Reflective Polarization Converter Research Articles

Realization of broadband reflective polarization converter using asymmetric cross-shaped resonator

Cross-shaped resonator (CSR) in metamaterial usually corresponds to adjust resonant characteristics. In this report, a simple and broadband reflective polarization converter is realized at GHz frequencies by breaking the symmetry of the CSR. The experimental results demonstrate that the polarization conversion ratio (PCR) over 0.8 is achieved from 8.3 GHz to 14.3 GHz for linearly polarized (LP) incident waves under normal incidence. The high polarization conversion efficiency can be sustained when the incident angle increases to 60 degrees. By taking advantage of surface current distribution and the interference theory, the physical mechanisms are elucidated in detail. Finally, the broadband polarization conversion can also be achieved by decreasing the geometrical parameters of the converter in the mid-infrared frequency range.

Design of reflective linear-circular polarization converter based on phase gradient metasurface

Manipulating the propagating direction and polarization state of electromagnetic wave is always fascinating and used in a wide field. One of the approaches to achieving this aim is typically based on steering the propagation phase of wave traveling inside an optical medium, such as dielectric lens. Nevertheless, this approach creates new problems, such as high loss, bulky volume and fabrication difficulty. Recently, metasurface was found to be a two-dimensional equivalence of metamaterial, which attracted a great deal of attention because of its unique properties and capability of manipulating and controlling electromagnetic waves on a sub-wavelength scale. So metasurface serves as an alternative approach to dealing with the loss and fabrication issues, and opens a door for bridging the gap between the fundamental research of the artificial structures and their device applications. A reflective phase gradient metasurface (PGM) achieving the linear-to-circular (LTC) polarization conversion and anomalous reflection simultaneously is designed in this paper. Firstly, the conventional cross-shaped structure is modified for enlarging the phase range. Then, six modified cross-shaped structures are designed cautiously to serve as quarter wave-plates, and achieve 60 phase difference between adjacent structures. The reflection phase difference between x-and y-direction components is 90, and their magnitudes are both equal to 0.5. Secondly, a one-dimensional PGM is constructed by distributing six modified cross-shaped quarter wave-plates one by one. Furthermore, an LTC polarization converter with an area of 216 mm216 mm is designed by placing 366 one-dimensional PGMs periodically. The mirror reflectivity and axial ratio are simulated and measured to verify the performances of LTC polarization conversion and anomalous reflection. The measured sample is fabricated by printing circuit board technique through using FR4 substrate, and a free space method is adopted in measurement in the anechoic chamber. In addition, the operating bandwidth can be evaluated from the reflective power density spectra. The measured results of mirror reflectivity, reflective power density spectra and axial ratio characteristic are in good agreement with the corresponding simulations, which shows that the mirror reflectivity is lower than -10 dB; the axial ration is lower than 2 dB within the frequency band of 13.8-14.7 GHz. Meanwhile, the theoretical reflection angles from the generalized Snell law are consistent with the CST microwave studio simulated results and measured results. Compared with the reported LTC polarization converters, the proposed LTC polarization converter not only achieves polarization conversion, but also can manipulate the output wave direction, thereby it has an important promising application value for microwave engineering and communication system.

Large-area, broadband and high-efficiency near-infrared linear polarization manipulating metasurface fabricated by orthogonal interference lithography

Manipulation of the polarization state using electromagnetic metasurface has attracted considerable attention in recent years. However, most previously demonstrated single-layer polarization conversion metasurfaces suffer from low polarization conversion efficiency, narrow operation bandwidth, or huge fabrication challenges, especially for the visible and near-infrared frequencies. In this letter, a broadband and high-efficiency reflective linear polarization converter composed of ellipse-shaped plasmonic planar resonator was demonstrated in the near-infrared region. A polarization conversion ratio in power larger than 91.1% is achieved from 730 nm to 1870 nm. Furthermore, orthogonal interference lithography is adopted to prepare the large-area optical polarization conversion metasurface. The fabrication strategy unplugs the bottleneck of the fabrication of the large-area metasurface in the optical regime, promising an unprecedented progress for optical communication and integrated optics.

Broadband and wide-angle reflective polarization converter based on metasurface at microwave frequencies

We propose to realize a broadband and wide-angle reflective polarization converter in microwave regions. The proposed converter can convert a linearly polarized (LP) wave to its cross-polarized wave at three resonant frequencies. It can also convert the LP wave to a circularly polarized wave at other two resonant frequencies. Furthermore, the proposed converter can achieve broad bandwidth with incident angle up to 45°. The simulated and measured results are in agreement in the entire frequency regions, and the bandwidth of polarization conversion over 75 % can be obtained from 7.6 to 15.5 GHz under normal incidence and from 7.8 to 13.0 GHz under incident angle of 45°. The surface current distributions of the proposed converter are discussed to analyze the physical mechanism. The converter tolerance to wide angle of incidence and the broad bandwidth could be useful in the range of applications in the microwave regions.

Multiple‐band reflective polarization converter based on complementary L‐shaped metamaterial

ABSTRACTIn this article, we numerically and experimentally investigate the electromagnetic responses of multiple‐band reflective polarization based on complementary L‐shaped metamaterial. The proposed reflective polarization converter can convert a linearly polarized wave to its cross‐polarized wave at the five resonant frequencies, which is also can convert the linearly polarized wave to circularly polarized wave at other six resonant frequencies. Furthermore, the incident circularly polarized wave can be transformed into the same rotational direction at five resonant frequencies after reflection, which is different from reflection by conventional materials. Simulations are in reasonable agreements with the experimental results in the entire frequency range, and the polarization conversion ratio is over 90% for both linear and circular polarizations in simulation. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:978–983, 2015

Multiple-band reflective polarization converter based on deformed F-shaped metamaterial

A three-layered deformed F-shaped metamaterial reflective polarization converter (RPC) is proposed to realize linear and circular polarization conversions. The proposed F-shaped RPC can convert a linearly polarized wave to its cross-polarized wave at the four resonant frequencies. It also can convert the linearly polarized wave to a circularly polarized wave at the other four resonant frequencies. In addition, the proposed F-shaped RPC can maintain the same rational direction at the five resonant frequencies when the incident is a circularly polarized wave and higher reflective coefficients can be obtained with the increase of the thickness of the dielectric layer. The simulated and measured results are in agreement in the entire frequency range, and the polarization conversion ratio is more than 85% for both linear and circular polarizations. Further simulations reveal that the polarization in the terahertz range can also be obtained by changing the thickness of the dielectric layer and the unit of the reflective polarization converter.

Multiple-band reflective polarization converter using U-shaped metamaterial

A multiple-band metamaterial reflective polarization converter (RPC) is proposed, which is composed of the dielectric substrate sandwiched with U-shaped metallic patterns and continuous metal film. The proposed U-shaped metamaterial RPC (UMM-RPC) can convert a linearly polarized wave to its cross polarized wave at the three resonant frequencies, which also can convert the linearly polarized wave to circularly polarized wave at other three resonant frequencies. Furthermore, the proposed UMM-RPC can maintain the same conversional direction at the three resonant frequencies when incident on a circularly polarized wave. The simulated and measured results are in agreement in the entire frequency range, and the polarization conversion ratio is over 90% for both linear and circular polarizations. The surface current distributions of the UMM-RPC are discussed to look into the physical mechanism. The proposed UMM-RPC has simple geometry but more operating frequency bands compared to the previous designs and can be used in applications such as antenna radome, remote sensors, and radiometer.

Reflective metamaterial polarization converter in a broad frequency range

We propose a broadband reflective metamaterial polarization converter which is composed of arrays of split-ring resonators (SRRs), a dielectric layer and a continuous metallic layer. For the case of a loss-free dielectric layer, the average transformation rate is around 90% at frequencies from 6.68 to 10.91 GHz, and the bandwidth is 56.66% of the central wavelength. The increased loss tangent of the dielectric layer is shown to induce a reduced transformation rate due to enhanced absorption.

A broadband wide‐incident‐angle reflective polarization converter

Abstract— A high‐performance reflective polarization converter which could be used in a backlight recycling system for liquid‐crystal‐display (LCD) devices is proposed. The device consists of a twisted‐nematic (TN) liquid‐crystal film, a uniaxial A‐plate, and a reflector. The configuration parameters, such as thickness and orientation of the films, are optimized using a genetic algorithm. As a result, the design can convert light from TM to TE polarization (or TE to TM) at a maximum 99.7%, minimum 91.3%, and average 96.7% conversion efficiency for the entire visible spectrum and incident angle from 0 to 60°. Such a broadband reflective polarization converter is particularly useful for enhancing the light efficiency and reducing the power consumption of LCDs.