A large-angle anomalous reflector based on a low-index polylactic acid metagrating is designed around 140 GHz. By breaking the limit of fixed bar-to-bar distance and directing the beam into the second diffraction order through the optimization of the 4π phase supercell, the efficiencies for 70° and 80° reflection under normal excitation both reach 0.82 with a wide bandwidth. In contrast, the efficiency is less than 0.2 in conventional designs. The success of the second-order low-index metagrating for large-angle deflection originates from the appropriate number of Bloch modes with well-engineered mode interactions and couplings. The design can be potentially fabricated by three-dimensional printing, with promising applications in designing flat lenses of high numerical aperture and extending the material system of metadevices.

中文翻译：

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用于大角度异常反射的低折射率二阶聚焦

在140 GHz附近设计了一个基于低折射率聚乳酸转移的大角度异常反射器。通过打破固定的棒到棒距离的限制，并通过优化4π相超级电池将光束定向到第二衍射级，在正常激发下70°和80°反射的效率在宽带宽下均达到0.82。相反，传统设计中的效率小于0.2。大角度偏转的二阶低折射率介质转换的成功源自适当数量的Bloch模式以及精心设计的模式相互作用和耦合。该设计可以通过三维印刷来制造，在设计具有高数值孔径的平面透镜和扩展元设备的材料系统方面具有广阔的应用前景。