Polarization-independent Property Research Articles

Ultra-Thin Polarization Beam Splitter Using 2-D Transmissive Phase Gradient Metasurface

A new 2-D ultra-thin transmissive phase gradient metasurface (TPGM) with polarization-independent property is proposed based on the generalized Snell’s law of refraction. The super unit cell of the tri-layer TPGM consists of $6 \times 6$ suitably selected elements with $- {60}^\circ $ phase gradient at $x $ -direction and 60° phase gradient at $y $ -direction, respectively. The characterizations and working mechanisms of the TPGM are investigated in depth through theoretical calculation, comparative analysis, and eletromagnetic (EM) simulation. Four types of TPGMs with different functionalities are proposed based on the derived four-step design method. Numerical results show that the TPGMs are capable of manipulating the differently polarized wave independently. For demonstration and potential applications, an ultra-thin polarization beam splitter (PBS) working at X-band is implemented by a specially designed 2-D TPGM and is launched by a wideband horn antenna from the perspective of high integration, simple structure, and low cost. Numerical and experimental results coincide well, indicating that the PBS advances in many aspects such as separating and controlling the orthogonally polarized waves with a polarized splitting ratio better than 18 dB, obtaining a comparable bandwidth of more than 600 MHz, gaining a high transmission efficiency and also adopting a simple fabrication process based on the convenient print circuit board (PCB) technology.

Phase interpretation of wideband splitting for TE polarization by embedded microstructure

The beam splitting control is proposed by an embedded two-layer grating. With the optimized grating parameters for the special duty cycle of 0.65, the novel grating can diffract both TE and TM polarizations into two orders with the 50/50 splitting ratio, where the polarization-independent property is exhibited. Most importantly, the wide bandwidth for the incident wavelength is achieved for TE polarization compared with the reported total internal reflection grating and the surface-relief single-layer grating. The physical essence of the wideband is well explained by the accumulated phase difference based on modal method. Since it is not easy to obtain the wide incident wavelength range for the conventional multilayer coatings and the surface-relief single-layer grating, the physical mechanism can offer an effective guideline to design grating-based beam splitter with the wide bandwidth for the incident wavelength.

An extremely wideband and lightweight metamaterial absorber.

This paper presents a three-dimensional microwave metamaterial absorber based on the stand-up resistive film patch array. The absorber has wideband absorption, lightweight, and polarization-independent properties. Our design comes from the array of unidirectional stand-up resistive film patches backed by a metallic plane, which can excite multiple standing wave modes. By rolling the resistive film patches as a square enclosure, we obtain the polarization-independent property. Due to the multiple standing wave modes, the most incident energy is dissipated by the resistive film patches, and thus, the ultra-wideband absorption can be achieved by overlapping all the absorption modes at different frequencies. Both the simulated and experimental results show that the absorber possesses a fractional bandwidth of 148.2% with the absorption above 90% in the frequency range from 3.9 to 26.2 GHz. Moreover, the proposed absorber is extremely lightweight. The areal density of the fabricated sample is about 0.062 g/cm2, which is approximately equivalent to that of eight stacked standard A4 office papers. It is expected that our proposed absorber may find potential applications such as electromagnetic interference and stealth technologies.

Performance investigation of incident bandwidth based on reflective two-layer grating with high efficiency

A novel reflective two-layer grating is proposed to obtain broad incident wavelength and angular bandwidths with the polarization-independent property. Although the conventional reflective single-layer grating can diffract high efficiency into the—1st order based on the mixed metal dielectric structure, deviations of the incident wavelength and angle will introduce much influence on the efficiency. By the reflective two-layer grating, the incident bandwidth can be improved greatly with high efficiency. The reflective two-layer grating can diffract efficiencies more than 90% into the—1st order within the incident wavelength range of 1376–1675 nm or the incident angular bandwidth of 33.05–51.21°. The presented reflective two-layer grating can have advantages of high efficiency and improved bandwidths. The given quite moderate fabrication tolerance should be significant for practical applications of such a reflective two-layer grating. • A reflective two-layer grating is presented for both TE and TM polarizations. • Incident bandwidths are improved greatly compared with the single-layer grating. • Moderate fabrication tolerance can make it significant for practical applications.

Two-Layer Dielectric Grating as Two-Port Beam Splitter

A two-port beam splitter is presented to obtain the 50/50 output based on the two-layer grating. The previously reported beam splitter grating can work only at the special prescribed incident angle. The deviation of incident angle introduces the effect on the splitting ratio uniformity. The proposed two-layer beam splitter grating is aimed to obtain the broad incident angular bandwidth. To optimize the beam splitter, a simplified modal method and rigorous coupled-wave analysis are employed to analyze the propagation process and to calculate the efficiency. Based on the optimized grating parameters, the 50/50 output can be obtained with the polarization-independent property. Most importantly, good splitting ratio uniformity can be exhibited within the broad angular bandwidth for both TE and TM polarizations. The polarization-independent property and the broad incident angular bandwidth are significant for practical applications.

Shape-dependent absorption characteristics of three-layered metamaterial absorbers at near-infrared

We experimentally demonstrate the absorption properties of designed metamaterial absorbers in the near-infrared wavelength regime. For the rectangular-shaped case, we demonstrate its polarization dependent absorbance at various incident angles. For each polarization, the absorbance is insensitive to the incident angle (up to 60°) and a maximum absorbance of 0.95 is obtained. Of particular interest we experimentally observe an absorption peak corresponding to a high-order resonance at 60° with an absorbance of 0.68 excited by the TM polarization. For the square-shaped case, we show its polarization-independent absorption property. A maximum absorbance around 0.65 is achieved at normal incidence and it remains high for incidence angles up to 50°.