Circularly Polarized Research Articles

5]Helicene Based π‐Conjugated Macrocycles with Persistent Figure‐Eight and Möbius Shapes: Efficient Synthesis, Chiral Resolution and Bright Circularly Polarized Luminescence

π‐Conjugated chiral shape‐persistent molecular nanocarbons hold great potential as chiroptical materials, though their synthesis remains a considerable challenge. Here, we present a simple approach using Suzuki coupling of a [5]helicene building block with various aromatic units, enabling the one‐pot synthesis of a series of chiral macrocycles with persistent figure‐eight and Möbius shapes. Single‐crystal structures of 7 compounds were solved, and 22 enantiomers were separated by preparative chiral HPLC. A notable pyrene‐bridged figure‐eight macrocycle, with its rigid, fully π‐conjugated and overcrowded structure, exhibited pure excimer emission and outstanding circularly polarized luminescence (CPL) properties, including a large dissymmetric factor (|glum| = 3.8 × 10−2) and significant CPL brightness (BCPL = 710.5 M‐1cm‐1). This method provides a versatile synthetic platform for producing various chiral D2‐symmetric figure‐eight macrocycles and singly or triply twisted Möbius macrocycles with C2 and D3 symmetry, offering tunable chiroptical properties for CPL applications.

Learning‐Based Vectorial Reconstruction of Orthogonal Polarization Components in a Structured Vector Optical Field Passing Through Scattering Media

AbstractOptical imaging through scattering media has become important due to its fundamental physics interest and various applications. The reconstruction of a structured optical field with various states of polarization passing through a scattering medium with a speckle pattern behind the scattering medium remains challenging since existing restoring techniques only reconstruct the speckle in a single‐polarization state (scalar optical field). This work proposes a novel approach to simultaneously restore the initial orthogonally polarized components from a speckle pattern behind a scattering medium. The neural network Polarization‐DenseUnet (P‐DenseUnet) based on the vector transfer matrix is constructed to restore the two orthogonally linear (or circular) polarization components of a structured vector optical field from a speckle pattern behind the scattering medium. The generalization and effectiveness of this proposed method are tested for high fidelity with different phase distributions such as vortex, digits, and Fashion‐mnist.

Metasurface inspired printed dual‑port MIMO antenna system with LP to CP conversion features for millimeter wave n260 band applications.

A cutting-edge antenna system has been developed for new radio (NR) millimeter wave operating from 36.0 to 40.0GHz frequency range 2 (FR 2) n260 band applications. This innovative system incorporates metasurface-inspired printed dual-port MIMO technology, which includes LP to CP conversion features. The positional orientation of the elements of the MIMO antenna with stacked metasurface provoked the spatial diversity. To convert linearly polarised (LP) waves to circularly polarised (CP) waves, the metasurface layer is suspended above the MIMO antenna. LP to CP polarisation conversion occurs when the conducting strip and rectangular space between strips on the substrate generate π/2 phase-shifted electric field components (Ex and Ey). The proposed stepped impedance-fed antenna elements and metasurface are fabricated on commercially available high-frequency laminates using a double-layer printed circuit board (PCB) fabrication facility. The test findings exhibit a satisfactory level of concurrence with the calculated/measured findings regarding scattering parameters, diversity performance parameters, and realized gain. The result is a highly efficient and versatile antenna system that is ideal for advanced engineering applications.

Coassembled Ionic Organic Microcrystals with Bright Circularly Polarized Luminescence

Coassembled Ionic Organic Microcrystals with Bright Circularly Polarized Luminescence

MeerKAT observations of pair-plasma induced birefringence in the double pulsar eclipses

ABSTRACT PSR J0737−3039A/B is unique among double neutron star systems. Its near-perfect edge-on orbit causes the fast spinning pulsar A to be eclipsed by the magnetic field of the slow spinning pulsar B. Using high-sensitivity MeerKAT radio observations combined with updated constraints on the system geometry, we studied the impact of these eclipses on the incident polarization properties of pulsar A. Averaging light curves together after correcting for the rotation of pulsar B revealed enormous amounts of circular polarization and rapid changes in the linear polarization position angle, which occur at phases where emission from pulsar A is partially transmitted through the magnetosphere of pulsar B. These behaviours confirm that the eclipse mechanism is the result of synchrotron absorption in a relativistic pair-plasma confined to the closed-field region of pulsar B’s truncated dipolar magnetic field. We demonstrate that changes in circular polarization handedness throughout the eclipses are directly tied to the average line of sight magnetic field direction of pulsar B, from which we unambiguously determine the complete magnetic and viewing geometry of the pulsar.

Interplay of Excited‐States on Circularly Polarized Thermally Activated Delayed Fluorescent Chiral Exciplexes

Interplay of Excited‐States on Circularly Polarized Thermally Activated Delayed Fluorescent Chiral Exciplexes

Cholesteric Liquid Crystal Polymer Networks Doped with an Axially Chiral Fluorescent Dye: Circularly Polarized Luminescence and Anti‐Counterfeiting Applications

Cholesteric Liquid Crystal Polymer Networks Doped with an Axially Chiral Fluorescent Dye: Circularly Polarized Luminescence and Anti‐Counterfeiting Applications

A modified dumbbell-shaped highly efficient broadband multifunctional polarizer for X and Ku band applications

Abstract A novel metasurface offering polarization conversion characteristic in five bands is studied and developed in this paper. To provide the anisotropic feature to the structure, a diagonally placed tapered rod is combined with two semicircular stubs. Due to the controlling ability to convert horizontal to vertical polarization and vice versa, and linear to circular polarization (CP), it serves as a multifunctional polarization converter. Simulation results suggest that the proposed polarizer functions as cross polarizer over 4.74−5.12 and 9.12−13.48 GHz. Additionally, it exhibits a distinct type of rotational sense across 4.24−4.68, 5.24−8.64, and 13.72–15.14 GHz in its linear to CP conversion behavior. The axial ratio of the polarizer is well below 3 dB throughout overall CP bands due to the minimum tolerance level in reflection phases with respect to acceptable limits. Moreover, it is noticed that the sense of CP is left-handed in the first band while right-handed in the remaining two bands. Thus, the suggested polarizer has potential to be integrated with antennas for satellite, defense, industry applications for getting the desired type of polarization in the distinguished bands.

Design and analysis of graphene-based PBG and EBG array antennas for wideband and multiband mm-wave applications

This paper presents a graphene-based PBG, EBG array antenna design with 40 × 40 mm2 dimensions for wide and multiband applications. The corporate CPW (Coplanar Waveguide) feeding technique is integrated with the ring, meander line, and periodic staircase with a slot pattern and augmented by conductive graphene for Electromagnetic Band Gap and Photonic Band Gap structures on the opposite side. This integration significantly enhances antenna performance, manifesting in superior radiation properties, increased gain, enhanced directivity, and resonating behavior with return loss of 16.4, 21.7, and 22.45 27.0, 25.3 dB in range of 24–25.25 GHz, 26.29–28.1 GHz, and 28.8–35.95 GHz and five bands with return loss of 26.1 , 21.1 , 22.2 , 31 , and 15.5 dB in range of 25.28–26.25, 28.1–29.4, 30.7–33.5, 34–35.5, 36.2–40.0 GHz that covers wideband and Multiband applications concerning PBG and EBG structures, respectively. Furthermore, the proposed antennae exhibit peak gains of 8 dBi at 26.53 GHz and 9 dBi at 32 GHz, corresponding 86.1% and 79.4% peak efficiencies and ensure robust circular polarization at resonating notches cover the mm-Wave 5G frequency bands n257, n258, n259, n260, and n261 for 5G applications, supporting ultra-fast data rates and low-latency communication with ground-based radio navigation applications.

Multiple Energy Transfer Modes From o‐Carborane Dyad Induced by Synergetic Conformational Regulations and Intense Circularly Polarized Luminescence in Self‐Assembly Aggregates

AbstractPhotothermal modulated excited conformations in traditional optoelectronic materials have been extensively investigated for the manipulation of emissive properties. However, photoinduced molecular synergetic conformational changes, which are promising for controlling intramolecular energy transfer modes through molecular orbital breaking, are never been explored. Herein, a novel o‐carborane dyad composed of carbazole units as electron donors and triazine derivatives as electron acceptors is demonstrated to achieve conformation‐dependent emissions and abundant emissions via synergetic conformational changes. Notably, the resulting dyad exhibited multiple conformational changes that induced emissions through different energy transfer modes involved “through space” and “through bond.” Exactly, the electron spin from singlet to triplet state took a flip accompanied by molecular orbitals from π–π molecular orbitals in the space charge transfer style to π and σ molecular orbitals in the bond charge transfer mode. The circularly polarized luminescence (CPL) properties are systematically investigated, exhibiting intense CPL with large glum values. These results provide novel perspectives for elucidating the complicated emission changes in aggregated states, as well as unique perspectives on the relationship between molecular conformations, energy transfer modes, and molecular orbital breaking.

Switchable phase modulation and multifunctional metasurface with vanadium dioxide layer

Abstract Metasurface, comprising subwavelength unit cells, offers a flexible modulation of the optical phase. However, traditional metasurfaces are typically engineered to function solely in one mode, limiting their efficiency and adaptability. In this study, we proposed a switchable metasurface consisting of gold bars deposited on polyimide and vanadium dioxide (VO2) layer. Upon the phase transition of VO2, this switchable metasurface exhibits functionality in both transmissive and reflective modes. Specifically, it efficiently converts left circularly polarized (LCP) light into right circularly polarized (RCP) light. For the dielectric (metallic) phases of VO2, the design behaves as metalens with a focal length of 1000 (906) μm at working frequency of 1.2 THz, respectively. Furthermore, the vortex phase can be effectively manipulated with topological number from 1 to 4 through the analysis of the electric field distribution. A directional emission from 12.9° to 42.2° is obtained in the reflective mode and Airy beam paths way can also be well regulated at 1.49 THz. The phase modulation is further achieved by varying the inter-mediums and its thickness. Finally, the sensing ability is explored with different covered solution. Consequently, this multifunctional and adaptable metasurface offers valuable insights for the development of reflectors, modulators, lenses and sensors.

Full-zone optical spin injection in AlxGa1−xAs alloys

Abstract Full-zone optical spin injection in Al x Ga1−x As alloys is investigated by analyzing the degree of circular polarization (DCP) of luminescence in a quantum well architecture. Aluminium content in AlGaAs barrier layers is varied to explore both the direct- and indirect-bandgap regimes. For all the samples, experimental data are compared with a 30-band k .p model addressing the band structure of the alloy and the optical spin injection over the entire Brillouin zone. We observe circularly polarized luminescence arising from the spin generation either around Γ or the L valley. We interpret the specific shape of the DCP within a framework accounting for smaller electron spin relaxation at the higher k points of the X valley of the AlGaAs barrier layer. Moreover, it is found that the presence of strain plays a vital role in governing the magnitude and shape of the DCP spectra for near band-edge excitation while exciting spin-polarized carriers in the direct-bandgap AlGaAs. We believe that these findings are important for the realization of AlGaAs-based spin-photonic devices aiming at possible applications in quantum technology.

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.

Control of the light polarization in ferromagnetic diode structures InGaAs/GaAs/δ-Mn

Electric-field influence on the polarization of the quantum well photoluminescence is studied in the diode structures InGaAs/GaAs/δ-Mn with narrow GaAs spacer dS = 2–5 nm at small magnetic field. Weakening of the circular polarization degree with increasing electric-field evidence about significant contribution of the stationary mechanism of the carriers’ polarization due to their exchange coupling with a nearby ferromagnetic δ-Mn-layer.

Terahertz switchable vortex beam generator based on vanadium dioxide reflective metasurface

Vortex beams exhibit significant potential for applications in diverse fields, such as optical communications, particle manipulation, and quantum information, due to the orbital angular momentum (OAM) they carry. While substantial progress has been made in the generation of vortex beams and the control of their wavefronts, further optimization is necessary to enhance the variability of OAM modes and the modulation of focusing. This study presents three tunable vortex beam generators based on vanadium dioxide metasurfaces. By leveraging the insulator-metal phase transition of vanadium dioxide (VO2), these metasurfaces can convert incident left-circularly polarized (LCP) light into a deflected vortex beam with adjustable OAM modes, a switchable focused vortex beam, or a focused vortex beam with tunable OAM modes in the terahertz band. Specifically, by varying the angle of the incident light, a vortex beam carrying variable topological charges can be deflected over a range from -34° to 90°. Vortex beams with a topological charge of 1 enable reversible switching between near-focus (0.85 mm) and far-focus (3.2 mm), demonstrating highly effective tunable focusing capabilities. Additionally, focused vortex generators with switchable topological charges are proposed. Focused vortex beams with a topological charge of -1 are generated in the insulating state, while a topological charge of -2 is observed in the metallic state. These vortex beam generators allow for different phase gradient distributions in the phase transition states, enabling diverse OAM and variable focuses. This research has potential applications in areas such as dynamic imaging and optical communications.

Reconfigurable dielectric resonator antenna and array with frequency and polarization flexibility

To implement frequency and polarization hybrid reconfiguration, a 4 × 4 array has been investigated. The radiation elements of the antenna array consist of cylindrical dielectric resonators, Wilkinson power divider, PIN diode, and dielectric substrate. The PIN diode controls the states of each branch in the Wilkinson power divider to achieve frequency and polarization reconfigurability. To verify the feasibility of the design, a fabricated sample of the proposed antenna array has been measured. The results demonstrate that the antenna array can be switched freely between its operating frequencies and polarizations. It operates within a bandwidth of 1.93 to 4.6 GHz for frequency reconfiguration, and three common polarization states—linear polarization, left-handed circular polarization, and right-handed circular polarization—can be continuously tuned from 2.96 to 3.39 GHz.

Efficient Computation of Overlap Reduction Functions for Pulsar Timing Arrays.

Pulsar timing arrays seek and study gravitational waves (GWs) through the angular two-point correlation function of timing residuals they induce in pulsars. The two-point correlation function induced by the standard transverse-traceless GWs is the famous Hellings-Downs curve, a function only of the angle between the two pulsars. Additional polarization modes (vector or scalar) that may arise in alternative-gravity theories have different angular correlation functions. Furthermore, anisotropy, linear, or circular polarization in the stochastic GW background gives rise to additional structure in the two-point correlation function that cannot be written simply in terms of the angular separation of the two pulsars. In this Letter, we provide a simple formula for the most general two-point correlation function-or overlap reduction function (ORF)-for a gravitational-wave background with an arbitrary polarization state, possibly containing anisotropies in its intensity and polarization (linear and/or circular). We provide specific expressions for the ORFs sourced by the general-relativistic transverse-traceless GW modes as well as vector (or spin-1) modes that may arise in alternative-gravity theories.

Magnetic diffusion in solar atmosphere produces measurable electric fields

The efficient release of magnetic energy in astrophysical plasmas, such as during solar flares, can in principle be achieved through magnetic diffusion, at a rate determined by the associated electric field. However, attempts at measuring electric fields in the solar atmosphere are scarce, and none exist for sites where the magnetic energy is presumably released. Here, we present observations of an energetic event using the National Science Foundation’s Daniel K. Inouye Solar Telescope, where we detect the polarization signature of electric fields associated with magnetic diffusion. We measure the linear and circular polarization across the hydrogen Hε Balmer line at 397 nm at the site of a brightening event in the solar chromosphere. Our spectro-polarimetric modeling demonstrates that the observed polarization signals can only be explained by the presence of electric fields, providing conclusive evidence of magnetic diffusion, and opening a new window for the quantitative study of this mechanism in space plasmas.

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.

A novel circularly polarized antenna array methodology for early identification of kidney tumors

Kidney cancer is a significant health concern worldwide, with early detection crucial for successful treatment outcomes. Recently, there has been an increasing focus on investigating affordable and non-intrusive methods for detecting cancer at its early stages. This proposed approach delves into the utilization of antenna arrays to identify kidney cancer. Specifically, antenna array with circular polarization has been crafted to identify tumors in the human kidney. This array design has been implemented using CST software, operating at 2.4 GHz. The antenna array having a dimension of 150 mm x 150 mm. The array consists of four-square patches each having a length of 30 mm and the spacing between the patches is preferred to be 20 mm for ensuring the mutual coupling. FR4 substrate is used with the relative permittivity 4.3 and 1.6 mm thickness. The axial ratio of the circularly polarized antenna is 0.9 dB at 2.4 GHz. The reflection coefficient S 11 = –30dB. The renal phantom in humans has been built with the kidney, adrenal gland, ureter, skin, fat, and muscle components to allow for precise simulation. Following that, four stages of cancer tumors were built employing all of the necessary qualities. For every stage of the cancer tumor, the reflection coefficient growth and resonance frequency shift are calculated. For the initial stages, the resonance frequency shift is very low. Consequently, the primary determinant of detection is the rise in S 11 . For 3rd and 4th stages of the tumor, there is a significant change in resonance frequency and increase S 11 , which facilitates identification. The calculated specific absorption rate (SAR) is a smaller amount than the safety thresholds, indicating that using this method is safe. Overall, this research points to a novel, easy-to-use method for kidney cancer screening. This method has the following benefits: it is non-invasive, safe, quick, affordable, and comfortable, and it emits no ionizing radiation during the measurement process. Furthermore, a range of output parameters such as gain, directivity, and polar radiation have been accurately computed.