Broadband multifunctional scattering control based on novel reconfigurable polarization conversion metasurface

Reconfigurable metasurfaces (RMSs) that enable the switching function of absorption and polarization conversion have attracted increasing attention. However, the design of RMSs to achieve wideband and high efficiency for both absorption and polarization conversion functions simultaneously remains a great challenge. Here, we propose the design of a RMS structure with a high-efficiency cross-polarization conversion and nearly perfect absorption. The reconfiguration between different functions of polarization conversion and absorption is obtained based on the reversible insulator-to-metal phase transition of Vanadium dioxide (VO_{2}). When the VO_{2} is in insulator state, the RMS realizes the cross-polarization conversion function in the wideband of 1.04–3.75 THz with a relative bandwidth up to 113 % due to the multi-resonant modes of electric and magnetic resonances. Meanwhile, the nearly-perfect absorption is achieved in the range of 1.36–3.38 THz with the corresponding relative bandwidth up to 85 % for the VO_{2} in metallic state. Specially, the wideband and high-efficiency performance of these functionalities is maintained for a wide angle incidence. The capability of bi-functional switch and integration with polarization conversion and absorption in a single metasurface structure endowed with both wideband and high-efficiency characteristics for a wide incident angle is very promising for emerging RMS devices in the terahertz region.

Dynamic control transmission and polarization properties of electromagnetic (EM) wave propagation is investigated using chemical reconfigurable all-dielectric metasurface. The metasurface is composed of cross-shaped periodical teflon tubes and inner filled chemical systems (i.e., mixtures and chemical reaction) in aqueous solution. By tuning the complex permittivity of chemical systems, the reconfigurable metasurface can be easily achieved. The transmission properties of different incident polarized waves (i.e., linear and circular polarization) were simulated and experimentally measured for static ethanol solution as volume ratio changed. Both results indicated this metasurface can serve as either tunable FSS (Frequency Selective Surface) or tunable linear-to-circular/cross Polarization Converter at required frequency range. Based on the reconfigurable laws obtained from static solutions, we developed a dynamic dielectric system and researched a typical chemical reaction with time-varying permittivity filled in the tubes experimentally. It provides new ways for realizing automatic reconfiguration of metasurface by chemical reaction system with given variation laws of permittivity.

Polarization conversion and beam scanning metasurfaces are commonly used to reduce polarization mismatch and direct electromagnetic waves in a specific direction to improve the strength of a wireless signal. However, identifying suitable active and mechanically reconfigurable metasurfaces for polarization conversion and beam scanning is a considerable challenge, and the reported metasurfaces have narrow scanning ranges, are expensive, and cannot be independently controlled. In this paper, we propose a reconfigurable transmissive metasurface combined with a scissor and rotation actuator for independently controlling beam scanning and polarization conversion functions. The metasurface is constructed with rotatable unit cells (UCs) that can switch the polarization state between right-handed (RHCP) and left-handed circular polarization (LHCP) by flipping the UCs to reverse their phase variation. Moreover, independent beam scanning is achieved using the scissor actuator to linearly change the distance between the UCs. Numerical and experimental results confirm that the proposed metasurface can perform beam scanning in the range of 28° for both the positive and negative regions of a radiation pattern (RHCP and LHCP beams) at an operational frequency of 10.5 GHz.

Integrating tunable characteristics and multiple functions into a single metasurface attracts more and more attention. Herein, a reconfigurable bifunctional metasurface is proposed to realize the switch between broadband polarization conversion and absorption. The switchable performance can be achieved by changing the conductivity of phase‐change material Ge2Sb2Te5 (GST) in the way of heating. When the conductivity σ of GST is set to 0 Sm−1, the metasurface is a polarizer that can transform the x‐polarized wave into the y‐polarized wave in the range of 0.53–1.22 THz. Moreover, its polarization–conversion ratio (PCR) is more than 90% from 0.60 to 1.15 THz. As σ increases to 1 × 105 Sm−1, the metasurface absorbs more than 75% of the incident wave from 0.44 to 1.34 THz, which means it is a broadband absorber. In addition, the performance of the metasurface is verified by simulation, experiment, and theory. Through comparison, the three results have a high fitting degree. The reconfigurable metasurface provides a new way to develop switchable photonic devices in the terahertz frequency region.

In this paper, a polarization re-configurable meta-surface is proposed and verified. It is composed of split-ring-resonators (SRRs) including a pair of splits in each SRR and re-configurability is achieved using PIN diodes. It is printed on an FR4 dielectric substrate supported by a metallic ground plane in its backside. The ON/OFF combinations of four PIN diodes connected between the splits result in polarization re-configurability. The proposed meta-surface produces polarization conversion for the reflected wave when all four PIN diodes are in the OFF state. But, when the PIN diodes are in the ON state, there will be no polarization conversion for the reflected wave. The performance of this proposed meta-surface is very simple to implement and is designed in the frequency range 5.71- 10.72 GHz. Also, a study of polarization conversion for different angles of incidence are conducted and an almost stable performance is observed.

Polarization is one of the basic characteristics of electromagnetic (EM) waves, and its flexible control is very important in many practical applications. At present, most of the multifunction polarization metasurfaces are electrically tunable based on PIN and varactor diodes, which are easy to operate and have strong real-time performance. However, there are still some problems in them, such as few degrees of freedom of planar structure control, complex circuit, bulky sample, and high cost. In view of these shortcomings, this paper proposes a Miura origami based reconfigurable polarization conversion metasurface for multifunctional control of EM waves. The interaction between the electric dipoles is changed by adjusting the folding angle θ, thereby tuning the operating frequency of the polarization conversion and the polarization state of the reflected wave. This mechanical control method brings more degrees of freedom to manipulate EM waves. And the processed sample is with lightweight and low cost. To verify the performance of the proposed origami polarization converter, a Miura origami structure loaded with metal split rings is designed and fabricated. The operating frequency of the structure can be tuned in different folding states. In addition, by controlling the folding angle θ, linear-to-linear and linear-to-circular polarization converters can be realized at different folding states. The proposed Miura origami polarization conversion metasurface provides a new idea for reconfigurable linear polarization conversion and multifunctional devices.

High-performance devices with superior execution will facilitate the practical application of terahertz (THz) technology and foster THz innovation. In this paper, taking advantage of the phase transition characteristics of vanadium dioxide (V O 2), a reconfigurable metasurface with absorption and polarization conversion capacities is proposed. The metallic condition of V O 2 results in the formation of a wideband absorber. It provides more than 90% absorption over a broad spectral range from 3.32 to 5.30THz. Due to the regularity of the meta-atom, the absorber is not polarization-delicate and keeps a high retention rate in the scope of incoming angles from 0° to 45°. When V O 2 is in the insulating condition, the calculated outcomes demonstrate that the cross-polarization conversion rate can reach more than 90% in the range of 2.29-7.85THz when x-polarized or y-polarized waves are incident vertically. The proposed metasurface is likely to be used in the fields of emitters, sensors, imaging systems, and wireless communication.

Switchable bi-functional water-based metasurface for high efficiency and wideband polarization conversion and absorption

Polarization conversion metasurfaces are widely used in optical devices, microwave devices and communication systems, owing to their unique polarization modulation characteristics. However, in some applications (such as folded reflectarrays), the unit cell must be capable of polarization conversion and phase modulation. To the best of our knowledge, there are only a few related designs with both the functionalities. In this paper, we propose a well-performing 1-bit reconfigurable coding metasurface with polarization conversion. It realizes linear-to-linear polarization conversion in a 1.32 GHz bandwidth, and the conversion loss is within 1 dB. Simultaneously, the metasurface achieves a phase difference of approximately 180° by switching the working state of the PIN diodes. This metasurface has great potential for radar detection, folded reflectarrays, and other fields.

An ultrathin metasurface is made reconfigurable through the use of unit cells incorporating voltage-controlled varactor diodes. The phase characteristics of each unit cell are individually controlled for reconfigurability mechanisms. Two main applications are proposed in the domain of microwave devices and antennas. The planar metasurface is illuminated by a primary source and is firstly used as reconfigurable reflector allowing beam steering performances and frequency agility. A second functionality is also demonstrated, where the metasurface is used as a reconfigurable polarizer. Measurements are performed on a fabricated prototype to validate the concept.

With the rapid development of information and communication technology, intelligent wireless systems have a huge demand for devices with multi‐function integration and multi‐degree of freedom electromagnetic control. In this paper, a multifunctional folded transmitarray antenna (MFTA) using a reconfigurable metasurface is proposed to achieve simultaneous and independent modulation of beam and polarization. The beam scanning, arbitrary wave generator, and polarization conversion functions can be achieved only by adjusting the PIN diode bias on the reconfigurable metasurface. In order to prove the feasibility of the proposed method, a prototype is fabricated and verified by experiments. Both simulated and measured results verify the excellent performance of the MFTA. This work opens a door to multi‐functional integration and multi‐degree of freedom electromagnetic manipulate devices, which have great prospects in areas such as radar detection and wireless communication.

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.

The design of electromagnetic device with arbitrary polarization manipulation is the hot spot of the current research. Multifunctional reconfigurable electromagnetic devices have been put into wide applications in radar, satellite communication and other fields. In this work designed is a multifunctional reconfigurable polarization conversion metasurface based on two PIN diodes, which can realize linear polarization conversion, linear-circular polarization conversion and total reflection switching in the different frequency bands, and the multi-function converter can still maintain the high-efficient broadband conversion characteristics when the oblique incidence angle is less than 30 degrees. The polarization conversion and reconfigurability are mainly due to the anisotropy of the structure and the changes of coupling mode in different states of PIN diodes. In addition, the physical mechanism of polarization conversion is explained by surface current. The combined action of electric resonance and magnetic resonance results in polarization conversion. Finally, the experimental results of the sample are in good agreement with the simulation results. The device has the potential application values in polarization manipulation, frequency control, intelligent reflecting surface design, and antenna design and so on.

A reconfigurable metasurface with a switchable function, broad band, high efficiency, and ultra-compact size is crucial for the development of efficient and compact devices. We propose a bifunctional metasurface that utilizes vanadium dioxide (V O 2) and graphene to achieve high-efficiency absorption and polarization conversion (PC) in the terahertz (THz) range. In our design, an extra dielectric layer is added on the top of V O 2 and graphene. It is worth pointing out that the presence of the additional dielectric layer greatly enhances the coupling of the wave in the Fabry-Perot cavity, resulting in remarkable improvement in absorption and PC efficiency. Furthermore, by controlling the working state of V O 2 and graphene, the functionality of the metasurface can be flexibly switched among absorption, cross-polarized conversion, and linear-to-circular PC (LTC). Simulation results indicate that the metasurface works in the absorption mode when V O 2 is in a metal state, and it can efficiently absorb THz waves at 2.0-7.0THz with a remarkable relative bandwidth of 111.1%. Furthermore, the absorption is over 98.4% under a normal incident case and still maintains over 90% with an incident angle of 50° at 2.8-7.0THz. Importantly, by changing the conductivity of V O 2, the absorption can be flexibly adjusted, allowing for tuning the absorption between 10% and 98.4%. When V O 2 is in an insulator state, the function of the designed metasurface is altered to PC mode, and it can efficiently convert incident linearly polarized (LP) waves into cross-polarized waves with a PC ratio exceeding 95% at 1.8-3.4THz when the Fermi level of graphene is 1eV. When switched to the LTC mode, it can convert incident LP waves into right-circularly polarized waves with ellipticity less than -0.95 at 1.7-2.1THz and into left-circularly polarized waves with ellipticity greater than 0.90 at 2.7-3.0THz when the Fermi level of graphene is 0.55eV.

A reconfigurable polarization conversion meta-surface (PCM) is proposed, which can reflect the linear polarization (LP) wave into the orthogonal LP wave or LP wave with same polarization. In conversion mode, the proposed Re-PCM can operate over 4.5GHz∼5.5GHz maintaining the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\Gamma \text{xx}$</tex> less than - 15dB. In reflection mode, the proposed Re-PCM acts as a metal reflector.