Hongya Chen

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.

High-efficiency spoof plasmon polariton coupler mediated by gradient metasurfaces

Gradient metasurfaces (GMs) can provide pre-defined wave vectors that are along the surface of GMs. When the additional wave vector is greater than that of incident waves, the incident waves can be coupled efficiently as spoof plasmon polaritons (SPPs) even under normal incidence. In this Letter, the design of SPP couplers was proposed based on GMs. A high-efficiency SPP coupler was designed using split-ring resonators. Both the simulation and experiment show that the GM can achieve nearly perfect SPP-coupling under normal incidence at the designed frequency.

Wideband radar cross section reduction using two-dimensional phase gradient metasurfaces

Phase gradient metasurface (PGMs) are artificial surfaces that can provide pre-defined in-plane wave-vectors to manipulate the directions of refracted/reflected waves. In this Letter, we propose to achieve wideband radar cross section (RCS) reduction using two-dimensional (2D) PGMs. A 2D PGM was designed using a square combination of 49 split-ring sub-unit cells. The PGM can provide additional wave-vectors along the two in-plane directions simultaneously, leading to either surface wave conversion, deflected reflection, or diffuse reflection. Both the simulation and experiment results verified the wide-band, polarization-independent, high-efficiency RCS reduction induced by the 2D PGM.

A Miniaturized Dual-Band FSS With Stable Resonance Frequencies of 2.4 GHz/5 GHz for WLAN Applications

In this letter, we propose an anchor-shaped loop unit-cell structure for compact frequency selective surfaces (FSSs) with dual-bandstop behavior in two wireless local area network (WLAN) frequencies 2.4 and 5.0 GHz. The proposed FSS possesses 230- and 300-MHz bandwidths with insertion loss less than -20 dB around the two central operating frequencies 2.4 and 5.0 GHz, respectively. In addition, the FSS exhibits excellent miniaturization with 0.065 λ × 0.076 λ unit cells, where λ represents the free-space wavelength. Furthermore, the unit-cell structure provides a stable performance for both TE- and TM- polarizations under incident angles 0°-60°. A prototype of the proposed FSS is fabricated and measured. Good agreement between the simulated and measured results is obtained.

Achieving wideband polarization-independent anomalous reflection for linearly polarized waves with dispersionless phase gradient metasurfaces

In this letter, we proposed to achieve wideband polarization-independent anomalous reflection for linearly polarized (LP) waves based on the phase gradient metasurface (PGM) with a dispersionless phase gradient. A polarization-keeping metasurface reflector for circularly polarized (CP) waves was firstly presented. Based on the reflector, a reflective PGM was designed to realize dispersionless but adverse phase gradients for left- and right-handed circularly polarized (LCP and RCP, respectively) waves. Under normal incidence, high-efficiency anomalous reflection occurs for both LCP and RCP waves with opposite-signed reflection angles. Under the LP wave incidence, the reflected waves are separated into two beams due to the decomposition of LP waves into LCP and RCP waves. The anomalous reflection of LP waves is independent of the polarization angle. Both the experimental and simulated results are consistent with theoretical predictions, which convincingly verifies the wideband polarization-independent anomalous reflection of LP waves.

Wideband selective polarization conversion mediated by three-dimensional metamaterials

In this paper, we proposed to use ultra-thin 3D metamaterials to manipulate the polarization of the transmitted electromagnetic waves. As an example, we designed a 3D metamaterial to serve as an ultra-thin linear-polarization converter, which overcomes the defects of bulky volume and narrow bandwidth of conventional polarization converters. Polarization selectivity and polarization convertibility are achieved simultaneously in the single-layer metamaterial. The physical mechanism is analyzed using reflection matrix and transmission matrix in details. Simulated cross-polarization and co-polarization conversions for TE and TM incident waves verify the polarization selectivity and polarization convertibility.

Wideband, wide-angle coding phase gradient metasurfaces based on Pancharatnam-Berry phase

A new concept of the coding phase gradient metasurface (CPGM) is proposed, which is constructed using the phase gradient metasurface as the coding elements. Different from the previous coding metasurface (CM), both the coding sequences and gradient phases in the coding elements are designed to manipulate the electromagnetic (EM) wave for the CPGMs, and thus the manipulation will be more flexible. As an example, wide-band, wide-angle CPGMs with zero and non-zero phase gradient based on Pancharatnam-Berry (PB) phase are achieved using the co-polarization reflection unit cells under circularly polarized (CP) wave incidence. Both theoretically calculated and numerically simulated scattering patterns of the designed CPGMs demonstrate the expected manipulations. Additionally, two kinds of random CPGMs with different phase gradients are designed for radar cross section (RCS) reduction, and the measured RCS reveals a good accordance with the simulation.

Broadband planar achromatic anomalous reflector based on dispersion engineering of spoof surface plasmon polariton

Planar reflectors are generally composed of non-uniform inclusions positioned on conducting sheet. Restricted by strong dispersion of the inclusions, the reflection of planar reflectors is usually chromatic. In this letter, we first obtain the dispersion relation for planar achromatic anomalous reflector (PAAR). Then, we propose to realize the dispersion relation based on dispersion engineering of spoof surface plasmon polariton (SSPP). Metallic blades structure is proposed to achieve the linear dispersion response by tailoring the weak dispersion region of SSPP. 6 metallic blade structures are designed to compose the super cell of the PAAR. A prototype was fabricated and measured. Both the simulation and experiment results show that the PAAR can achieve an achromatic reflected angle of 49.3° in 10.7–11.7 GHz under normal incidence.

Design of Super-Thin Cloaks With Arbitrary Shapes using Interconnected Patches

We proposed to design super-thin cloaks with arbitrary shapes using interconnected patches. The general design method of super-thin cloaks using interconnected patches is firstly demonstrated by presenting a square prism cloak. Then, the method is applied to cloak design of irregularly-shaped cloaks for two typical airfoils. By comparing the transmission amplitudes/phases, field distributions, bi-static scatterings with and without the cloak, the cloaking effects are demonstrated convincingly. Due to low profile and easy implementation, the design method can be readily extended to designing other practical cloaks with complicated shapes.

Ultra-wideband polarization conversion metasurfaces

We propose a ultra-wideband polarization conversion metasurface composed of copper sheet-backed asymmetric V-shaped resonators. The ultra-wideband polarization convertibility is resulted from multiple resonances of the V-shaped resonators. The simulation results show that the polarization conversion ratio (PCR) is nearly 100% for both x-and y-polarized normally incident EM waves at the four resonance frequencies and a 1:3 3dB bandwidth can be achieved for both normally incident x- and y-polarized waves. The metasurface possesses the merit of ultra-wideband and thus has great application values in novel polarization-control devices.