Customizing 2.5D Out‐of‐Plane Architectures for Robust Plasmonic Bound‐States‐in‐the‐Continuum Metasurfaces

Bound states in the continuum (BICs) have a superior ability to confine electromagnetic waves and enhance light–matter interactions. However, the quality‐factor of quasi‐BIC is extremely sensitive to structural perturbations, thus the BIC metasurfaces usually require a very‐high precision nanofabrication technique that greatly restricts their practical applications. Here, distinctive 2.5D out‐of‐plane architectures based plasmonic symmetry protected (SP)‐BIC metasurfaces are proposed, which could deliver robust quality factors even with large structural perturbations. The high‐throughput fabrication of such SP‐BIC metasurfaces is realized by using the binary‐pore anodic aluminum oxide template technique. Moreover, the deep neural network (DNN) is adapted to conduct multiparameter fittings, where the 2.5D hetero‐out‐of‐plane architectures with robust high quality‐factors and figures of merit are rapidly predicted and fabricated. Finally, owning to its large second‐order surface sensitivity, the desired 2.5D hetero‐out‐of‐plane architecture demonstrates a detection limit of endotoxin as low as 0.01 EU mL(‐1), showing a good perspective of biosensors and others.