Tuning the dispersion of effective surface plasmon polaritons with multilayer systems.

Recently, effective surface plasmon polaritons (ESPPs) induced by structural dispersion in bounded waveguides were theoretically demonstrated and experimentally verified. Despite the theoretical and experimental efforts, whether ESPPs can mimic real SPPs in every aspect still remains an open question. In this work, we go one step further to study the hybridization of ESPPs in multilayer systems. We consider transverse electric (TE) modes in a conventional rectangular waveguide and a parallel-plate waveguide (PPW) and derive analytically the dispersion relations and asymptotic frequencies of the corresponding ESPPs modes in sandwiched structures consisting of alternating dielectrics of different permittivities. Our results show that the ESPPs can be categorized into odd and even parities (owing to the 'plasmon' hybridization) in a similar way as natural SPPs supported by the insulator/metal/insulator (IMI) and metal/insulator/metal (MIM) heterostructures in the optical regime. The similarities and differences between ESSPs and their optical counterparts are also discussed in details, which may provide valuable guidance for future application of ESPPs at the microwave and terahertz frequencies.

Metasurfaced Reverberation Chamber.

The concept of metasurfaced reverberation chamber (RC) is introduced in this paper. It is shown that by coating the chamber wall with a rotating 1-bit random coding metasurface, it is possible to enlarge the test zone of the RC while maintaining the field uniformity as good as that in a traditional RC with mechanical stirrers. A 1-bit random coding diffusion metasurface is designed to obtain all-direction backscattering under normal incidence. Three specific cases are studied for comparisons, including a (traditional) mechanical stirrer RC, a mechanical stirrer RC with a fixed diffusion metasurface, and a RC with a rotating diffusion metasurface. Simulation results show that the compact rotating diffusion metasurface can act as a stirrer with good stirring efficiency. By using such rotating diffusion metasurface, the test region of the RC can be greatly extended.

Three-Dimensional Ordered Macroporous FePO4 as High-Efficiency Catalyst for Rechargeable Li-O2 Batteries.

The Li-O2 battery is receiving much recent attention because of its superhigh theoretical energy density. However, its performance is limited by the irreversible formation/decomposition of Li2O2 on the cathode and the undesired electrolyte decomposition. In this work, low-cost three-dimensional ordered macroporous (3DOM) FePO4 is synthesized by using polystyrene (PS) spheres template in a facile experimental condition and applied as a high-efficiency catalyst for rechargeable Li-O2 batteries, including good rate performance, high specific capacity, and perfect cycling stability. The superior performances can be attributed to the unique structure of 3DOM FePO4 cathodes, which can provide an efficient buffer space for O2/Li2O2 conversion. In addition, it is demonstrated that the Li+ intercalation/deintercalation behavior of 3DOM FePO4 in ether-based electrolyte can contribute to capacity for Li-O2 batteries over cycling. As a result, when there is no O2 in the environment, the Li-O2 cell can also be operated as a rechargeable Li-FePO4 cell with a perfect cycle capability.

Coplanar waveguide wideband band-stop filter based on localized spoof surface plasmons.

In this work, a wideband band-stop plasmonic filter based on localized spoof surface plasmons is reported, which consists of a coplanar waveguide (CPW) and an ultra-thin periodic corrugated metallic strip with defect units at the back of the substrate. Defect units are used to localize the transmission energy along the CPW. Each defect unit can introduce a narrow stop band, and a series of defect units is judiciously designed to form a broadband CPW band-stop filter. The center frequency and bandwidth of the filter can be tuned by the heights and numbers of the defect units. In addition, a T-shaped unit is designed to increase the equivalent height of the lateral branch so as to realize the miniaturization of the vertical geometric dimension. Theoretical analysis of the filter has been conducted, and a sample at microwave frequency has been fabricated and measured to validate our design. This simple band-stop plasmonic filter can find potential applications in plasmonic circuits and antennas at microwave and terahertz frequencies.