Polarization Rotation Properties Research Articles

From Helices to Crystals: Multiscale Representation of Chirality in Double-Helix Structures.

Single crystals with chiral shapes aroused the interest of chemists due to their fascinating polarization rotation properties. Although the formation of large-scale spiral structures is considered to be a potential factor in chiral crystals, the precise mechanism behind their formation remains elusive. Herein, we present a rare phenomenon involving the multitransfer and expression of chirality at micro-, meso-, and macroscopic levels, starting from chiral carbon atoms and extending to the double-helical secondary structure, ultimately resulting in the chiral geometry of crystals. The assembly of the chiral double helices is facilitated by the dual characteristics of amide groups derived from amino acids, which serve as both hydrogen bond donors and receptors, similar to the assembly pattern observed in DNA. Crystal face analysis and theoretical morphology reveal two critical factors for the mechanism of the chiral crystal: inherent intrinsically symmetrical distribution of crystal faces and their acquired growth. Importantly, the magnetic circular dichroism (MCD) study reveals the strong magneto-optical response of the hypersensitive f-f transition in the UV-vis-NIR region, which is much stronger than previously observed signals. Remarkably, an external magnetic field can reverse the CD signal. This research highlights the potential of lanthanide-based chiral helical structures as promising magneto-optical materials.

Optical scheme of developing Hamming code-based error detection and correction using Toffoli gates with frequency encoded data

Bit-error detection and correction is a very important part of a data communication network. In this article, we propose an optical approach to designing an error detection and correction circuit using Hamming code-based frequency encoded binary data and Toffoli gates. Here, the Toffoli gates are made of semiconductor optical amplifiers (SOAs) that work based on the nonlinear polarization rotation property. The characteristics of SOA, including very fast switching action (about 0.01 ns), low power consumption, frequency independent cross-polarization gain in the C-band, cascading property, etc., make the scheme attractive. The frequency encoded data-based proposed scheme will be effective for WDM communication networks. MATLAB simulation results testify to the feasibility of the proposed scheme.

A band-pass frequency selective surface with polarization rotation

A band-pass frequency selective surface (FSS) with polarization rotation property is proposed. The proposed polarization rotating FSS (PR-FSS) is a two-dimensional periodic structure, its unit cell is an antenna-filter-antenna (AFA) module, and the polarization directions of the upper and lower antennas in each AFA module are orthogonal to each other, so the PR-FSS can achieve frequency selection and 90 degrees polarization rotation at the same time. The numerical simulation demonstrate that the anticipated frequency selection and polarization rotation are realized by the PR-FSS in the frequency band from 8.84 GHz to 10.30 GHz with a relative bandwidth of 15.26%, and the maximum insertion loss in the pass band is only 0.17 dB. Finally, one effective experiment validation is carried out, a reasonable agreement is observed between the experimental and simulated results except for a slight deviation caused by fabrication error and measurement tolerance.

Co- and Cross-Polarization Decoupling Structure With Polarization Rotation Property Between Linearly Polarized Dipole Antennas With Application to Decoupling of Circularly Polarized Antennas

A decoupling structure with polarization rotation (DSPR) property is proposed to reduce the mutual coupling between co- or cross-polarized antennas. The proposed DSPR generates a neutralization wave with two orthogonally polarized components that can be controlled to cancel the original mutual coupling. The DSPR is placed above the arrays with orthogonal and parallel dipole elements. After applying the DSPR, the mutual coupling at the center frequency of 3.5 GHz is reduced to −40 dB for both arrays, and the overall mutual coupling is better than −26 dB within the band of 3.3–3.7 GHz, and the reflection coefficients remain below −12 dB. The antennas maintain stable radiation patterns within the operation bandwidth with a 0.5 dB increase of the realized gain. Since the DSPR can effectively reduce both co- and cross-polarization coupling, the mutual coupling between circularly polarized antennas in a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1 \times 4$ </tex-math></inline-formula> array is reduced to below −35 dB thanks to the DSPR. Finally, a prototype of the antenna array with orthogonal dipole elements loaded with the DSPR is fabricated and measured. The measured results are in excellent agreement with the simulated ones, demonstrating the effectiveness of the proposed DSPR for isolation enhancement between cross-polarized antennas.

Analysis of magnetically biased graphene absorber using anisotropic HIE-FDTD method

ABSTRACTAn anisotropic hybrid implicit-explicit finite-difference time-domain scheme is developed to investigate the magnetically biased graphene absorber. The anisotropic conductivity of the graphene is incorporated into the scheme by using the auxiliary difference equations. Numerical examples show that the presented scheme has much higher simulation velocity than the conventional finite-difference time-domain scheme, because the time increment in proposed method is not confined by the fine meshes in graphene sheet. Besides, the results validate that, by controlling the biased magnetic field, the graphene exhibits tunable polarization rotation property at Terahertz spectra and can be used to design magnetically tunable Terahertz absorber effectively.

Linearly Polarized Converters for Reflected and Transmitted Waves Based on Double-Split Ring Resonator

We propose and demonstrate the linearly polarized converters for reflected and transmitted waves based on a double-split ring resonator (DSRR). For reflective polarization converter, the three-layered metamaterial structure can rotate the polarization state of incident linearly polarized wave into its orthogonal one. The calculated results indicate that the polarization conversion ratio of reflective polarization rotator can reach unity (99.99%) at the resonant frequency. For transmissive polarization rotator, we propose a multi-layered metamaterial structure at terahertz frequencies which exhibits the incident y-polarized wave can be thoroughly and perfectly converted to the x-polarized output wave over the entire frequency range. The numerical simulation and theoretical calculation indicate that polarization conversion ratio of the y-polarized wave can be higher than 99.98% at the frequency range from 0.42 to 1.59 THz. Additionally, we investigate the polarization rotation properties based on optical activity and ellipticity. Specifically, the proposed structure can achieve simultaneously a multi-band 90o polarization rotation angle and an extremely low dispersion (lower than 0.25o, absolute value). The physical mechanism of polarization conversion is also analyzed based on the electronic field distribution at the resonance frequency.

Chiral metamaterial design using optimized pixelated inclusions with genetic algorithm

Chiral metamaterials have been a research area for many researchers due to their polarization rotation properties on electromagnetic waves. However, most of the proposed chiral metamaterials are designed depending on experience or time-consuming inefficient simulations. A method is investigated for designing a chiral metamaterial with a strong and natural chirality admittance by optimizing a grid of metallic pixels through both sides of a dielectric sheet placed perpendicular to the incident wave by using a genetic algorithm (GA) technique based on finite element method solver. The effective medium parameters are obtained by using constitutive equations and S parameters. The proposed methodology is very efficient for designing a chiral metamaterial with the desired effective medium parameters. By using GA-based topology, it is proven that a chiral metamaterial can be designed and manufactured more easily and with a low cost.

One-way absorber for linearly polarized electromagnetic wave utilizing composite metamaterial.

This paper presents the proposal and practical design of a one-way absorber for selective linearly polarized electromagnetic (EM) wave. The EM wave polarization rotation property has been combined with polarization selective absorption utilizing a composite metamaterial slab. The energy of certain linearly polarized EM wave can be absorbed along one particular incident direction, but will be fully transmitted through the opposite direction. For the cross polarized wave, the direction dependent propagation properties are totally reversed. A prototype designed with a total slab thickness of only one-sixth of the operating wavelength is verified through both full-wave simulation and experimental measurement in the microwave regime. It achieves absorption efficiency over 83% along one direction, while transmission efficiency over 83% along the opposite direction for one particular linearly polarized wave. The proposed one-way absorber can be applied in EM devices achieving asymmetric transmission for linearly polarized wave or polarization control. The composite metamaterial that combines different functionalities into one design may provide more potential in metamaterial designs for various applications.

Novel Polarization Rotation Technique Based on an Artificial Magnetic Conductor and Its Application in a Low-Profile Circular Polarization Antenna

A novel polarization rotation technique based on an artificial magnetic conductor (AMC) structure is proposed. A new polarization rotating reflective surface (PRRS) is designed using a newly proposed AMC as the unit cell. The height of the so-constructed PRRS is only 0.04 λ 0 . Our theoretical analysis shows that the polarization rotation property of the new PRRS is due to an impedance imbalance which can be analyzed using an equivalent circuit model. In addition, two polarization rotation bands and a large polarization rotation bandwidth of 29.1% can be achieved by using the new PRRS. Moreover, the new PRRS is applied for the first time to design a low-profile dipole antenna for the generation of circular polarization radiation. Three polarization states are readily achieved. Both simulation and measurement results demonstrate good right-handed circular polarization with a broad axial ratio bandwidth and a large axial ratio beamwidth in both the xoz and yoz planes.

A Retrodirective Antenna Array With Polarization Rotation Property

A planar passive retrodirective antenna (RDA) array with polarization rotation property is proposed in this paper using the substrate integrated waveguide (SIW) technology, which can be used in monostatic radar applications. The proposed RDA array adopts planar bandwidth-enhanced SIW cavity-backed wide slot antennas as the radiation elements. The polarization rotation property can be achieved by using radiation elements in two different configurations. A W-band prototype RDA array with 16 radiation elements is designed and fabricated using the single-layer printed circuit board (PCB) process at 79 GHz for automotive short-range radar applications. The measurement setup for monostatic and bistatic radar cross section (RCS) responses as well as the calibration process are presented. The retrodirective property and the polarization rotation property are realized by the proposed RDA array. The simulated and measured results of monostatic and bistatic RCS responses are in good agreement, which can cover an incident angle of ±17 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> from bore-sight with its normalized monostatic RCS response dropped by about 3 dB.

Reflective Liquid Crystal Polarization Rotator with Ultraviolet-Polymerizable Liquid Crystal Retardation Film

We demonstrate a reflective liquid crystal (LC) polarization rotator with a UV-polymerizable LC retardation film inside an LC cell. The LC polarization rotator consists of two birefringence layers; one layer is a UV-polymerizable LC film that acts as a quarter-wave plate and the other is a nematic LC layer that acts as an electrically tunable retardation film. The polarization direction of the linearly polarized incident light is found to rotate in a sufficient angular range of 2π, depending on the retardation of the electrically tunable LC layer. Additionally, good polarization rotation properties are achieved for an arbitrary polarization direction of the incident light. The influence of the error of the retardation from the designed value on the polarization rotation properties is investigated in detail. The polarization rotation function is found to slightly deteriorate with an increase in the retardation error of the UV-polymerizable LC film, whereas the ellipticity of the output light is sensitively enhanced with an increase in the retardation error of the quarter-wavelength plate.

A Novel Reflective Surface With Polarization Rotation Characteristic

A reflective surface with polarization rotation property is proposed in this letter. The primary function of the surface is to reflect the linearly polarized incident wave with 90° polarization rotation. The fractional bandwidth reaches up to 9.5%, with copolarization reflection coefficient better than -10 dB at normal incidence. Stable frequency responses in the passband have been obtained with oblique incidence for TE polarization. The periodic element of the proposed surface consists of a dual-mode substrate integrated waveguide (SIW) cavity resonator with horizontal and vertical slots on the same side. A parametric study of its frequency responses has been done with full-wave simulation. To verify the design method, a prototype designed at 35 GHz is fabricated and measured. The measured results are in good agreement with the numerical simulations.

Cancellation of Polarization Rotation in an Offset Paraboloid by a Polarization Grid

The polarization rotation properties of the field radiated from a polarization grid have been found to be similar to those in the aperture of an offset parabolic antenna. This observation suggests broadband cancellation of the polarization rotation in a large offset reflector by the opposite prerotation of the incident feed radiation via a polarization grid. Reduction of cross polarization from −24 dB without the grid to −39 dB with the grid wires is predicted in a numerical example. A previously unexplained polarization rotation measured using an offset parabolic grid is shown to be in good agreement with calculation.