarized luminescence (CPL) and mechanochromic luminescence (MCL) have independently made substantial progress in recent years. However, the exploration of MCL in solid-state CPL materials, which holds practical significance, is still in its infancy. Herein, we report the MCL properties of readily accessible chiral pyrenylprolinamides bearing tert-butoxycarbonyl (Boc) or 2,2,2-trichloroethoxycarbonyl (Troc) groups. Enantiopure crystals of the Boc derivative display a greater MCL wavelength shift than racemic crystals, while the Troc derivative exhibit the opposite trend. Most notably, the enantiopure crystals show mechanochromic CPL. Unlike in previous examples, where CPL is quenched upon amorphization, robust CPL spectra were observed even in the amorphous states. By applying the excimer chirality rule, we have, for the first time, acquired insights into the excited-state structures within mechanically generated amorphous states. These findings offer a novel design strategy for developing mechanochromic CPL materials, paving the way for the future advancements in this emerging field.

Reversible Ferroelectric Polarization Modulation of Chiral Molecular Ferroelectrics by Circularly Polarized Light.

The optical modulation of ferroelectric polarization constitutes a transformative, non-contact strategy for the precise manipulation of ferroelectric properties, heralding advancements in optically stimulated ferroelectric devices. Despite its potential, progress in this domain is constrained by material limitations and the intricate nature of the underlying mechanisms. Recent studies have achieved efficient regulation of ferroelectric polarization and thermal conductivity in chiral ferroelectric thin films through the application of left- and right-handed circularly polarized light (LCP and RCP). Differential absorption of circularly polarized light (CPL) induces nonequilibrium carrier dynamics, generating distinctive interfacial electrostatic fields that enable precise control of ultrathin ferroelectric films. For (R)-BINOL-DIPASi and (S)-BINOL-DIPASi (C26H26O2Si), polarization changes surpass 23%, exhibiting opposite response under LCP and RCP excitation. In R chiral films, remnant polarization decreases from 1.05 µCcm- 2 under LCP to 0.85 µCcm- 2 under RCP, whereas in S chiral films, polarization increases from 0.85 µCcm- 2 under LCP to 0.98 µCcm- 2 under RCP. This reversible modulation facilitates reliable switching between ON and OFF states, presenting the potential of chiral ferroelectric materials for flexible, high-speed integrated photonic sensor technologies.

Controlling of Circularly Polarized Luminescence via Modulating the Angle Between Transition Electric and Magnetic Dipole Moments

AbstractThe most challenging task in the development of chiral luminescent materials is currently increasing the dissymmetry factors (gPL, gEL) of circularly polarized luminescence (CPL). Current research primarily focuses on enhancing the molecular transition magnetic dipole moment, while the angle between the transition electric and magnetic dipole moment (θe,m) has received comparatively limited attention. In this study, two pairs of intrinsically axial chiral fluorescence (CP‐MR‐F) and thermally activated delayed fluorescence (CP‐MR‐TADF) enantiomers (R/S‐BBCz‐BN and R/S‐OBBCz‐BN) with increased g factors by modulating θe,m are reported. Based on R/S‐5H,5′H ‐6,6′‐bibenzo[b]carbazole units, the theoretically calculated θe,m and gcal for S‐BBCz‐BN are 17.7° and 1.1 × 10−2, respectively, enabling excellent CPL properties with |gPL| of 5.8 × 10−3 in toluene, representing one of the highest g values among MR materials. By employing the less conjugated R/S‐7,7′,8,8′,9,9′,10,10′‐octahydro‐5H,5′H‐6,6′‐bibenzo[b]carbazole groups with better electron donating ability, R/S‐OBBCz‐BN demonstrate good MR‐TADF and CPL properties with a peak at 467 nm, a full width at half‐maximum of 27 nm, and |gPL| of 2.5 × 10−3. Furthermore, the optimized circularly polarized organic light‐emitting diodes based on these two pairs of enantiomers showcase high maximum external quantum efficiencies of 24.7%/33.3% and mirror symmetrical circularly polarized electroluminescence with |gEL| factors of 3.4/1.2 × 10−3, respectively.

A 3D-Printed Enclosed Twist Dielectric Resonator Antenna with Circular Polarization

A 3D-Printed Enclosed Twist Dielectric Resonator Antenna with Circular Polarization