Polarization Conversion Metasurface Research Articles

Ultra-wideband polarization conversion metasurface and its application cases for antenna radiation enhancement and scattering suppression

A double-layer complementary metasurface (MS) with ultra-wideband polarization conversion is presented. Then, we propose two application cases by applying the polarization conversion structures to aperture coupling patch antenna (ACPA). Due to the existence of air-filled gap of ACPA, air substrate and dielectric substrate are used to construct the double-layer MS. The polarization conversion bandwidth is broadened toward low-frequency range. Subsequently, two application cases of antenna are proposed and investigated. The simultaneous improvement of radiation and scattering performance of antenna is normally considered as a contradiction. Gratifyingly, the contradiction is addressed in these two application cases. According to different mechanism of scattering suppression (i.e., polarization conversion and phase cancellation), the polarization conversion structures are utilized to construct uniform and orthogonal arrangement configurations. And then, the configurations are integrated into ACPA and two different kinds of metasurface-based (MS-based) ACPA are formed. Radiation properties of the two MS-based ACPAs are improved by optimizing the uniform and orthogonal arrangement configurations. The measured results suggest that ultra-wideband polarization conversion properties of the MS are achieved and radiation enhancement and scattering suppression of the two MS-based ACPAs are obtained. These results demonstrate that we provide novel approach to design high-performance polarization conversion MS and MS-based devices.

Tunable Polarization Conversion and Rotation based on a Reconfigurable Metasurface

Polarization is an important property of electromagnetic (EM) wave and different polarization manipulations are required for varied optical applications. Here we report a reconfigurable metasurface which achieves both the polarization conversion and the polarization rotation in THz regime. The metasurface is reconfigured through the micro-electro-mechanical-systems (MEMS) actuation. The cross polarization transmittance from a linear polarized incidence is experimentally tuned from 0 to 28% at 2.66 THz. In addition, the polarization rotation angle is effectively changed from −12.8° to 13.1° at 1.78 THz. The tunable bi-functional metasurface for polarization conversion and the polarization rotation can be flexibly applied in various applications such as imaging, polarization microscopy and material analysis, etc.

A Circularly Polarized High-Gain Antenna With Low RCS Over a Wideband Using Chessboard Polarization Conversion Metasurfaces

A new approach for the gain enhancement and wideband radar cross section (RCS) reduction of an antenna based on the chessboard polarization conversion metasurfaces (CPCMs) is proposed. Compared with the previous low-RCS antennas, high gain and wideband low RCS of a circularly polarized (CP) antenna are achieved simultaneously. The proposed CPCM is the chessboard configuration of the polarization conversion metasurfaces (PCMs), which is made up of adjoining two-layer substrates with three metallic patterns. Low RCS is realized by 180° (±30°) reflection phase variations between two neighboring PCMs. Gain enhancement is achieved by employing a Fabry-Perot cavity, which is constructed by the PCM and the ground of the antenna. The antenna with CPCM operating at the $X$ -band, excited by a sequentially rotated feeding network, is fabricated and measured. Simulated and measured results show that the left-hand CP gain of the antenna with CPCM is at least 3 dB higher than that of the reference antenna from 8.5 to 9.5 GHz and the monostatic RCS is effectively reduced from 6 to 14 GHz.

High-efficiency polarization conversion phase gradient metasurface for wideband anomalous reflection

An ultra-wideband polarization conversion metasurface based on S-shaped metallic structure is designed and prepared. The simulation results show that the polarization conversion bandwidth is 14 GHz for linearly polarized normally incident electromagnetic waves and the cross-polarized reflectance is more than 99% in the range of 10.3 GHz–20.5 GHz. On the premise of high reflection efficiency, the reflective phase can be regulated by changing the geometrical parameter of the S-shaped metallic structure. A phase gradient metasurface composed of six periodically arrayed S-shaped unit cells is proposed and further demonstrated both numerically and experimentally. The specular cross-polarization reflection of the phase gradient metasurface is below −10 dB, which shows a good performance on manipulating the direction of the reflected electromagnetic waves.

A Low-RCS and High-Gain Circularly Polarized Antenna With a Low Profile

A low-radar-cross-section and high-gain broadband circularly polarized (CP) antenna with a low profile was specially designed using metasurface concepts. A polarization conversion metasurface is designed and used as the radiator of the proposed CP antenna. It is shown that a good axial ratio and high gain can be obtained over a broad band. Three kinds of artificial magnetic conductors are arranged around the polarization conversion metasurface. By making the discrepancies of the reflection phases among the artificial magnetic conductors and polarization conversion metasurface to be 90° in turn, the monostatic radar cross section of the proposed antenna is reduced in a wide frequency band covering the operation frequency band of the CP antenna. Good agreement between the experimental and simulation results is obtained.

Wideband RCS Reduction Using Polarization Conversion Metasurface and Partially Reflecting Surface

A high-gain antenna with wideband low radar cross-section (RCS) property using polarization conversion metasurface (PCM) and partially reflecting surface (PRS) is investigated. PCM and PRS are printed on two sides of a substrate, above the microstrip patch antenna to form Fabry–Perot (F-P) resonant cavity. Due to the symmetrical arrangement of PCM unit and its mirror unit, remarkable wideband radar cross-section reduction (RCSR) is obtained in both x - and y -polarizations. Simulated and measured results show that combination of PCM with PRS antenna contributes to significant in-band and out-of-band RCSR, as well as 7 dB gain enhancement. Wideband RCSR ranging from 9 to 20 GHz with maximum in -band value is 20 dB at 9.4 GHz, and 33 dB out of band verified its superiority in RCS control.

Polarization conversion of metasurface for the application of wide band low-profile circular polarization slot antenna

In this letter, based on a corner-cut square metasurface, a planar polarization conversion structure is presented and the application for wide band low-profile circular polarization (CP) slot antenna is proposed. The mechanisms for achieving the CP state from a linearly polarized incident wave and for broadening the working bandwidth of conventional slot antenna are analyzed theoretically. The wide band low-profile CP slot antenna is achieved with numerical optimizations and parameter studies. Both simulations and measurements are performed to demonstrate the proposed antenna, and good agreements are obtained. Such results will open the path for polarization conversion metasurfaces used in the CP antenna area.

Symmetry-based coding method and synthesis topology optimization design of ultra-wideband polarization conversion metasurfaces

In this letter, we propose the synthesis topology optimization method of designing ultra-wideband polarization conversion metasurface for linearly polarized waves. The general design principle of polarization conversion metasurfaces is derived theoretically. Symmetry-based coding, with shorter coding length and better optimization efficiency, is then proposed. As an example, a topological metasurface is demonstrated with an ultra-wideband polarization conversion property. The results of both simulations and experiments show that the metasurface can convert linearly polarized waves into cross-polarized waves in 8.0–30.0 GHz, obtaining the property of ultra-wideband polarization conversion based on metasurfaces, and hence validating the synthesis design method. The proposed method combines the merits of topology optimization and symmetry-based coding method, which provides an efficient tool for the design of high-performance polarization conversion metasurfaces.

Ultra-broadband and high-efficiency polarization conversion metasurface with multiple plasmon resonance modes**Project supported by the National Natural Science Foundation of China (Grant Nos. 61471292, 61331005, 61471388, 51277012, 41404095, and 61501365), the 111 Project, China (Grant No. B14040), the National Basic Research Program of China (Grant No. 2015CB654602), and the China Postdoctoral Science Foundation ( Grant No. 2015M580849).

In this paper, we present a novel metasurface design that achieves a high-efficiency ultra-broadband cross polarization conversion. The metasurface is composed of an array of unit resonators, each of which combines an H-shaped structure and two rectangular metallic patches. Different plasmon resonance modes are excited in unit resonators and allow the polarization states to be manipulated. The bandwidth of the cross polarization converter is 82% of the central frequency, covering the range from 15.7 GHz to 37.5 GHz. The conversion efficiency of the innovative new design is higher than 90%. At 14.43 GHz and 40.95 GHz, the linearly polarized incident wave is converted into a circularly polarized wave.

Ultra-wideband transparent 90° polarization conversion metasurfaces

We propose to realize ultra-wideband transparent 90° polarization conversion metasurfaces by combining multiple plasmon resonances and Fabry–Perot-like resonances. An ultra-wideband polarization conversion metasurface is designed using a double-head arrow structure and metal gratings. It has been demonstrated that the bandwidth can be broadened greatly based on multiple plasmon resonances, while the efficiency can be enhanced strongly based on Fabry–Perot-like resonances. The both simulated and measured results show that the bandwidth of cross-polarized transmission is very wide, with a 1:6 3 dB bandwidth. The experimental results agree well with simulation ones.

A circular polarization antenna designed based on the polarization conversion metasurface

A novel circular porlarization (CP) antenna is designed and fabricated by loading a kind of polarization conversion metasurface. The structure of polarization conversion metasurface is composed of metal slash and copper ground sheet, which is separated by an FR4 dielectric substrates with a thickness h=3 mm. When a normal electromagnetic wave incident on the whole surface vertically, the electric field of the wave can be decomposed into two components Evi and Evi. Under the excitation of the two components, resonance is induced between the metal slash and the copper ground sheet respectively, making their own reflection phase changed to = u - v = 180, eventually making the reflection wave appear with 90 polarization rotation. By taking the peculiarity of 90polarization rotation of the polarization conversion metasurface, we can modulate the linear polarization of microstrip slot antenna into the circular polarization radiation. Through adjusting the distance between the slot antenna and the polarization rotation metasurface, we can regulate the working frequency of the circular polarization. Simulated and experimental results show that the polarization conversion metasurface makes a high-efficiency polarization rotation at 8-12 GHz. And the center working frequency of the CP antenna is 9.1 GHz, the impedance bandwidth is 8.3-10 GHz. When the distance H = 4.5 mm between the microstrip slot antenna and the polarization conversion metasurface, the 3 dB axial ratio bandwidth is 8.3-8.8 GHz, the microstrip slot antenna may realize circular polarized radiation. When H = 20 mm, the 3 dB axial ratio bandwidth is 8.8-9.3 GHz, and the slot antenna can realize circular polarized radiation. When H = 8 mm, the 3 dB axial ratio bandwidth is 9.3-10 GHz, the slot antenna can realize circular polarized radiation. Experimental results are in agreement with the simulation results, showing the validity of this design method which may become a new approach for the CP antennain designing

Wideband RCS Reduction of a Slot Array Antenna Using Polarization Conversion Metasurfaces

A new approach to reducing the monostatic radar cross section (RCS) and preserving the radiation characteristics of a slot array antenna by employing polarization conversion metasurfaces (PCMs) is presented in this communication. The PCM is arranged in a chessboard configuration consisting of fishbone-shaped element. It is placed on the surface of the slot array antenna. The characteristics and mechanism of the RCS reduction are analyzed. Simulated and experimental results show that the monostatic RCS reduction band of the antenna with PCM ranges between 6.0 and 18.0 GHz for normally impinging both $x$ - and $y$ -polarized waves. The radiation characteristics of the antenna are well preserved simultaneously in terms of the impedance bandwidth, radiation patterns, and realized boresight gains.

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.

Achieving wide-band linear-to-circular polarization conversion using ultra-thin bi-layered metasurfaces

In this paper, we propose to achieve wideband linear-to-circular (LTC) polarization conversion by ultra-thin bi-layered metasurfaces. As an example, an LTC polarization conversion metasurface operating in 11.4–14.3 GHz is designed and fabricated, which is composed of two layers of metallic pattern arrays separated by a 1.5 mm-thick dielectric spacer. When linearly polarized waves impinge on the bi-layered metasurface, LTC polarization conversion transmission is greater than 90% over a wide frequency range from 11.0 GHz to 18.3 GHz. Meanwhile, the axis ratio is lower than 3 dB in 9.8–18.3 GHz. This wide-band and highly efficient LTC polarization conversion transmission is analyzed theoretically. The measured LTC polarization conversion transmissions are well consistent with the simulated results.

High-efficiency ultra-wideband polarization conversion metasurfaces based on split elliptical ring resonators

Polarization state of electromagnetic waves plays a significant role in the fields of signal transmission and sensitive measurements. High-efficiently manipulating and controlling polarization state by two-dimensional flat metamaterials over a wider bandwidth has been turned into hot issues in recent years. A polarization conversion metasurface based on the split elliptical ring resonator is designed, simulated, and experimentally validated in the microwave regime. The proposed metasurface can convert a linear polarization state into its orthogonal one with a high efficiency for an ultra-wide band. Theoretically, the mechanism of polarization conversion is explained by the theoretical models of high-impedance surface and multi-plasmonic resonances. The metasurface has a strong anisotropy, which behaves as a high-impedance surface, and serves as a metal sheet in orthogonal orientation in the vicinity of the resonant frequencies. The reflection phase has a delay of π for one of the two electric field components and remains unchanged for the other. As a result, the polarization angle of the synthesized reflection electric field rotates by π/2. The fourth-order plasmonic resonances are generated by the electric and magnetic resonances, which contribute to the bandwidth expansion of cross-polarization reflection. Numerically, by means of simulation and analysis on the axial ratio and flare angle of the split elliptical ring resonators, the influences of these structure parameters on the bandwidth and efficiency of the polarization conversion are clarified. And then the design method of multi-peaks and wideband polarization conversion metasurfaces with split elliptic ring resonators is proposed for different kinds of applications. Experimentally, the geometry is implemented within the currently available printing circuit techniques, and a free space method is adopted to measure the scattering coefficients. A polarization conversion ratio of the fabricated sample is larger than 85% at a relative bandwidth of 104.5%, and approximately 100% of the polarization conversion ratio can be achieved around the resonant frequencies. Experimental results are in good consistency with the simulation results. Compared with the anterior polarization conversion metasurfaces, the proposed metasurface broadens the cross-polarization bandwidth greatly with little efficiency expenses. These works provide beneficial guidance for manipulating and controlling polarization states of electromagnetic waves, and have potential applications in modern radar and communication systems, signal detection systems, and sensitivity measurement systems, etc.

Broadband perfect polarization conversion metasurfaces**Project supported by the National Natural Science Foundation of China (Grant Nos. 61331005, 11204378, 11274389, 11304393, and 61302023), the National Science Foundation for Post-doctoral Scientists of China (Grant Nos. 2013M532131 and 2013M532221), the Natural Science Foundation of Shaanxi Province, China (Grant No. 2013JM6005), and the Aviation Science Foundation of China (Grant Nos. 20132796018 and 20123196015).

We propose a broadband perfect polarization conversion metasurface composed of copper sheet-backed asymmetric double spilt ring resonator (DSRR). The broadband perfect polarization convertibility results from metallic ground and multiple plasmon resonances of the DSRR. Physics of plasmon resonances are governed by the electric and magnetic resonances. Both the simulation and measured results show that the polarization conversion ratio (PCR) is higher than 99% for both x- and y-polarized normally incident EM waves and the fractional bandwidth is about 34.5%. The metasurface possesses the merits of high PCR and broad bandwidth, and thus has great application values in novel polarization-control devices.

Ultra-wideband polarization conversion metasurfaces based on multiple plasmon resonances

We propose to realize ultra-wideband polarization conversion metasurfaces in microwave regime through multiple plasmon resonances. An ultra-wideband polarization conversion metasurface is designed using a double-head arrow structure and is further demonstrated both numerically and experimentally. Four plasmon resonances are generated by electric and magnetic resonances, which lead to bandwidth expansion of cross-polarization reflection. The simulated results show that the maximum conversion efficiency is nearly 100% at the four plasmon resonance frequencies and a 1:4 3 dB bandwidth can be achieved for both normally incident x- and y-polarized waves. Experimental results agree well with simulation ones.