Circularly Polarized Research Articles

Shape-Persistent Tetraphenylethylene Macrocycle: Highly Efficient Synthesis and Circularly Polarized Luminescence

Circularly polarized luminescence (CPL) is an emerging field with significant applications in molecular electronics, optical materials, and chiroptical sensing. Achieving efficient CPL emission in organic systems remains a major challenge, particularly in the development of materials with high fluorescence quantum yields (ΦF) and large luminescence dissymmetry factors (glum). Herein, we report the efficient synthesis of shape-persistent tetraphenylethylene macrocycles and investigate its potential as a CPL material. Chiral side chains were introduced to induce chiroptical properties. The macrocycles and their properties were characterized using NMR, MALDI-TOF MS, FT-IR, TGA, DSC, UV-Vis spectroscopy, SEM, fluorescence spectroscopy, ECD, and CPL. A significant fluorescence enhancement was observed upon aggregation, demonstrating a typical aggregation-induced emission (AIE) behavior. Moreover, one of the macrocycles in the solid state displayed distinct CPL emission with a high glum of 2 × 10−2 and a ΦF value reaching 60%, and exhibited aggregation-induced circularly polarized luminescence (AICPL). These findings highlight the advantage of using a macrocycle with a noncollapsible backbone for the design of organic systems with CPL property, offering promising applications in chiroptical materials.

Strong signature of right-handed circularly polarized photoionization close to the cyclotron line in the atmosphere of magnetic white dwarfs

Magnetic fields break the symmetry of the interaction of atoms with photons with different polarizations, yielding chirality and anisotropy properties. The dependence of the absorption spectrum on the polarization, a phenomenon known as dichroism, is present in the atmosphere of magnetic white dwarfs. Its evaluation for processes in the continuum spectrum has been elusive so far due to the absence of appropriate ionization equilibrium models and incomplete data on photoionization cross sections. We combined rigorous solutions to the equilibrium of atomic populations with approximate cross sections to calculate the absolute opacity due to photoionization in a magnetized hydrogen gas. We predict a strong right-handed circularly polarized absorption (χ+) formed blueward of the cyclotron resonance for fields from about 14 to several hundred megagauss. In energies lower than the cyclotron fundamental, this absorption shows a deep trough with respect to linear and left-handed circular polarizations that steepens with the field strength. The jump in χ+ is due to the confluence of a large number of photoionization continua produced by right-handed circularly polarized transitions from atomic states with a nonnegative magnetic quantum number toward different Landau levels.

Near-Infrared Magnetic Circularly Polarized Luminescence and Slow Magnetic Relaxation in a Tetrazinyl-Bridged Erbium Metallocene.

The magnetic and magneto-optical properties of a tetrazinyl radical-bridged ErIII metallocene, [(Cp*2ErIII)2(bpytz•-)][BPh4] (1; Cp* = pentamethylcyclopentadienyl, bpytz = 3,6-bis(3,5-dimethyl-pyrazolyl)-1,2,4,5-tetrazine), are reported. As confirmed by these studies strong Ln-rad coupling is achieved, with 1 exhibiting slow magnetic relaxation under a 1000 Oe dc field. The optical and magneto-optical profile of 1 is completed by both near-infrared (NIR) luminescence and magnetic circularly polarized luminescence (MCPL), representing the first example of NIR MCPL with ErIII.

Multimode resonant microstrip antennas with electrically small patch and frequency scannable circularly polarised angle

AbstractSemi‐analytical design approach to electrically small, dual‐mode resonant, wideband circularly polarised (CP) microstrip annular sector patch antenna (MASPA) with variable polarization is proposed for satellite‐assisted Internet‐of‐vehicle (IoV). At first, the upper bound of electrically small patch is theoretically laid down by advancing an interpolated algorithm to the eigen‐roots of the characteristic equation, so that the radius of patch can be rapidly determined in the initial design step. In this way, MASPA with electrically small patch, multimode resonant, and frequency scannable CP angle can be yielded. Dual‐mode resonant MASPAs with flare angles of 330° on air substrate, and 270° on suspended microstrip air/F4B substrates having a profile less than 0.05‐wavelength are then numerically studied and experimentally validated. In the suspended microstrip case, MASPA with maximum patch radius of 0.159‐wavelength (electrically small), equal impedance and tilted CP bandwidths up to 26.6%, and tilted CP angle of θt = −10°–35°, has been successfully implemented. Therefore, the proposed approach should be highly effective for low‐profile, electrically small, wideband CP antenna designs.

Reversal of chirality in solutions and aggregates of chiral tetrachlorinated diperylene diimides towards efficient circularly polarized light detection.

Helicenes exhibit promise as active layer materials for circularly polarized light (CPL) detectors due to their strong chiroptical activity. However, their practical application is limited by the complicated synthesis and loosely solid-state packing. This study introduces a chiral induction strategy towards the synthesis of helicene derivatives, chiral tetrachlorinated diperylene diimides ((SSSS)-4CldiPDI or (RRRR)-4CldiPDI). When incorporating the chiral (S/R)-1-cyclohexylethyl (Cy) substituents, the chirality is directly transferred to the π-aromatic core and forms the PP- or MM-helicene subunit. Notably, (SSSS)-Cy induces preferred PP helicity while (RRRR)-Cy leads to the MM helicity in the monomers. However, these molecules exhibit reversed chirality in crystals, where (SSSS)-Cy controls MM helicity and (RRRR)-Cy induces PP helicity. Theoretical calculations reveal that the (SSSS)-PP structure demonstrates lower energy distribution in monomers, whereas the (SSSS)-MM structure exhibits lower energy in crystals. Then, the CPL detection based on n-type PDI-helicene derivatives is achieved by using (SSSS)-4CldiPDI or (RRRR)-4CldiPDI crystals. The maximum photocurrent dissymmetry factor gph of +0.16 for (RRRR)-4CldiPDI and -0.15 for (SSSS)-4CldiPDI is obtained. Our work demonstrates a novel chiral induction strategy for designing helicene-based materials with both high dissymmetry factor and large charge carrier mobility, which offers great potential for the advancement of CPL detection.

Mechanical and thermal responsive chiral photonic cellulose hydrogels for dynamic anti-counterfeiting and optical skin.

Dynamic responsive structural colored materials have drawn increased consideration in a wide range of applications, such as colorimetric sensors and high-safety tags. However, the sophisticated interactions among the individual responsive parts restrict the advanced design of multimodal responsive photonic materials. Inspired by stimuli-responsive color change in chameleon skin, a simple and effective photo-crosslinking strategy is proposed to construct hydroxypropyl cellulose (HPC) based hydrogels with multiple responsive structured colors. By controlling UV exposure time, the structural color of HPC hydrogels can be effectively controlled in a full-color spectrum. At the same time, HPC hydrogels showcase temperature and mechanical dual-responsive structural colors. In particular, the microstructure of HPC hydrogels undergoes a transition from the chiral nematic phase to the nematic phase under the action of external stretching, leading to a significant reflection of circularly polarized light (CPL) to linearly polarized light (LPL). Given the diverse responsiveness exhibited by HPC hydrogels and their unique structural transition properties under external forces, we have explored their potential applications as dynamic anti-counterfeiting labels and optical skins. This work reveals the great possibility of using structural colored cellulose hydrogels in multi-sensing and optical displays, opening up a new path for the exploration of next-generation flexible photonic devices.

Wideband Circularly Polarized Conformal Dielectric Resonator Antenna for High Gain Applications

ABSTRACTA compact and circularly polarized convex dielectric resonator antenna (CDRA) is investigated in this communication. Eigenmode method is used to analyze electromagnetic field propagation and resonant frequency of the antenna. Benefits of conformal structure over a planar surface are mentioned. A pair of vertical slots are introduced on the ground plane to produce orthogonal degenerate modes. Finally, the proposed curved DRA provides a fractional impedance bandwidth of 22%, axial ratio bandwidth of 11.27% and a stable gain of more than 5 dBi over the desired passband with a peak gain of 7 dBi. To validate the simulated results, a prototype is fabricated and measured.

Unified Design of Dual-Band and Tri-Band Dual-Sense Circularly Polarized Patch Antennas under Quad-Mode Operation

Unified Design of Dual-Band and Tri-Band Dual-Sense Circularly Polarized Patch Antennas under Quad-Mode Operation

A Compact Dual Port Circularly Polarized MIMO Antenna for On-/Off-Body WBAN Applications

A Compact Dual Port Circularly Polarized MIMO Antenna for On-/Off-Body WBAN Applications

Broadband Circularly Polarized Crossed Dipole Antenna Loaded with Magneto-electric Dipole

Broadband Circularly Polarized Crossed Dipole Antenna Loaded with Magneto-electric Dipole

A Lightweight Flexible Wearable Circularly Polarized Antenna for Navigation and Positioning in IoT Applications

A Lightweight Flexible Wearable Circularly Polarized Antenna for Navigation and Positioning in IoT Applications

Efficiency Analysis of Parasitic Common and Differential Modes for Ultrathin Circularly Polarized Microstrip Antenna

Efficiency Analysis of Parasitic Common and Differential Modes for Ultrathin Circularly Polarized Microstrip Antenna

Low‐profile circular‐polarized fractal antenna design with reduced orbital angular momentum beam divergence

AbstractThe authors introduce a novel low‐profile circular‐polarized three‐layer fractal antenna design to reduce beam divergence in orbital angular momentum (OAM) applications at microwave frequencies. The top layer of the proposed design has a printed Koch fractal antenna that is coupled to a rotated rectangular patch antenna in the mid‐layer fed through a microstrip line. The bottom layer consists of a metallic ground plane to improve beam collimation. The antenna was developed from a new fractal geometry generated in Scilab™. Characteristic mode theory was used in the antenna design to obtain two orthogonal current modes in quadrature that generate circular polarization with OAM fields of order l = –1 at 5.88 GHz. The proposed fractal antenna system has good potential to improve the performance of microwave OAM systems.

A Wideband Differential Dual Circularly Polarized Laminated Resonator Antenna

A Wideband Differential Dual Circularly Polarized Laminated Resonator Antenna

Controlling Sign and Magnitude of Circularly Polarized Luminescence of Axially Chiral Schiff-Base Boron Difluoride Complexes Bearing Polyethylene Glycol Chains.

The synthesis, structure, and circularly polarized luminescence (CPL) properties of axially chiral boron difluoride complexes are described. A series of optically pure bis (boron difluoride) complexes were prepared in 5 steps from commercially available (S)- or (R)-BINOL as starting materials. The complexes were found to exhibit similar yellow photoluminescence in solution, regardless of the type of substituents on the nitrogen atoms. Notably, for the complex with polyethylene glycol chains, homogeneous and transparent films were formed by the drop-cast method, showing intense CPL with a different sign from that of the solution state. Density functional theory (DFT) calculations were performed to understand their photophysical behavior including configuration-dependent CPL properties.

Wearable Broadband Circularly Polarized Antenna with Characteristic Mode Analysis for Wireless Body Area Network Applications

Wearable Broadband Circularly Polarized Antenna with Characteristic Mode Analysis for Wireless Body Area Network Applications

Dual Circularly Polarized Metasurface Antenna Based on Inward and Outward Surface Wave Duplexing

Dual Circularly Polarized Metasurface Antenna Based on Inward and Outward Surface Wave Duplexing

High Scanning Rate Circularly Polarized Dual-beam Frequency Scanning Antenna based on Orthogonal Cosine-type SSPP

High Scanning Rate Circularly Polarized Dual-beam Frequency Scanning Antenna based on Orthogonal Cosine-type SSPP

A Broadband Circularly Polarized Patch Antenna Array with Oblique Beam for Satellite Wide Scanning Coverage Applications

A Broadband Circularly Polarized Patch Antenna Array with Oblique Beam for Satellite Wide Scanning Coverage Applications

Broadband Linear to circular polarization conversion over extreme angle of view using a single layer Frequency selective surface

Broadband Linear to circular polarization conversion over extreme angle of view using a single layer Frequency selective surface