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In this article, a broadband radar cross section (RCS) reduction metasurface with a reconfigurable high-selectivity passband is proposed. Based on the equivalent circuit analysis, the feasibility of achieving the high-selective passband with multimode working state and RCS reduction near the passband through the combination of the checkerboard metasurface and the switchable bandpass frequency selective structure (FSS) is verified. The switchable FSS in the bottom layer can realize the function of wave transmittance/reflection by controlling the ON/OFF states of the p-i-n-diodes, and a novel staggered patch structure is introduced to realize the fast conversion between different working modes without using complex feeding networks. The checkerboard metasurface in the upper layer not only realizes the RCS reduction function through scattering cancellation but also improves the passband selectivity of the switchable FSS under different working modes. Finally, a prototype of the proposed structure is fabricated and measured. The measured results show that the proposed structure can be flexibly switched between the three working modes. In different working modes, the structure has a wide RCS reduction bandwidth and a high-selective passband.

Two-dimensional (2D) atomically thin quantum dots (QDs) possess extraordinary electrical and optical properties. However, fabricating high quality 2D QDs viaa universal and reliable technique remains a challenge. Here, we report a simple strategy to prepare high quality, monolayer single crystal 2D QDs viaultrathin cutting 2D bulk single crystals by ultramicrotome, followed by an exfoliation process. The as-prepared 2D QDs have pristine surface, high quality, high monolayer yield and high photoluminescence quantum yield (the highest photoluminescence quantum yield of WS2is 18%), which can be used as promising, low toxic, biocompatible, and good cell-permeability fluorescent labeling agents for in vitroimaging.