Dual-band Polarization Research Articles

Dual-band polarization conversions and optical diode based on bilayer T-shaped metamaterial

In this work, we propose a dual-band optical diode based on a bilayer T-shaped metamaterial. This optical diode can conveniently convert the x-polarized wave to y-polarized one at about 106 THz and convert the y-polarized to x-polarized wave at around 163 THz when linearly polarized waves impinge on the sample under a forward normal incidence (+z direction). The dual-band polarization conversion ratios can reach up to 99.9 % and 99.6 % at 106 and 163 THz, respectively. In addition, the bi-layer metamaterial works as an optical diode located around the frequencies 106 and 163 THz, i.e. the x- and y-polarized plane waves can pass through the metamaterial in the forward direction, however, they are prevented from backward. The maximum asymmetric transmission parameters are 0.46 and 0.50. At last, both the ratios and bandwidth of dual-band cross-polarization conversion can be conveniently manipulated by the rotation angle θ. This proposed dual-band polarization conversions and optical diode may have promising applications in optical nano-devices, such as optical switches and polarization converters.

Dual-band linear polarization converter based on multi-mode metasurface

This paper proposes a dual-band linear polarization converter based on multi-mode metasurface. The converter consists of square-patch-resonator-based metasurface etched with cross-slot, which is beneficial to separate the degenerate modes of the patch resonator in the first band, as well as to generate additional resonant modes for the second conversion band. Different from the traditional method of using multiple resonators for dual-band polarization converters, the proposed one only utilizes one multi-mode resonator. Additionally, the two bands can be tuned relatively independently by appropriately changing the physical parameters of the resonator. To verify the design method, one sample is fabricated and measured. The proposed linear polarization converter works in the two frequency ranges of 3.16–3.52 GHz and 7.19–8.61 GHz with a polarization conversion rate (PCR) ≥ 90 %.

Ultra-Low-Profile Continuous Transverse Stub Array for SatCom Applications

Modern K-/Ka-band satellite communications have become increasingly demanding in recent years with regard to the performance of the terminal antenna used in the link. These terminals should be high gain and broadband, as well as guarantee polarization diversity over a large field of view. A low profile is also highly desired to integrate the antenna system into a variety of moving platforms, such as aircraft and trains. An ultra-low-profile continuous transverse stub array is proposed here to tackle these challenges. The antenna array is realized in printed circuit board technology by adopting a contactless transition between the stacked-up layers without resorting to blind or buried vias. The proposed antenna is wideband (impedance matched within the 19–31 GHz band, i.e., ~50%) and provides multibeam radiation for polar angles as far as ±22.5°. The peak value of the gain is 19.7 dBi, and the maximum radiation efficiency equals 50%. Furthermore, the antenna array is combined with a dual-band polarization converter. The latter provides orthogonal circular polarization (CP) in two non-adjacent bands. The overall antenna system performs right- and left-hand CPs within the SatCom downlink and uplink in the K-/Ka-band, respectively. For each polarization, the axial ratio is below 3 dB over 9.47% and 4.42% fractional bandwidths, respectively.

Polarization insensitive dual band metamaterial with absorptance for 5G sub-6 GHz applications

A couple ring enclosed circular geometric resonator (CRECGR) based dual-band polarization insensitive metamaterial (MM) with high effective medium ratio (EMR), and excellent absorptance is proposed in this study, which can be utilized as a sensor and absorber in the 5G sub-6 GHz frequency range. A circular geometry-based unique patch has been introduced in the proposed unit cell to achieve high polarization insensitive properties with excellent absorption for the 5G sub-6 GHz spectrum. The distinctive feature of this proposed CRECGR unit cell is its simple and unique structure with a high EMR of 11.13, polarization insensitive up to 180°, and epsilon negative (ENG) properties, including a negative refractive index and near-zero permeability for 5G sub-6 GHz applications. Furthermore, this designed unit cell yields excellent absorption properties with high quality factor. The designed MM unit cell is fabricated on low loss Rogers RT5880 printed media with an electrical dimension of 0.089λ × 0.089λ × 0.017λ. The performance of the designed CRECGR metamaterial is determined using Computer Simulation Technology (CST), Advanced Design Software (ADS), and measurements. The CRECGR unit cell offers dual resonances at 3.37 GHz and 5.8 GHz, covering the 5G sub-6 GHz band with ENG, near-zero permeability and negative index. The polarization insensitive properties of the unit cell were also investigated for maximum angle of incidence, which confirmed the identical response. The simulated outcome is verified by experiment with excellent accordance. Moreover, the unit cell performance with a complete backplane is explored, noting a maximum absorption of 99.9% for all normal and oblique incidence waves, suitable for sensing and antenna systems. In addition, the suggested unit cell sensing performance is evaluated using the permittivity-based sensing model. The proposed MM outperforms recent related studies in terms of polarization insensitivity up to 180°, high insensitive absorptivity, high EMR, and sensing applications. These features prove that the proposed CRECGR metamaterial is perfect for 5G Applications.

Transmissive type dual band polarization converter integrated microstrip patch antenna in THz regime

This article proposes the generation of both LHCP and RHCP waves simultaneously –at two distinct frequencies by using a single-layered compact polarization converter (PC). The proposed PC has been designed with a gold pattern inscribed on a polyimide substrate. A modified I-shaped structure with semi-circular curved ends provides a quadrature phase shift between the orthogonal components of the incident electric field with a high transmission coefficient and low insertion loss across the two THz frequency bands. Two equivalent circuit models have been proposed for TE and TM modes separately. As a proof of concept of the proper functioning of the proposed PC, one dual-band linearly polarized antenna is designed and integrated with the PC. The linearly polarized radiated waves from the dual-band antenna across 1.55 THz and 4.05 THz have been successfully converted into both the RHCP and LHCP waves simultaneously. The integration of a simple profile PC with a dual-band THz antenna to produce dual CP radiated waves simultaneously are the key achievements of this proposed work. Moreover, the results of equivalent circuit models for both TE and TM modes are justified after proper validation with the full-wave EM simulation results. The proposed dual-band PC, dual-band THz antenna, and the integrated structures are systematically investigated using FEM-based CST Microwave studio.

Dual-Band Polarization Conversions and Optical Diode Based on Bi-Layer T-Shaped Metamaterial

Dual-Band Polarization Conversions and Optical Diode Based on Bi-Layer T-Shaped Metamaterial

Fully Metallic Dual-Band Linear-to-Circular Polarizer for K/Ka-band

A dual-band polarizer is presented that converts linear polarization into circular polarization with orthogonal handedness in the satcom bands 19.7–20.2 GHz and 29.5–30 GHz. The polarizer consists of three identical cascaded perforated metallic screens, whose perforations are periodically repeated crosses of two sizes. Unlike previously reported dual-band polarizers, our design is fully metallic, which results in low losses and makes it suitable for space applications. A prototype of the polarizer with 20 × 20 unit cells is manufactured, and the measurement results agree well with the simulated results. In the nominal satcom bands, the measured axial ratio and the insertion loss are better than 1.7 and 0.67 dB. In the bands 18.9–20.3 GHz and 29.1–30.1 GHz, the measured axial ratio and insertion loss are below 3 and 1 dB.

A Dual-Band Polarization Insensitive Metamaterial Absorber with a Single Square Metallic Patch for Sensing Application

A Dual-Band Polarization Insensitive Metamaterial Absorber with a Single Square Metallic Patch for Sensing Application

High-Efficiency Polarizer Reflectarray Antennas for Data Transmission Links from a CubeSat

This paper presents two designs of high-efficiency polarizer reflectarray antennas able to generate a collimated beam in dual-circular polarization using a linearly polarized feed, with application to high-gain antennas for data transmission links from a Cubesat. First, an 18 cm × 18 cm polarizer reflectarray operating in the 17.2–22.7 GHz band has been designed, fabricated, and tested. The measurements of the prototype show an aperture efficiency of 52.7% for right-handed circular polarization (RHCP) and 57.3% for left-handed circular polarization (LHCP), both values higher than those previously reported in related works. Then, a dual-band polarizer reflectarray is presented for the first time, which operates in dual-CP in the frequency bands of 20 GHz and 30 GHz. The proposed antenna technology enables a reduction of the complexity and cost of the feed chain to operate in dual-CP, as a linear-to-circular polarizer is no longer required. This property, combined with the lightweight, flat profile and low fabrication cost of printed reflectarrays, makes the proposed antennas good candidates for Cubesat applications.

Terahertz dual-band polarization control and wavefront shaping over freestanding dielectric binary gratings with high efficiency

Metasurfaces for multi-band or wideband polarization control are usually achieved by cascading or nesting several elements in a period, which complicate the structure and introduce crosstalk. In this work, independent polarization control is achieved around two terahertz frequencies, 0.14 THz and 0.3 THz, through a simple binary one-dimensional grating. The correlation of the phase retardation with frequency is broken, since it is determined by the propagation of a single mode at the lower frequency and by the interference of two modes at the higher frequency. Four gratings capable of different types of dual-band polarization control, a half-half wave plate, a half-quarter wave plate, a quarter-half wave plate and a quarter-quarter wave plate, are designed and experimentally tested. All the samples are made of polymers and 3D-printed as freestanding lightweight structures. The experimental results of all the samples validate polarization conversion with state-of-the-art high efficiency. Simulation results indicate their favorable bandwidth of more than 30%. The half-half wave plate gratings are further applied to build a metalens for efficient dual-band beam focusing based on the geometric phase. They show great potential in developing multifunctional terahertz elements using simple configurations.

Additive Manufacturing of a Dual Band, Hybrid Substrate, and Dual Polarization Antenna

We describe the additive manufacturing results pertaining to a multi-function antenna aperture. The antenna consists of customized high dielectric and low loss feedstocks as the enabling technology. The 3D printed prototype shows agreement with simulation while providing excellent performance.

Reconfigurable linear polarization conversion based on spatial-order kirigami metasurfaces

With the development of intelligent technology, it is essential to develop polarization-conversion devices with adaptable electromagnetic (EM) performance for practical applications. Up to now, most of attempts have relied on PIN diodes and varactor diodes for electrical tuning, typically featuring simplicity and timelineness. However, the shortcomings are also notable, such as less degrees of freedom (DoFs), more complex circuits and more expensive. In view of this, here we propose a kind of spatial-order metasurface for reconfigurable polarization conversion based on kirigami concept. By adjusting the folding angle <i>β</i>, the interaction between neighboring dipoles can be progressively changed and thus the operation frequency of polarization conversion can be shifted. Such a mechanical reconfigurable strategy brings about more DoFs for tuning and is cheaper and extraordinary convenient in practice. To verify the feasibility of our concept, a proof-of-concept spatial-order kirigami metasurface is proposed for the dual-band reconfigurable linear polarization conversion based on asymmetric chiral split ring resonators (SRRs). Experimental results show that the linear polarization operates at 5 and 5.8 GHz when folding angle is <i>β</i> = 10°, these frequencies are shifted to 5.8 and 7.2 GHz when <i>β</i> = 45°: a tuning range is expanded by 18.5%. In addition, the Poisson’s ratio and relative density of proposed kirigami metasurface as a function of <i>β</i> are also theoretically analyzed. The results show that the Poisson’s ratio increases with the value of <i>β</i> increasing. The relative density can be reduced to 1.5% of its unfolded planar counterpart. Our spatial-order kirigami metasurface strategy paves the way for implementing the reconfigurable linear polarization conversion and multifunctional devices.

A metasurface design method for dual wide band radar cross section reduction

Metasurface has attracted much attentions due to its ability of flexible manipulation of electromagnetic wave. However, the metasurface is limited to the single operating band and poor design generality when it is used for radar cross section (RCS) reduction. In this paper, a stacked metasurface design method has been developed to flexibly achieve dual wide band RCS reduction. Two subarrays with polarization conversion characteristic are firstly designed to operate in two wide bands, respectively. Then a low-pass frequency selective surface (FSS) is developed and sandwiched between two metasurface subarrays to achieve a subarray with the dual-band polarization conversion performance. With the arrangement of the dual-band subarray into a 2×2 array in a rotation way according to the polarization cancellation, the resultant metasurface structure has two −10 dB RCS reduction bands covering 6.6-12.7 GHz and 27.8-38.1 GHz. The designed prototype is fabricated and measured. The simulation and measurement results are given to demonstrate the good dual-band RCS reduction performance.

Polarizer-free polarimetric image sensor through anisotropic two-dimensional GeSe

Light polarization could provide critical visual information (e.g., surface roughness, geometry, or orientation) of the imaged objects beyond prevailing signals of intensity and wavelength. The polarization imaging technology thus has a large potential in broad fields such as object detection. However, intricate polarization coding is often required in these fields, and the existing complicated lensed system and polarizers have limited the miniaturization capabilities of the integrated imaging sensor. In this study, we demonstrate the utilization of two-dimensional (2D) in-plane anisotropic α-GeSe semiconductor to realize the polarizer-free polarization-sensitive visible/near-infrared (VIS-NIR) photodetector/imager. As the key part of the sensor system, this prototype Au/GeSe/Au photodetector exhibits impressive performances in terms of high sensitivity, broad spectral response, and fast-speed operation (∼103 AW−1 400–1050 nm, and 22.7/49.5 µs). Further, this device demonstrates unique polarization sensitivity in the spectral range of 690–1050 nm and broadband absorption of light polarized preferentially in the γ-direction, as predicted by the analysis of optical transition behavior in α-GeSe. Then we have successfully incorporated the 2D GeSe device into an imaging system for the polarization imaging and captured the polarization information of the radiant target with a high contrast ratio of 3.45 at 808 nm (NIR band). This proposed imager reveals the ability to sense dual-band polarization signals in the scene without polarizers and paves the way for polarimetric imaging sensor arrays for advanced applications.

Design and experimental analysis of dual-band polarization converting metasurface for microwave applications

The manipulation of polarization state of electromagnetic waves is of great importance in many practical applications. In this paper, the reflection characteristics of a thin and dual-band metasurface are examined in the microwave frequency regime. The metasurface consists of a 22 × 22 element array of periodic unit cells. The geometry of the unit cell consists of three layers, including a 45° inclined dipole shape metal patch on top, which is backed by a 1.6 mm thick FR-4 substrate in the middle, and a fully reflective metallic mirror at the bottom. The proposed surface is exposed to horizontally (x) or vertically (y) polarized plane waves and the co and cross polarization reflection coefficients of the reflected waves are investigated experimentally in the 6–26 GHz frequency range. The metasurface is designed to convert incident waves of known polarization state (horizontal or vertical) to orthogonal polarization state (vertical and horizontal) in two distinct frequency bands, i.e. 7.1–8 GHz and 13.3–25.8 GHz. In these two frequency bands the simulated and experimental results are in good agreement. The polarization conversion ratio (PCR) of the surface is greater than 95% in the targeted frequency bands. A detailed parametric analysis of the metasurface is also discussed in this work and it has been estimated that the surface has the additional ability to convert linearly polarized waves to circularly polarized waves at several distinct frequencies. The proposed metasurface can be utilized in sensor applications, stealth technology, electromagnetic measurements, and antennas design.

Dual-band terahertz polarization converter with high-efficiency asymmetric transmission

We present a terahertz wave dual-band polarization converter with near-perfect asymmetric transmission (AT) performance based on anisotropic metamaterial that is composed of a bi-layered subwavelength metal grating sandwiched with symmetrical dual radar structure array. It can achieve high efficiency dual-band polarization conversion and high efficiency AT performance in terahertz region. The results show that the polarization conversion rate (PCR) of the terahertz wave exceeds 99% under the forward (-z)/backward (+z) direction incidence in two terahertz bands from 0.38 THz to 1.34 THz and from 1.40 THz to 2.23 THz with a relative bandwidth of 111.63% and 45.73% respectively. The corresponding AT performance in excess of 0.8 is from 0.60 THz to 1.12 THz and from 1.61 THz to 1.98 THz with a relative bandwidth of 60.47% and 20.61% respectively. Due to the excellent charming performance, the proposed structure has great application potential in terahertz isolator.

All-Metal 3-D Frequency-Selective Surface With Versatile Dual-Band Polarization Conversion

A dual-band periodic structure is here proposed, which allows for versatile frequency selectivity and polarization conversion functionality. The structure is a monolithic full-metal piece, and it is built from the arrangement of unit cells consisting of waveguide sections at cutoff loaded with compound perforations. The topology of such unit cells enables the efficient and independent interaction with vertical and horizontal electric field components illuminating the periodic structure. A circuit model is proposed to characterize the cells and understand their behavior. Three different examples of cells are designed to illustrate the structure versatile functionality. One of these examples is manufactured, consisting of a dual-band structure that converts linear polarization into circular with orthogonal senses of rotation at each band. The experimental results are in good agreement with the theoretical predictions, thus validating the underlying operation mechanism and its practical feasibility.

Dual-band dual-polarization reconfigurable THz antenna based on graphene

A dual-band polarization reconfigurable terahertz antenna is proposed by incorporating a monopole antenna with a graphene-based dual-band active polarization converter metasurface (APCM). The APCM unit cell adopts two perpendicular slots on the top and two biased graphene patches on the bottom, which can be switched from ON (polarization conversion) to OFF (polarization maintain) in dual-band by adjusting the chemical potentials of graphene from 0 to 0.5 eV. By loading the APCM array under the monopole antenna, the dual-band polarization reconfigurable THz antenna achieves four working states including dual linear polarizations and dual circular polarizations.

A SIW-Based Polarization Rotator With an Application to Linear-to-Circular Dual-Band Polarizers at $K-/Ka$ -Band

A polarization rotator based on substrate integrated waveguide (SIW) is proposed in this article. The rotator is designed as a dual-band, single-layer, frequency-selective surface (FSS) that transmits a wave rotated of 90° with respect to the incident one in one of the two bands maintaining unchanged the polarization in the other one. Other than the design and characterization of the rotator, its application to a linear-to-circular dual-band polarizer is also investigated. To this purpose, the rotator is coupled to a conventional meander line polarizer generating orthogonal circular polarizations (CP) in the two bands. This configuration is useful in SatCom applications where the required high isolation between TX and RX channels is obtained assigning orthogonal polarizations to the two bands. As a design example, a prototype is designed and experimentally validated in the SatCom K-/Ka -bands. Measured performance shows an isolation between the TX and RX channels of more than 35 dB and insertion losses which do not exceed 1.5 dB in the two operating bands.

Dual-band transmissive circular polarization generator with high angular stability.

Metasurfaces (MSs) offer us an efficient way to control electromagnetic wave polarization due to its capability of flexible wave manipulation and compact configurations. However, the design of dual-band polarization conversion MS with high angular stability is still a challenge, especially in transmission geometry. Here, we propose a dual-band linear-to-circular (LTC) polarization conversion MS with high angular stability by using an array of multi-resonance meta-atoms. The meta-atom consists of two outer double split-ring layers and a central bar layer with circle-slot and can realize circular polarization at two bands with high efficiency and angular stability. The MS can transform the x-polarized wave into right-hand circular polarization (RHCP) at lower band and left-hand circular polarization (LHCP) at higher band and an opposite role for the y-polarized wave. The results show that the MS operates with insertion loss less than 0.5 dB and 0.3 dB and axial ratio below 3 dB in the frequency range of 9.05-9.65 GHz and 12.55-13.1 GHz, respectively. Moreover, our MS is insensitive to the oblique incident waves and can operate at high performance with the incident angle less than 55°. The proposed MS provides a new avenue to design meta-devices with dual frequency property and also high angular stability.